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High-performance liquid chromatographic analysis of codeine in syrups using ion-pair formation.

The chromatographic behavior of morphine, codeine, and ethylmorphine was examined using reversed-phase high-performance liquid chromatography and ion-pair formation. Alkyl sulfonates and sulfates significantly increased the retention times for these compounds. The carbon chain length of the pairing ions was linearly related to the log of the capacity factors of these amine drugs. A mechanism for the increased retention based on ion-pair formation in the mobile phase is proposed. The use of dioctyl sodium sulfosuccinate as a pairing ion for codeine is described, and a method utilizing this pairing ion was developed for the quantitation of codeine in syrups. This method was applied successfully to various syrups containing codeine or codeine phosphate.

Chromatography, High Pressure Liquid↗

Determination of codeine in human plasma by reverse-phase high-performance liquid chromatography.

A high-performance liquid chromatographic (HPLC) method for the determination of codeine in human plasma is described. The specific, precise, and sensitive method can be used to determine plasma codeine levels after administration of therapeutic doses of codeine. After purification on a C18 extraction column, codeine in the form of hydrochloride is eluted. After addition of the internal standard, the codeine is separated on a reverse-phase C18 column using a slightly alkaline mobile phase and is then determined by UV detection. The analysis takes 3.5 min per run; the limit of detection is approximately 3 micrograms/L for a 50-microL loop and 800 microL of plasma. The absolute recovery is 98.4 +/- 6.7% (n = 14) in the 10-300-micrograms/L range. Within the range, the calibration curve is linear.

Adult↗

Use of codeine analgesics in a general population. A Norwegian study of moderately strong analgesics.

The prescribing of controlled analgesics (codeine, buprenorphine and pentazocine preparations) was studied, using prescriptions from the three pharmacies in the municipality of Tromsø, Norway. All prescriptions dispensed during one year were analysed. The study sample comprised 3083 women (58%) and 2223 men (42%) between 10 and 99 years of age. About 8% of the population had obtained one or more prescriptions of controlled analgesics. Combined codeine preparations were by far the most frequently prescribed subgroups, and the average amount purchased during 1 year was 30 defined daily doses (DDD). The sporadic users were in the majority. A few users had purchased high amounts of controlled analgesics. The prevalence of use, the mean number of defined daily doses of analgesics, and the proportion of 'weekly' drug users was higher in women than men. The prevalence increased significantly with age, from 0.7 to 22.3% in women and from 0.5 to 14.1% in men. The mean number of DDD during one year also increased with age, from 12.6 to 50.6 DDD in women, and from 6.6 to 40.6 DDD in men. The users of buprenorphine and pentazocine differed in several aspects from the codeine users. The highest use of combined codeine preparations was seen in elderly people especially in women. Use of lower codeine doses or intermittent treatment with other drugs e.g. plain paracetamol in adequate doses, may be appropriate alternatives reducing the risk of adverse drug reactions such as nausea and constipation. Monitoring of prescribing and use of controlled analgesics according to certain criteria may uncover possible misuse.

Adolescent↗

The effect of quinidine on the analgesic effect of codeine.

We have studied the hypoalgesic effect of codeine (100 mg) after blocking the hepatic O-demethylation of codeine to morphine via the sparteine oxygenase (CYP2D6) by quinidine (200 mg). The study was performed in 16 extensive metabolizers of sparteine, using a double-blind, randomized, four-way, cross-over design. The treatments given at 3 h intervals during the four sessions were placebo/placebo, quinidine/placebo, placebo/codeine, and quinidine/codeine. We measured pinprick pain and pain tolerance thresholds to high energy argon laser stimuli before and 1, 2, and 3 h after codeine or placebo. After codeine and placebo, the peak plasma concentration of morphine was 6-62 (median 18) nmol.l-1. When quinidine pre-treatment was given, no morphine could be detected (less than 4 nmol.l-1) after codeine. The pin-prick pain thresholds were significantly increased after placebo/codeine, but not after quinidine/codeine compared with placebo/placebo. Both placebo/codeine and quinidine/codeine increased pain tolerance thresholds significantly. Quinidine/codeine and quinidine/placebo did not differ significantly for either pin-prick or tolerance pain thresholds. These results are compatible with local CYP2D6 mediated formation of morphine in the brain, not being blocked by quinidine. Alternatively, a hypoalgesic effect of quinidine might have confounded the results.

Adult↗

Comparative bioavailability study of codeine and ibuprofen after administration of the two products alone or in association to 24 healthy volunteers.

The study objective was to compare the bioavailability of codeine and ibuprofen after oral administration of the two drugs alone or in association. The study was performed in three different periods, each separated by a wash-out of 6 days. Plasma concentrations were measured in 24 healthy volunteers after administration of a single oral dose of codeine phosphate (25 mg) and/or ibuprofen (200 mg). Codeine and ibuprofen assays were performed using two different HPLC methods. The relative bioavailabilities of codeine and ibuprofen (alone or in association) were 106 +/- 24% (mean +/- sd) and 101 +/- 19%, respectively. The results obtained demonstrated that bioavailabilities of codeine and ibuprofen were not modified when the two drugs were administrated alone or in association.

Adult↗

Different effects of inhibitors on the O- and N-demethylation of codeine in human liver microsomes.

OBJECTIVE: The O- and N-demethylation of codeine is catalysed by CYP2D6 and CYP3A4 respectively. The formation rates of morphine by O-demethylation and norcodeine by N-demethylation were studied in two sets of human liver microsomes. RESULTS: Relatively high K(m) values were found for both O- and N-demethylations, suggesting a low affinity to the corresponding enzymes. The inhibitory effects of various drugs were found to be different for O- and N-demethylations. The substrates of CYP2D6 such as thioridazine, amitriptyline and metoprolol inhibited the O-demethylation of codeine preferentially, while the substrates of CYP3A4 such as cyclosporine A, midazolam and erythromycin were all strong inhibitors of the N-demethylation of codeine. Quinidine and lignocaine, although they are substrates of CYP3A, showed preferential inhibition over the O-demethylation of codeine, suggesting a low affinity to the CYP3A. Methadone and dextropropoxyphene showed a preferential inhibition of CYP2D6 over CYP3A, while theophylline did not inhibit the O- or N-demethylation to a greater extent. CONCLUSION: It seems that there was a good correspondence between the capacity of drugs to inhibit the O- and N-demethylation of codeine in human liver microsomes and their apparent metabolism by CYP2D6 or CYP3A4, respectively in vivo in man, suggesting that this in vitro inhibition test may be a useful screen for drugs which interact with these two important drug-metabolising enzymes.

Codeine↗

Effect of codeine on oro-cecal transit time in Chinese healthy volunteers in comparison with Caucasian subjects.

OBJECTIVES: To evaluate the effect of codeine on oro-cecal transit time (OCTT) in Chinese subjects. METHODS: OCTT was measured with the hydrogen breath test in 12 Chinese healthy volunteers on two occasions: after placebo and after a single oral dose of codeine 50 mg. Codeine and its metabolites in urine were measured by HPLC. The Results of this study were compared with those previously obtained from Caucasian subjects. RESULTS AND CONCLUSION: The mean OCTT increased significantly after a single oral dose of codeine 50 mg [2.6 (1.2) h] compared with placebo [1.9 (0.6) h] in the Chinese subjects (P = 0.05). The increase in OCTT after codeine was similar in the Caucasian [0.9 (0.8) h] and in the Chinese subjects [0.7 (0.9) h]. However, the Chinese subjects had a significantly longer OCTT after placebo [1.9 (0.6) h] compared with the Caucasian subjects [1.3 (0.6) h, P < 0.05], possibly due to different environmental factors.

Adult↗

Codeine and 6-acetylcodeine analgesia in mice.

1. Acetylation of morphine at the 6-position changes its pharmacology. To see if similar changes are seen with codeine, we examined the analgesic actions of codeine and 6-acetylcodeine. 2. Like codeine, 6-acetylcodeine is an effective analgesic systemically, supraspinally and spinally, with a potency approximately a third that of codeine. 3. The sensitivity of 6-acetylcodeine analgesia to the mu-selective antagonists beta-FNA and naloxonazine confirmed its classification as a mu opioid. However, it differed from the other mu analgesics in other paradigms. 4. Antisense mapping revealed the sensitivity of 6-acetylcodeine to probes targeting exons 1 and 2 of the mu opioid receptor gene (Oprm), a profile distinct from either codeine or morphine. Although heroin analgesia also is sensitive to antisense targeting exons 1 and 2, heroin analgesia also is sensitive to the antagonist 3-O-methylnaltrexone, while 6-acetylcodeine analgesia is not. 5. Thus, 6-acetylcodeine is an effective mu opioid analgesic with a distinct pharmacological profile.

Analgesia↗

Comparative study of flurbiprofen, zomepirac sodium, acetaminophen plus codeine, and acetaminophen for the relief of postsurgical dental pain.

The relative analgesic efficacy and safety of single oral doses of 50 and 100 mg of flurbiprofen (Ansaid, Upjohn) were compared with 100 mg of zomepirac sodium, 650 mg of acetaminophen plus 60 mg of codeine, 650 mg of acetaminophen alone, and placebo in a randomized, double-blind, parallel-group study. A total of 182 patients entered the study with moderate pain from a third molar extraction and were evaluated for six hours. For many efficacy variables, all active treatments were significantly (p less than or equal to 0.05) more effective than placebo. The two doses of flurbiprofen gave approximately similar results, suggesting a plateau effect above 50 mg. With the exception of relief at one hour, there were no significant differences between zomepirac and either dose of flurbiprofen. However, the mean response with zomepirac was greater than with either 50 or 100 mg of flurbiprofen during the first four hours and lower during the last two hours. The analgesic effects of acetaminophen alone were not significantly different from acetaminophen in combination with codeine. At the first hour, acetaminophen plus codeine led to significantly better pain relief than did 100 mg of flurbiprofen. After the first hour, flurbiprofen resulted in greater mean scores than acetaminophen alone or acetaminophen plus codeine, and these differences were significant at the fifth and sixth hours. Five patients had adverse reactions while receiving acetaminophen, acetaminophen plus codeine, or placebo. There were no adverse effects with flurbiprofen or zomepirac.

Acetaminophen↗

In vitro formation of codeinone from codeine by rat or guinea pig liver homogenate and its acute toxicity in mice.

In vitro metabolism of codeine was investigated by using a 9000 g supernatant fraction of rat or guinea pig liver homogenate. When a mixture of [N-14CH3] and [C-6-3H]codeine was incubated with the rat liver 9000 g supernatant fraction in the presence of NAD, formation of codeinone, morphine and norcodeine was detected. Replacement of NAD with NADP abolished only the formation of codeinone. On the other hand, when the guinea pig liver homogenate was used in the presence of NAD, codeinone was the main metabolite of codeine. NADP was also ineffective in forming codeinone with the guinea pig liver homogenate. The acute toxicity of codeinone was thirty times higher than that of codeine. The roles of codeinone as a metabolic intermediate and in the acute toxicity of codeine are discussed.

Animals↗

Effects of chronic administration of codeine and promethazine on breathlessness and exercise tolerance in patients with chronic airflow obstruction.

It has been reported that short-term treatment with relatively high doses of opiates or promethazine causes improvements in dyspnoea and exercise tolerance in patients with chronic airflow obstruction (CAO). This study was designed to determine whether initial benefits were sustained during chronic administration of codeine or promethazine and to compare the two drugs in terms of their efficacy and possible mechanisms of action. Eleven patients with stable CAO were entered into a double-blind, randomized cross-over trial in which codeine (30 mg four times daily) or promethazine (25 mg four times daily) were orally administered for 1-month periods. Treatment effects were assessed by spirometry, arterial blood gases, 12-minute walk distance and subjective dyspnoea ratings. A statistically significant increase from the baseline in mean arterial PCO2 at at 24 hours (P less than 0.01) and at 1 month (P less than 0.05) occurred with codeine administration. There was no significant change from baseline for any other measurement with either drug, and no differences were detected between the two treatment arms. Four of the eleven patients did not complete the study; three of the four experienced worsening of their CAO requiring hospitalization (two while receiving codeine, one while receiving promethazine). We conclude that chronic treatment with either codeine or promethazine provides uncertain benefits to patients with CAO which may not outweigh potential risks.

Aged↗

Effects of response-contingent clock stimuli on behavior maintained by intravenous codeine in the rhesus monkey.

Response-contingent brief presentations of clock stimuli differentially correlated with food availability altered rates of codeine-maintained lever pressing. Rhesus monkeys performed under a two lever multiple schedule: Multiple fixed interval clock 5 min variable interval 2 min. Different colored lights were presented during successive 75 sec period of the fixed-interval clock component. Lever pressing under the FI Clock schedule was maintained by presentation of 1 g Noyes pellets, and lever pressing under the VI schedule by 0.05 mg/kg infusions of codeine PO4. Characteristic schedule-controlled performance developed in both schedule components. When the clock stimulus from the first or the final period of the FI Clock schedule was presented contingent upon completion of a short fixed ratio of responses during the variable-interval schedule component, the first clock stimulus decreased and the final clock stimulus increased rates of codeine-maintained lever pressing. Neither the first nor the final clock stimulus altered the frequency of codeine injection. The effect of each clock stimulus was accentuated by increasing the duration of stimulus presentation and by decreasing the response requirement for stimulus illumination. These rate-altering effects of the clock stimuli were most pronounced when different reinforcers were presented in the two components of the multiple schedule when either food or intravenous codeine injection was available under both components of the multiple schedule, response-contingent clock stimulus presentation did not alter response rates under the VI schedule.

Animals↗

Effect of codeine and oxazepam on afternoon cortisol secretion in men.

The objective of this study was to investigate the effects of oral codeine and oxazepam on afternoon cortisol secretion. Nine subjects received either oxazepam (30 mg) or codeine (30 mg) or placebo at 1700h on separate days in a counterbalanced design; the subjects were not aware of the sequence. Blood samples were collected with an indwelling intravenous catheter at 30-min intervals from 1500h to 1630h. Codeine, but not oxazepam, suppressed cortisol secretion. The trend of the declining cortisol values following codeine was significantly linear. These results are consistent with other evidence indicating the presence of an inhibitory opioid mechanism in the human hypothalamo-pituitary-adrenal (HPA) axis. The cortisol response to codeine may be a reliable and potentially useful paradigm for the study of the role of opioidergic mechanisms in HPA axis dysfunction.

Adult↗

Direct determination of codeine, norcodeine, morphine and normorphine with their corresponding O-glucuronide conjugates by high-performance liquid chromatography with electrochemical detection.

A high-performance liquid chromatographic method has been developed for the detection, separation and measurement of codeine and its metabolites norcodeine, morphine and normorphine, with their glucuronide conjugates. The glucuronidase Escherichia coli type VIIA hydrolyses codeine-6-glucuronide completely and is used for the construction of the calibration curves of codeine-6-glucuronide. Enzymic hydrolysis of codeine-6-glucuronide depends on the specific activity of the glucuronidase applied. Examples are shown of a volunteer who is able to form morphine from codeine and one who is unable to do so.

Chromatography, High Pressure Liquid↗

Determination of codeine and metabolites in plasma and urine using ion-pair high-performance liquid chromatography.

A reversed-phase ion-pair high-performance liquid chromatographic method for the simultaneous determination of codeine and seven metabolites is described. The samples are purified by reversed-phase solid-phase extraction. Codeine, norcodeine, codeine-6-glucuronide, norcodeine-6-glucuronide and morphine-3-glucuronide are measured with UV detection. Detection limits are 3 nmol/l (morphine-3-glucuronide) to 20 nmol/l (codeine). Morphine, normorphine and morphine-6-glucuronide are measured with electrochemical detection. Detection limits are 0.4 nmol/1 (morphine-6-glucuronide) to 1.0 nmol/l (normorphine). Correlation coefficients better than 0.998 are normally obtained for all compounds. The method was applied to the determination of the kinetics of codeine and its metabolites in plasma and urine samples from healthy volunteers.

Calibration↗

Effect of lambda-carrageenan-induced inflammatory pain on brain uptake of codeine and antinociception.

This study investigated the potential clinical implications of lambda-carrageenan-induced inflammatory pain on brain uptake of a commonly used analgesic, codeine, in relation to the fundamental properties of the blood-brain barrier (BBB) correlated to its antinociceptive profile over a 168-h time course. BBB uptake of [14C]sucrose (a membrane impermeant marker) and [3H]codeine were investigated using an in situ brain perfusion model in the rat. Results demonstrated a significantly increased brain uptake of [14C]sucrose at 1, 3, 6 and 48 h (139+/-9%, 166+/-19%, 138+/-13% and 146+/-7% compared with control, respectively) and [3H]codeine at 3 and 48 h (179+/-6% and 179+/-12% compared with control, respectively). Capillary depletion analyses ensured that increased radioisotope associated with the brain was due to increased uptake rather than trapping in the cerebral vasculature. Antinociception studies using a radiant-heat tail flick analgesia method demonstrated that lambda-carrageenan-induced inflammatory pain enhanced the in vivo antinociceptive profile of i.p.-administered codeine (7 mg/kg) at 3 and 48 h (144+/-11% and 155+/-9% compared with control, respectively). This study demonstrated that brain uptake and antinociception of codeine are increased during lambda-carrageenan-induced inflammatory pain, suggesting that the presence of inflammatory pain may be an important consideration in therapeutic drug dosing, potential adverse effects and/or neurotoxicity.

Analgesics, Opioid↗

Time course of the enhancement and restoration of the analgesic efficacy of codeine and morphine by delta9-tetrahydrocannabinol.

Delta9-tetrahydrocannabinol (delta9-THC) synergizes with morphine and codeine by releasing endogenous opioids. These studies determined 1) the duration of enhancement of morphine and codeine by delta9-THC, 2) the effect of (delta9-THC on the time course of fully efficacious doses of the opioids, 3) restoration of efficacy of morphine and codeine by delta9-THC, and 4) duration of restoration. Sub-active combination doses of delta9-THC/morphine or delta9-THC/codeine are equivalent in duration of action and efficacy to high-dose opioids alone. Delta9-THC (20 mg/kg p.o.) significantly restores the antinociceptive effects of both high-dose morphine and codeine (100 and 200 mg/kg p.o., respectively) at later time points at which morphine or codeine was no longer active (360- and 120-min post-administration, respectively). Thus, the cannabinoid/opioid combination might be useful in therapeutics to enhance opioid activity, as well as to restore the efficacy of opioids.

Analgesics, Non-Narcotic↗

Comparative actions of the opioid analgesics morphine, methadone and codeine in rat models of peripheral and central neuropathic pain.

Controversy persists in relation to the analgesic efficacy of opioids in neuropathic pain. In the present study the effects of acute, subcutaneous administration of the mu-opioid receptor agonists morphine, methadone and codeine were examined in rat models of peripheral and central neuropathic pain. In the spared nerve injury (SNI) and chronic constriction injury (CCI) models of peripheral neuropathic pain, both morphine (6mg/kg) and methadone (3mg/kg) attenuated mechanical allodynia, mechanical hyperalgesia and cold allodynia for up to 1.5h post-injection (P<0.05); codeine (30mg/kg) minimally alleviated mechanical hypersensitivity in SNI, but not CCI rats. When administered to rats with photochemically-induced spinal cord injury (SCI), morphine (2 and 6mg/kg) and methadone (0.5-3mg/kg) robustly attenuated mechanical and cold allodynia for at least 2h post-injection (P<0.05). Codeine (10 and 30mg/kg) also attenuated mechanical and cold allodynia in this model for at least 3h after injection. The magnitude of opioid-mediated antinociception was similar between SNI, SCI and non-injured rats as measured in the tail flick test. At antinociceptive doses, no motor impairment as determined by the rotarod test was observed. The therapeutic window (based on antiallodynia versus ataxia) obtained for codeine, was vastly superior to that obtained with morphine or methadone in SNI and SCI rats. Furthermore, the therapeutic window for codeine in SCI rats was 4-fold greater than in SNI rats. Our results further support the efficacy of mu-opioid receptor agonists in alleviating signs of neuropathic pain in animal models of peripheral and especially central nerve injury.

Analgesics, Opioid↗