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Disposition and metabolism of codeine after single and chronic doses in one poor and seven extensive metabolisers.

1. The pharmacokinetics, metabolism and partial clearances of codeine to morphine, norcodeine and codeine-6-glucuronide after single (30 mg) and chronic (30 mg 8 h for seven doses) administration of codeine were studied in eight subjects (seven extensive and one poor metaboliser of dextromethorphan). Codeine, codeine-6-glucuronide, morphine and norcodeine were measured by high performance liquid chromatographic assays. 2. After the single dose, the time to achieve maximum plasma codeine concentrations was 0.97 +/- 0.31 h (mean +/- s.d.) and for codeine-6-glucuronide it was 1.28 +/- 0.49 h. The plasma AUC of codeine-6-glucuronide was 15.8 +/- 4.5 times higher than that of codeine. The AUC of codeine in saliva was 3.4 +/- 1.1 times higher than that in plasma. The elimination half-life of codeine was 3.2 +/- 0.3 h and that of codeine-6-glucuronide was 3.2 +/- 0.9 h. 3. The renal clearance of codeine was 183 +/- 59 ml min-1 and was inversely correlated with urine pH (r = 0.81). These data suggest that codeine undergoes filtration at the glomerulus, tubular secretion and passive reabsorption. The renal clearance of codeine-6-glucuronide was 55 +/- 21 ml min-1, and was not correlated with urine pH. Its binding to human plasma was less than 10%. These data suggest that codeine-6-glucuronide undergoes filtration at the glomerulus and tubular reabsorption. This latter process is unlikely to be passive. 4. After chronic dosing, the pharmacokinetics of codeine and codeine-6-glucuronide were not significantly different from the single dose pharmacokinetics. 5. After the single dose, 86.1 +/- 11.4% of the dose was recovered in urine, of which 59.8 +/- 10.3% was codeine-6-glucuronide, 7.1 +/- 1.1% was total morphine, 6.9 +/- 2.1% was total norcodeine and 11.8 +/- 3.9% was unchanged codeine. These recoveries were not significantly different (P greater than 0.05) after chronic administration. 6. After the single dose, the partial clearance to morphine was 137 +/- 31 ml min-1 in the seven extensive metabolisers and 8 ml min-1 in the poor metaboliser; to norcodeine the values were 103 +/- 33 ml min-1 and 90 ml min-1; to codeine-6-glucuronide the values were 914 +/- 129 ml min-1 and 971 ml min-1; and intrinsic clearance was 1568 +/- 103 ml min-1 and 1450 ml min-1. These values were not significantly (P greater than 0.05) altered by chronic administration.(ABSTRACT TRUNCATED AT 400 WORDS)

Aged↗

NTP Toxicology and Carcinogenesis Studies of Codeine (CAS No. 76-57-3) in F344 Rats and B6C3F1 Mice (Feed Studies).

Codeine is used in a variety of pharmaceuticals including analgesics, sedatives, hypnotics, antiperistaltics, and antitussive agents. The National Cancer Institute and the Food and Drug Administration nominated codeine for study because it is a widely used drug and it is representative of the morphine class of compounds, for which chronic carcinogenicity studies had not been conducted. The oral route of administration was selected because it is the primary route of human exposure. Male and female F344/N rats and B6C3F1 mice were given codeine (99% pure) in feed for 14 days, 13 weeks, or 2 years. Genetic toxicology studies were conducted in Salmonella typhimurium and cultured Chinese hamster ovary cells. 14-DAY STUDY IN RATS: Groups of five male and five female F344/N rats were given 0, 1,562, 3,125, 6,250, 12,500, or 25,000 ppm codeine in feed for 14 days, which resulted in daily doses of approximately 125, 250, 450, 650, or 750 mg codeine/kg body weight to males and 125, 250, 500, 700, or 300 mg/kg to females. One female exposed to 6,250 ppm, one male and three females exposed to 12,500 ppm, and all males and females exposed to 25,000 ppm died during the study. Final mean body weights and mean body weight gains of all exposed groups except 1,562 ppm females were significantly lower than those of the controls. No chemical-related gross lesions were observed in rats at necropsy. Thickening of the forestomach mucosa (hyperplasia and hyperkeratosis) and lymphoid depletion of the thymus in exposed males and females and testicular degeneration in exposed males, observed primarily in the 12,500 and 25,000 ppm groups, were associated with decreased survival and increased morbidity in these groups. 14-DAY STUDY IN MICE: Groups of five male and five female B6C3F1 mice were given 0, 781, 1,562, 3,125, 6,250, or 12,500 ppm codeine in feed for 14 days, which resulted in daily doses of approximately 150, 300, 600, 1,300, or 3,000 mg codeine/kg body weight to males and 200, 400, 750, 1,500, or 3,000 mg/kg to females. All mice survived to the end of the study. The final mean body weight of 3,125 ppm females was significantly greater than that of the controls; the final mean body weight of 12,500 ppm females and the mean body weight gains of 12,500 ppm males and females were significantly lower than those of the controls. Absolute and relative liver weights of 3,125, 6,250, and 12,500 ppm males and of 12,500 ppm females and the absolute and relative right kidney weights of 12,500 ppm males were significantly lower than those of the controls. No gross or histopathologic lesions were attributed to codeine exposure. 13-WEEK STUDY IN RATS: Groups of 10 male and 10 female F344/N rats were given 0, 390, 781, 1,562, 3,125, or 6,250 ppm codeine in feed for 13 weeks, which resulted in daily doses of approximately 25, 50, 100, 200, or 450 mg codeine/kg body weight to males and 25, 50, 100, 250, or 500 mg/kg to females. There were no chemical-related deaths during the study. Final mean body weights and mean body weight gains of all groups of exposed males and of females exposed to 1,562, 3,125, and 6,250 ppm were significantly lower than those of the controls. Feed consumption decreased with increasing exposure concentration during the first week of the study; however, by the end of the study, feed consumption by most exposed groups was similar to that by the controls. There were alterations of various hematology and clinical chemistry parameters at the end of the study. There was a mild dose-dependent lymphopenia in females receiving 1,562 ppm and above and in 6,250 ppm males. There also was a minimal to mild macrocytosis that occurred in all exposed groups of males and in females exposed to 781, 3,125, or 6,250 ppm. No significant differences between control and exposed rats were observed in sperm morphology or vaginal cytology parameters. Absolute and relative adrenal gland weights of exposed males and of 3,125 and 6,250 ppm females were significantly greater than those of the controls. Absolute and relative liver weights of exposed males werees were significantly lower than those of the controls. Relative thymus weights of 3,125 and 6,250 ppm males were significantly lower than that of the controls. No chemical-related gross or histopathologic lesions were observed in male or female rats. 13-WEEK STUDY IN MICE: Groups of 10 male and 10 female B6C3F1 mice were given 0, 390, 781, 1,562, 3,125, or 6,250 ppm codeine in feed for 13 weeks, which resulted in daily doses of approximately 60, 120, 260, 460, or 1,000 mg codeine/kg body weight to males and 60, 130, 280, 530, or 1,200 mg/kg to females. Two male mice in the 3,125 ppm group died during week 7. All other mice survived to the end of the study. Final mean body weights of exposed males and females were similar to those of the controls. Feed consumption by exposed males and females was similar to that by the controls. Abnormal posture was observed in all exposed groups of males. There were no significant differences in hematology or urinalysis parameters in male or female mice. Minor, sporadic changes occurred in a few of the clinical chemistry parameters; they were not considered biologically significant. No significant differences in sperm morphology or vaginal cytology were attributed to codeine exposure. Absolute and relative kidney weights of 3,125 and 6,250 ppm males were lower than those of the controls. No chemical-related differences in organ weights were observed in females. No chemical-related gross or histopathologic lesions were observed in male or female mice. 2-YEAR STUDY IN RATS: Groups of 60 male and 60 female F344/N rats were fed diets containing 0, 400, 800, or 1,600 ppm codeine for up to 106 weeks, with 9 or 10 rats per group evaluated at 15 months. These exposure concentrations resulted in average daily doses of approximately 15, 30, and 70 mg codeine/kg body weight to males and 15, 40, and 80 mg/kg to females. Survival, Body Weights, Feed Consumption, and Clinical Findings Survival of 400 ppm females was significantly greater than that of the controls; survival of all groups of exposed males and of 800 and 1,600 ppm females was similar to that of the controls. There was an exposure-related decrease in mean body weights of males and females. The final mean body weight of 1,600 ppm males was 88% that of the controls, and the final mean body weight of 1,600 ppm females was 89% that of the controls. Feed consumption by exposed groups was similar to that by the controls. Chemical-related clinical findings were limited to ocular discharge in exposed males and females. Pathology Findings: Absolute and relative adrenal gland weights of 800 and 1,600 ppm males were significantly greater than those of the controls at 15 months. There were no increased incidences of neoplasms attributable to codeine exposure at any site. At 2 years, there were exposure-related decreases in the incidences of adrenal medulla hyperplasia in males and females. There was an exposure-related decrease in the incidence of benign pheochromocytomas in males, and the incidences in exposed males were significantly lower than that in the controls. In 1,600 ppm females the incidences of mammary gland fibroadenomas and of fibroadenomas or adenocarcinomas (combined) were significantly lower than those in the controls. The decreased incidences of benign pheochromocytomas in males and mammary gland neoplasms in females were considered to be related to codeine exposure. 2-YEAR STUDY IN MICE: Groups of 60 male and 60 female B6C3F1 mice were fed diets containing 0, 750, 1,500, or 3,000 ppm codeine for up to 106 weeks, with 9 or 10 mice per group evaluated at 15 months. These exposure concentrations resulted in average daily doses of approximately 100, 200, or 400 mg codeine/kg body weight to males and females. Survival, Body Weights, Feed Consumption, and Clinical Findings: Survival of exposed males and females was similar to that of the controls. Mean body weights of 750 and 1,500 ppm males and females were similar to those of the controls throughout most of the study. Mean body weights of 3,000 ppm males and females were less than those of the controls from about week 13, and the final mean body weights of these groups were 86% and 82% those of the respective controls. Feed consumption by exposed groups was similar to that by the controls. Pathology Findings: There were no increased incidences of neoplasms attributable to codeine exposure at any site. At 15 months, the incidence of thyroid gland follicular cell hyperplasia in 3,000 ppm males was significantly greater than that of the controls, and this lesion was observed in 1,500 and 3,000 ppm females. At 2 years, the incidences of follicular cell hyperplasia in all exposed groups of mice were significantly greater than those in the controls, but there were no increases in thyroid gland follicular cell neoplasms. The incidence of centrilobular fatty change in the liver of 3,000 ppm males was significantly lower than that in the controls at 15 months, and the decreased incidence appeared to be related to exposure level. At 2 years, the incidences of eosinophilic foci, foci of fatty change, centrilobular cytomegaly, and centrilobular fatty change in 3,000 ppm males were lower than those in the controls. The incidence of hepatocellular adenomas and the incidence of hepatocellular adenomas or carcinomas (combined) in 3,000 ppm males and females were significantly lower than those in the controls; this was considered to be related to lower body weights in these groups. GENETIC TOXICOLOGY: Codeine phosphate was not mutagenic in any of four strains of Salmonella typhimurium, with or without S9 metabolic activation enzymes. In cytogenetic tests with cultured Chinese hamster ovary cells, codeine phosphate induced dose-related increases in sister chromatid exchanges, with and without S9, only at concentration levels that caused cell cycle delay. No induction of chromosomal aberrations was noted in cultured Chinese hamster ovary cells treated with codeine phosphate, with or without S9. CONCLUSIONS: Under the conditions of these 2-year feed studies, there was no evidence of carcinogenic activity of codeine in male or female F344/N rats exposed to 400, 800, or 1,600 ppm. There was no evidence of carcinogenic activity of codeine in male or female B6C3F1 mice exposed to 750, 1,500, or 3,000 ppm. Thyroid gland follicular cell hyperplasia was increased in exposed male and female mice. Decreased incidences of benign pheochromocytomas of the adrenal medulla in male rats and mammary gland fibroadenomas and fibroadenomas or adenocarcinomas (combined) in female rats were related to codeine exposure. Synonyms: 7,8-didehydro-4,5-epoxy-3-methoxy-17-methylmorphinan-6-ol; methylmorphine; 3-0-methylmorphine monohydrate; N-methylnorcodeine; morphine-3-methyl ether; morphine monomethyl ether Trade names: Codeinum, Codicept, Coducept, Metilmorfina

Journal Article↗

Lack of effect of paracetamol on the pharmacokinetics and metabolism of codeine in man.

Plasma and urine concentrations of codeine and its measurable metabolites were determined by HPLC in six healthy subjects after a single 30 mg oral dose of codeine either alone or after 7 doses of 1 g paracetamol 8 hourly. After codeine alone, the t1/2 (h), AUC (mumol.l-1.h) and CLR (ml.min-1) for codeine were 2.2, 0.81, and 252 respectively. These were not significantly altered by paracetamol: 2.2, 0.84, and 291 respectively. For codeine-6-glucuronide the values were 2.4, 22.0, and 29.7 respectively. These were not significantly different from those after codeine plus paracetamol: 2.4, 21.9, and 39.6. There were no significant differences between the two treatments in the apparent partial clearances (ml.min-1) of codeine to morphine (88 codeine alone, 70 codeine plus paracetamol), to norcodeine (71 codeine alone, 88 codeine plus paracetamol), and to codeine-6-glucuronide (820 codeine alone, 1022 codeine plus paracetamol). The urinary excretion of codeine-6-glucuronide, morphine, norcodeine, and codeine were not significantly different between the two treatments.

Acetaminophen↗

Analgesic efficacy of an ibuprofen-codeine combination in patients with pain after removal of lower third molars.

A double-blind, randomised analgesic trial was carried out in 165 patients undergoing surgical removal of one impacted lower wisdom tooth. In a two-dose regimen, the analgesic efficacy of the combination ibuprofen-codeine 200 mg : 30 mg was compared with that of acetylsalicylic acid-codeine 500 mg : 30 mg and codeine 30 mg. Each dose was taken when the patient needed pain relief. The intensity of the pain was measured on a visual analogue scale during the 10-h period after the first dose. The mean pain reduction by Dose 1 in patients on ibuprofen-codeine, acetylsalicylic acid-codeine and codeine was 64%, 45% and 26%, respectively, and the mean duration of effect was 8.3, 6.3 and 5.6 h. According to the pain reduction, duration of effect and pain reduction index after Doses 1 and 1 + 2, there was a significant difference between ibuprofen-codeine and the other two drugs. The maximum pain reduction within 4 hours was 84% with ibuprofen-codeine. This was significantly different from the reduction achieved both with acetylsalicylic acid-codeine (64%) and codeine (35%). Seventeen patients reported adverse events: 5 on ibuprofen-codeine, 4 on acetylsalicylic acid-codeine and 8 on codeine. The most common events were tiredness and vertigo. It is concluded that the combination ibuprofen-codeine 200 mg : 30 mg had greater analgesic efficacy compared to the combination acetylsalicylic acid-codeine 500 mg : 30 or codeine 30 mg in patients with pain after removal of the lower third molars.

Adolescent↗

Same incidence of adverse drug events after codeine administration irrespective of the genetically determined differences in morphine formation.

The analgesic effect and adverse events of the weak opioid codeine is assumed to be mediated by its metabolite morphine. The cytochrome P-450 enzyme CYP2D6 catalysing the formation of morphine exhibits a genetic polymorphism. Two distinct phenotypes, the extensive (EMs) and poor metabolisers (PMs), are present in the population. The prevalence of PMs in the Caucasian population is 7% to 10%. Since PMs do not express functional CYP2D6, they have a severely impaired capacity to metabolise drugs which are substrates of this enzyme. Provided the analgesic effect and the adverse events of codeine are mediated by its metabolite morphine, large phenotype-related differences are to be expected and PMs, as they form only trace amounts of morphine, can serve as a model to test the hypothesis whether the analgesia and adverse events of codeine are mediated by the parent drug or its metabolite morphine. Therefore we have studied in a randomised placebo-controlled double-blind trial the analgesic effect of 170 mg codeine (p.o.) compared to 20 mg morphine (p.o.) and placebo in 9 EMs and 9 PMs using the cold pressor test. The duration and intensity of the side effects were assessed using visual analogue scales (VAS). Codeine and morphine concentrations were measured in serum and urine. Compared to placebo, 20 mg morphine caused a significant increase in pain tolerance in both phenotypes, EMs and PMs (16.2+/-27.4 vs. -0.66+/-27.4 s x h, n=18). However, following administration of codeine, analgesia was only observed in EMs but not in PMs (EMs: 54.9+/-42.2 vs. 1.7+/-4.2 s x h, P < 0.01; PMs: 9.6+/-10.9 vs. 3.3+/-23.7 s x h, not significant). Adverse events were significantly more pronounced after morphine and codeine compared to placebo in both EMs and PMs. In contrast to the phenotype-related differences in the analgesic effect of codeine, however, no difference in adverse events between the phenotypes could be observed. In the pharmacokinetic studies, significant differences between the two phenotypes in the formation of morphine after codeine administration could be observed. Whereas morphine plasma concentrations were similar in PMs (Cmax: 44+/-13 nmol/l: AUC: 199+/-45 nmol x h/l) and EMs (Cmax: 48+/-17 nmol/l); AUC: 210+/-65 nmol x h/l) after morphine administration, following 170 mg codeine, morphine plasma concentrations comparable to those after morphine application were only observed in EMs (Cmax: 38+/-16 nmol/l; AUC: 173+/-90 nmol x h/l). In PMs only traces of morphine could be detected in plasma (Cmax: 2+/-1 nmol/l; AUC: 10+/-7 nmol x h/l). The percentage of the codeine dose converted to morphine and its metabolites was 3.9% in EMs and 0.17% in PMs. The interindividual variability in analgesia of codeine which is related to genetically determined differences in the formation of morphine clearly indicate that this metabolite is responsible for the analgesic effect of codeine. In contrast to the analgesic effect, frequency and intensity of the adverse events did not present significant differences between the two phenotypes. These findings have implications for the clinical use of codeine. Since side effects occurred in both EM and PM subjects, the use of codeine as an analgesic will expose 7% to 10% of patients who are PMs to the side effects of the drug without providing any beneficial analgesic effects.

Adult↗

Identification of hydrocodone in human urine following controlled codeine administration.

Allegations of illicit hydrocodone use have been made against individuals who were taking physician-prescribed oral codeine but denied hydrocodone use. Drug detection was based on positive urine opiate immunoassay results with subsequent confirmation of hydrocodone by gas chromatography-mass spectrometry (GC-MS). In these cases, low concentrations of hydrocodone (approximately 100 ng/mL) were detected in urine specimens containing high concentrations of codeine (> 5000 ng/mL). Although hydrocodone has been reported to be a minor metabolite of codeine in humans, there has been little study of this unusual metabolic pathway. We investigated the occurrence of hydrocodone excretion in urine specimens of subjects who were administered codeine. In a controlled study, two African-American and three Caucasian male subjects were orally administered 60 mg/70 kg/day and 120 mg/70 kg/day of codeine sulfate on separate days. Urine specimens were collected prior to and for approximately 30-40 h following drug administration. In a second case study, a postoperative patient self-administered 960 mg/day (240 mg four times per day) of physician-prescribed oral codeine phosphate, and urine specimens were collected on the third day of the dosing regimen. Samples from both studies were extracted on copolymeric solid-phase columns and analyzed by GC-MS. In the controlled study, codeine was detected in the first post-drug-administration specimen from all subjects. Peak concentrations appeared at 2-5 h and ranged from 1475 to 61,695 ng/mL. Codeine was detected at concentrations above the 10-ng/mL limit of quantitation for the assay throughout the 40-h collection period. Hydrocodone was initially detected at 6-11 h following codeine administration and peaked at 10-18 h (32-135 ng/mL). Detection times for hydrocodone following oral codeine administration ranged from 6 h to the end of the collection period. Confirmation of hydrocodone in a urine specimen was always accompanied by codeine detection. Codeine and hydrocodone were detected in all specimens collected from the postoperative patient, and concentrations ranged from 2099 to 4020 and 47 to 129 ng/mL, respectively. Analyses of the codeine formulations administered to subjects revealed no hydrocodone present at the limit of detection of the assay (10 ng/mL). These data confirm that hydrocodone can be produced as a minor metabolite of codeine in humans and may be excreted in urine at concentrations as high as 11% of parent drug concentration. Consequently, the detection of minor amounts of hydrocodone in urine containing high concentrations of codeine should not be interpreted as evidence of hydrocodone abuse.

Administration, Oral↗

The effect of hair color on the incorporation of codeine into human hair.

The influence of melanin on the binding of xenobiotics in hair will impact the interpretation of drug concentrations determined by hair testing. The purpose of this study was to determine if codeine, as a model compound of abused drugs, would be incorporated into black, brown, blond, or red hair as a function of melanin concentration. Such data would assist in the interpretation of codeine concentrations in hair and help elucidate the potential influence of hair color on incorporation of drugs. Male and female Caucasians with black (n = 6), brown (n = 12), blond (n = 8), or red hair (n = 6) and non-Caucasians with black hair (n = 12) aged 21-40 years were enrolled in the study. Each subject was administered oral codeine phosphate syrup in a dosage of 30 mg three times a day for five days. Twenty-four hours after the end of the treatment period, a 30-mg codeine dose was administered and the subject's plasma area under the concentration time curve (AUC) for codeine was determined. Codeine and melanin were measured in the first 3 cm of hair closest to the vertex region of the scalp prior to and 1, 4, 5, 6, and 7 weeks after dosing. The quantitative and qualitative melanin profiles were determined for each subject's hair to provide an objective measure of hair color. The plasma concentrations of codeine were measured to eliminate differences in the bioavailability and clearance of codeine as factors that might account for the differences in codeine hair concentrations. The subjects were asked not to cut their hair in the vertex region of the scalp or to use any form of chemical treatment on their hair, but otherwise normal hygienic measures were permitted. The mean (+/- SE) hair codeine concentrations 5 weeks after dosing were 1429 (+/- 249) pg/mg in black hair; 208 (+/- 17) pg/mg in brown hair; 99 (+/- 10) pg/mg in blond hair; and 69 (+/- 11) in red hair pg/mg. In black hair, codeine concentrations were 2564 (+/- 170) pg/mg for Asians and 865 (+/- 162) pg/mg for Caucasians. Similar concentration relationships were observed at weeks 4, 6, and 7. A strong relationship between the hair concentrations of codeine and melanin (R(2) = 0.73) was observed. Normalization of the codeine concentration with the melanin concentration reduced the hair color differences observed. These data demonstrate that the interpretation and reporting of hair test results for codeine are influenced by hair color. After this dosing protocol, the proposed federal guideline cutoff of 200 pg/mg of codeine would result in 100% of subjects with black hair and 50% of subjects with brown hair being reported as positive, and subjects with blond or red hair would be reported as negative. The incorporation of these drugs into hair should be studied carefully in humans to ensure the appropriate interpretation of drug concentrations.

Administration, Oral↗

Efficacy of controlled-release codeine in chronic non-malignant pain: a randomized, placebo-controlled clinical trial.

Treatment decisions for the use of opioid analgesics in chronic non-malignant pain are based primarily on survey data, as evidence from well-controlled clinical trials has been lacking. Forty-six patients with chronic non-malignant pain were enrolled in a randomized, double-blind, placebo-controlled evaluation of controlled-release (CR) codeine. Following a 3-7-day diary familiarization period, patients were randomly assigned to 7 days of treatment each with CR codeine q12h or placebo. The CR codeine dose was determined from the consumption of acetaminophen+codeine in the 7 days preceding the study. During both phases, breakthrough pain was treated with acetaminophen+codeine every 4 h as required. Pain intensity was assessed at 08:00 h and 20:00 h using a visual analogue scale (VAS) and a 5-point categorical scale, and rescue analgesic consumption was recorded at the time of use. Thirty patients (17 female, 13 male; mean age: 55.1 +/- 13.4 years) completed the study and were treated with a mean daily CR codeine dose of 273 +/- 78 mg (range: 200-400 mg). CR codeine treatment resulted in significantly lower overall VAS pain intensity scores (35 +/- 18 vs. 49 +/- 16, P = 0.0001), categorical pain intensity scores (1.7 +/- 0.6 vs. 2.2 +/- 0.6, P = 0.0001), and in pain scores by day of treatment and by time of day. Daily rescue analgesic consumption was significantly lower on CR codeine, relative to placebo treatment (3.6 +/- 3.5 vs. 6.1 +/- 3.2 tablets/day, P = 0.0001). There was also a significant reduction in the Pain Disability Index (PDI) on CR codeine, compared to placebo (25.0 +/- 7.7 vs. 35.1 +/- 8.2, P = 0.0001). Patients' and investigators' blinded treatment preference was significantly in favor of CR codeine, relative to placebo (73% vs. 10%, P = 0.0160 and 80% vs. 7%, P = 0.0014, respectively). The incidence of nausea was significantly higher on CR codeine than on placebo (32.6% vs. 11.9%, P = 0.013). Ninety-three percent of patients completing the study requested long-term, open-label treatment with CR codeine. Pain intensity scores at the completion of 19 weeks of long-term evaluation were comparable to those during the double-blind CR codeine treatment. We conclude that treatment with CR codeine results in reduced pain and pain-related disability in patients with chronic non-malignant pain.

Acetaminophen↗

Disposition of codeine in female human hair after multiple-dose administration.

Studies of the disposition of codeine into the hair of female subjects (n = 7) were performed after a multiple-dose protocol. Caucasian female subjects with dark-brown-to-black hair were administered a total dose of 450 mg codeine over 5 days (30 mg was administered three times a day for 5 days). Analyses of codeine and metabolites in plasma, urine, and hair were performed by positive ion chemical ionization gas chromatography-mass spectrometry (GC-MS) on a Finnigan Magnum" mass spectrometer. Hair was plucked from the scalp for 5 weeks and subsequently cut from the scalp for up to 10 weeks. Prior to analysis, plucked hair specimens were cut into three segments: (a) a proximal, 1-cm segment, which contained the root, (b) the next distal, 3-cm segment, which was closest to the scalp, and (c) a segment containing all remaining hair to the natural hair tip. in female subjects, the mean (plus or minus standard error of the mean) hair concentration of codeine in the proximal, 1-cm segment from plucked hair was 2.7 ng/mg (+/- 0.55) at 12 h after the last codeine dose; 0.44 ng/mg (+/- 0.20) still remained in this segment at 5 weeks. Codeine was detected in the next 3-cm hair segment (above the scalp) at 1 week; the average codeine concentration for 10 weeks in the 3-cm, distal segment was 0.54 ng/mg (+/- O.05). No codeine was detected in the remaining hair segment (to the tip) at any time. In male subjects studied previously, the mean hair concentration of codeine in the proximal, 1-cm hair segment was 2.6 ng/mg (+/- 0.34) at 12 h after the last codeine dose, and no codeine was detected at 5 weeks. Codeine was not detected in the next 3-cm hair segment (above the scalp) until 3 weeks, and the average mean codeine concentration for 10 weeks was 0.09 ng/mg (+/- 0.01). Differences noted between male and female subjects in distal codeine hair concentrations were not explained by plasma pharmacokinetics.

Administration, Oral↗

Involvement of codeine in drug-related deaths.

The incidence and role of codeine in drug-related deaths in Victoria was investigated over a 5-year period. There were a total of 107 cases involving codeine, representing 8.8% of all drug-related deaths in this period in Victoria. There were only six fatalities in which codeine was considered the major poison. The mean (+/- SD) concentration of codeine in femoral blood was 4.0 +/- 2.3 mg/L (range, 2.1-8.0 mg/L). The mean concentration of free codeine was 1.3 +/- 0.9 mg/L (range, 0.4-2.8 mg/L). The remaining 101 cases involved a combination of codeine and other drugs. The mean total codeine blood concentration was 1.8 +/- 3.3 mg/L (range, 0.04-26 mg/L), which was significantly lower than in those cases where codeine was the major poison (p < 0.002). The mean concentration of free codeine was 0.82 +/- 4.9 mg/L (range, 0.02-9.0 mg/L), which was not significantly different (p > 0.05) from the six codeine-only cases. The most common drugs found in this group, other than codeine, were acetaminophen (62%), diazepam (46%), salicylate (20%), and ethanol (25%). The association of other psychoactive drugs in these deaths made the contribution of codeine difficult to assess. Free codeine concentrations > 0.4 mg/L and total codeine concentrations > 2.0 mg/L may be sufficient to cause death in the absence of any other contributing factors.

Acetaminophen↗

Evaluation of dosing guidelines for use of controlled-release codeine in chronic noncancer pain.

OBJECTIVE: The clinical utility of guidelines for conversion of patients from a combination analgesic preparation of acetaminophen 300 mg plus codeine 30 mg every 4h to 6h as needed to scheduled controlled-release (CR) codeine every 12h was evaluated. METHODS: Adult patients with chronic noncancer pain underwent a two-week evaluation on acetaminophen plus codeine, followed by eight weeks of treatment with CR codeine. Patients taking four to six tablets of acetaminophen plus codeine per day were transferred to 50 mg CR codeine every 12 h; those on seven to nine tablets were transferred to 100 mg every 12 h; those on 10 to 12 tablets were transferred to 150 mg every 12 h; and those on greater than 12 tablets were transferred to 200 mg every 12 h. Subsequent dose adjustments were permitted. Acetaminophen (325 mg) was available for rescue. Pain intensity (five-point categorical and 100 mm visual analog scale), pain related disability, adverse events and acceptability were assessed. RESULTS: Of the 140 patients enrolled, 95 completed eight weeks of treatment with CR codeine. During month 1 and month 2, the mean CR codeine daily doses were 295.7+/-119.1 mg and 390.3+/-163.4 mg, respectively. Pain scores during both CR codeine month 1 and 2 were significantly lower than on acetaminophen plus codeine (53.6+/-20.9 mm and 49.7+/-23.7 mm versus 59.6+/-17.5 mm; P=0.0003, P=0.0001, respectively). CR codeine treatment was rated as moderately or highly acceptable by 82% of patients compared with 50% for acetaminophen plus codeine (P=0.001). Only seven patients (5.9%) discontinued CR codeine treatment because of adverse events. CONCLUSION: The results confirm the safety, efficacy and patient acceptability of the initial conversion and maintenance dosing recommendations for CR codeine from a combination opioid/nonopioid analgesic.

Adult↗

Dose-related distribution of codeine and its metabolites into rat hair.

Drugs and endogenous compounds may be incorporated into the matrix of a growing hair shaft. However, the relationship between incorporation and dose or time course of plasma concentrations is poorly defined. The purpose of this study was to compare plasma and hair concentrations of codeine and its metabolites after various doses of codeine. Male Sprague-Dawley rats had a 1" x 1" square shaved from their backs. Codeine was administered by intraperitoneal injection (10, 20, 40, or 60 mg/kg/day) daily for 5 days. Fourteen days after beginning drug administration, the original patch was reshaved and newly grown hair was analyzed for codeine and morphine using GC/MS. The mean concentrations of codeine in hair for the 10, 20, 40, and 60 mg/kg/day groups were 0.29, 0.57, 0.96, and 1.93 ng/mg hair, respectively, and the concentrations of morphine were 0.15, 0.28, 0.49, and 0.79 ng/mg hair, respectively. The plasma concentration time courses for codeine and morphine were determined after single doses of either 20 or 40 mg/kg. Peak plasma codeine concentrations for the 20 and 40 mg/kg groups were 1,441 and 2,452 ng/ml plasma, respectively, and the areas under the plasma concentration vs. time curve were 699 and 1,581 ng-hr/ml, respectively. Morphine glucuronide, but not codeine glucuronide, was measured in the hair of rats administered codeine. Codeine was also administered to rats by constant intravenous infusion (40 mg/kg/day for 5 days). The concentration of codeine in rat hair after this route of administration was 2.92 +/- 0.72 ng/mg hair. Codeine and morphine are incorporated into rat hair in a dose-proportional fashion. Morphine glucuronide can be found in rat hair after codeine administration. The codeine concentration in hair is the same whether the drug is administered by constant intravenous infusion or daily intraperitoneal injections if the areas under the plasma concentration vs. time curve values are considered.

Animals↗

Time-dependent codeine hypoalgesia and hyperalgesia in domestic fowl.

Recent research demonstrated that codeine produced hypoalgesia and morphine produced hyperalgesia against a noxious thermal stimulus in young domestic fowl. The bidirectional effects of these opiate agonists on nociception are inconsistent with the notion that codeine's algesic effects result through in vivo demethylation of codeine to yield morphine. In Experiment 1, the temporal pattern (15,30,60 and 120 min) of codeine (30 mg/kg) effects on thermal nociception and respiration were examined in 15-day-old cockerels. Codeine produced a time-dependent biphasic response: hypoalgesia at 15 min and hyperalgesia at 60 and 120 min. Respiration was depressed by codeine at all test intervals. To assess for opioid specificity, Experiment 2 examined the action of naloxone (5 mg/kg) on the temporal pattern (15 and 60 min) of codeine effects (30 mg/kg) on thermal nociception and respiration. Bidirectional codeine algesic effects were observed at the 15- and 60-min test intervals. Naloxone increased the codeine jump latency scores at the 15-min interval and decreased codeine jump latency scores at the 60-min interval. These results suggest that codeine engages opposed nonopioid-mediated hypoalgesic and opioid-mediated hyperalgesic nociceptive systems in this animal model. Codeine depressed respiration at both the 15- and 60-min test intervals and this respiratory depression was reversed by naloxone. These findings support the notion that codeine respiratory effects are mediated by opioid system activity.

Animals↗

Randomized evaluation of controlled-release codeine and placebo in chronic cancer pain.

Codeine is widely used in combination with acetaminophen and aspirin for the management of mild to moderate pain. However, there are few controlled clinical trials of single-entity codeine in chronic cancer pain. The purpose of this study was to evaluate the clinical efficacy and safety of controlled-release codeine given every 12 hr in patients with cancer pain. Thirty-five patients with chronic cancer pain were randomized in a double-blind crossover study to controlled-release (CR) codeine or placebo, for 7 days each. Pain intensity was assessed at 0800 hr and 2000 hr using a visual analogue scale (VAS) and a five-point categorical scale, and the use of "rescue" acetaminophen-plus-codeine (300 mg/30 mg every 4 hr as needed) was recorded. Thirty patients completed the study (17 male, 13 female; mean age, 64.4 +/- 9.8 years) with a mean daily CR codeine dose of 277 +/- 77 mg (range, 200-400 mg). CR codeine treatment resulted in significantly lower overall VAS pain intensity scores (22 +/- 18 mm versus 36 +/- 20 mm, P = 0.0001), categorical pain intensity scores (1.2 +/- 0.8 versus 1.8 +/- 0.8, P = 0.0001), and pain scores when assessed by day of treatment and by time of day. Daily "rescue" analgesic consumption was significantly lower on CR codeine, compared to placebo treatment (2.2 +/- 2.3 versus 4.6 +/- 2.8 tablets per day, P = 0.0001). Both patients and investigators preferred CR codeine to placebo (80% versus 3%, P = 0.0014 and 73% versus 7%, P = 0.0160, respectively). These data indicate that CR codeine, given every 12 hr results in significant reductions in pain intensity and the use of "rescue" acetaminophen-plus-codeine in patients with cancer pain. CR codeine provides the benefits of a flexible single entity codeine formulation and the convenience of 12-hr duration of action, which allows patients uninterrupted sleep and improved compliance.

Aged↗

Characteristics of dependent and nondependent regular users of codeine.

Although codeine is a widely used medication, the problems of codeine abuse and dependence have not been well-studied. This study characterized regular codeine users (using at least 3 days per week for 6 months, excluding those using codeine for the treatment of cancer pain) through a self-completed questionnaire. Recruitment through newspaper advertisements resulted in a total of 339 eligible questionnaires. Thirty-seven percent of subjects met DSM-IV criteria for codeine dependence. Dependent subjects (mean age, 40 +/- 10 years) were using an average of 179 (+/-171) mg of codeine per day. Codeine was predominantly used in the form of combination products with acetaminophen. Dependent subjects identified specific problems causally related to their codeine use such as depression (23%), anxiety (21%), and gastrointestinal disturbances (13%). The dependent subjects reported problems with other drugs more than did nondependent users (alcohol, 57% vs. 26%; cannabis, 23% vs. 5%; sedative/hypnotics, 33% vs. 12%; and heroin, 11% vs. 2%, respectively). Most were taking codeine primarily for a chronic pain problem (81%), although the dependent subjects currently found codeine less effective for treating pain than did the nondependent subjects and were more likely to use codeine for pleasurable effects, to relax, or to prevent withdrawal symptoms. This study showed that dependence is associated with the regular use of codeine. Pain is a key issue with these users; however, they are probably not receiving optimal treatment. There is a need to identify individuals experiencing problems with their codeine use and to develop optimal prevention and treatment strategies.

Adolescent↗

Oral administration of codeine in the presence of ethanol: a pharmacokinetic study in man.

Three healthy male volunteers were given a codeine (1 mg/kg) solution in the absence and presence of ethanol in a cross-over designed study. The blood ethanol concentration was kept at approximately 16 mM for 8 hrs. Blood samples were taken at several occasions during the first day after the codeine administration. Urine was sampled during three days. There were no significant differences in the area under serum concentration versus time curve in the absence and presence of ethanol with respect to free codeine, total codeine and total morphine. The fraction of codeine glucuronized in serum (approximately 94%), the maximum serum concentration of free (0.34 microM) and total codeine (6.3 microM), the time to reach the maximum serum concentration values (approximately 65 min.) were also similar in the absence and presence of ethanol. The accumulated percentage of the codeine dose given which was found as codeine and morphine and their conjugates in the urine ranged from 50 to 91 percent in the different subjects. The accumulated percentage of the administered codeine dose found as free morphine in the urine, was significantly lower in the ethanol exposed individuals (0.18 +/- 0.03%) compared to the controls (0.39 +/- 0.09%). The percentage of the codeine dose found in the urine in the control situation as free codeine (5.2 +/- 2.2%) was not statistically different from the amount found in the urine after ethanol treatment (4.3 +/- 2.0%). The percentage glucuronized morphine (95.3 +/- 0.4%) and codeine (91.9 +/- 2.2%) in the urine in the absence of ethanol was similar to glucuronized morphine (95.3 +/- 2%) and codeine (93.1 +/- 3%) after ethanol exposure.(ABSTRACT TRUNCATED AT 250 WORDS)

Administration, Oral↗