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PubMed1996

[Constipation after tilidine/naloxone and tramadol in comparison to codeine. A dose response study in human volunteers].

Tramadol, a mixed mu-opioid agonist and a monoamine-reuptake blocking analgesic, has been supposed to have little effect on propulsive gastrointestinal motility. However, this has not been specifically studied in man. Following institutional approval, 18 human volunteers were given 50 mg of tramadol, tilidine/naloxone, and codeine, respectively, in a double-blind randomised cross-over design. Additionally, 12 further volunteers were given 100 mg of each opioid in a double-blind, randomised fashion, followed by measurement of gastrocoecal transit time. Gastrointestinal transit time was measured using the lactulose H(2)-breath test. A threefold increase in end-expiratory hydrogen when compared to the control value was considered the end point of gastrocoecal transit. At the low dose (50 mg) the three opioids did not differ significantly with regard to their effect on gastrointestinal motility. Gastrocoecal transit time was 90.8 (+/- 10.1 SEM) min for tramadol, 100.6 (+/- 9.8 SEM) min for tilidine/naloxone, and 104.2 (+/- 8.7 SEM) min for codeine. Doubling the dose of each opioid resulted in an increase in mean gastrocoecal transit, namely 97.8 (+/- 11.2 SEM) min for tramadol, 129.2 (+/- 12.2 SEM) min for tilidine/naloxone and 135.9 (+/- 9.2 SEM) min for codeine. The increase in gastrocoecal transit time was significant (P < 0.01) for high doses of tilidine/naloxone and codeine in contrast to the effect of the low doses. This lesser constipation effect may be due to the reduced affinity of tramadol to the mu-opioid receptor. Sedation was significantly higher for codeine after 50 mg (P < 0.05) and 100 mg (P < 0.005) than for tilidine/naloxone and tramadol. Vertigo was significantly higher after 50 mg (P < 0.05) and 100 mg (P < 0.005) of tilidine/naloxone and codeine than after tramadol. Perspiration was significantly higher after tramadol 100 mg (P < 0.005) than after tilidine/naloxone and codeine. Sedation is considered a typical symptom of analgesics interacting with centrally located opioid receptor sites. The higher incidence of perspiration after tramadol suggests that monominergic pathways may be involved in thermoregulation. In conclusion, the opioids tilidine/naloxone and codeine at the doses used significantly prolong gastrointestinal transit time in the high-dose range. Since tramadol does not induce a dose-related increase in gastrocoecal transit time, it may be a useful analgesic in patients who are prone to developing constipation during high-dose opioid therapy.

Clinical Trial↗
PubMed1999

Concentrations of morphine and codeine in urine of heroin abusers.

We have measured concentrations of morphine, codeine and 6-monoacetylmorphine in urine of people admitted to the Los Angeles County + University of Southern California Medical Center. Of 60 patients positive for morphine and/or codeine, 10 were judged to be heroin abusers based on positive results for 6-monoacetylmorphine, a specific metabolite of heroin. In nine of these ten patients, 0.028-39.4 microg/ml free codeine and 0.070-307 microg/ml total codeine were detected along with 1.74-218 microg/ml of free morphine and 11.2-2870 microg/ml of total morphine; the morphine-to-codeine ratios were 3.65-228 and 2.27-207 for the free forms and total amounts of these opiates, respectively. In the one patient who was negative for codeine, the concentrations of free and total morphine were 0.114 and 2.22 microg/ml, respectively. Based on our data and literature data available, the following criteria are proposed for judging heroin use from the results of urinalysis, especially when no 6-monoacetylmorphine is detected: (1) a detectable amount of free morphine exists and the concentration of total morphine is higher than 10 microg/ml; (2) a detectable amount of codeine exists; and (3) the morphine-to-codeine ratio is higher than 2 for both the free forms and total amounts of these opiates.

Journal Article↗
PubMed1992

The postoperative pharmacokinetics of codeine.

The metabolism and systemic availability of codeine have been studied in 12 patients after cholecystectomy. They were given 20 mg codeine as an IV bolus dose on the first day after surgery and 50 mg codeine as a single oral on the fourth day after surgery. Codeine had a medium to high extraction ratio and a total plasma clearance of 10.8 (4.3) ml.min-1.kg-1. The clearance varied four-fold between subjects. All the patients were extensive metabolizers with regard to the debrisoquine/sparteine polymorphism, as tested using dextromethorphan as the probe drug. Nevertheless, the formation of morphine from codeine was very small and plasma morphine concentrations were below the detection limit of 3.3 nmol.l-1 (1 ng.ml-1). As a corollary, the morphine/codeine ratio in the the concentration-time curves was less than 3% in all the patients. The systemic availability of codeine varied extensively between subjects (range 12-84%). This might partly explain differences in the dose of codeine required as an analgesic.

Adult↗
PubMed1982

Effects of a combination of oral naproxen sodium and codeine on experimentally induced pain.

The effect of an orally administered combination of naproxen sodium 550 mg and codeine phosphate 60 mg on threshold and tolerance to electrically induced pain, and on the threshold to thermally induced pain, was compared with the effects of naproxen sodium 550 mg alone, codeine phosphate 60 mg alone, and placebo. 16 female and 16 male, healthy young subjects, took part in four experiments on consecutive days of one week. On each day one treatment was administered, in random order, under double blind conditions. The combination increased threshold and tolerance to electrically induced pain and the threshold thermally induced pain markedly more than did naproxen sodium alone. Naproxen sodium plus codeine was also more effective in increasing threshold and tolerance to electrically induced pain than was codeine alone; the latter increased the threshold and tolerance to electrically induced pain and the threshold to thermally induced pain markedly more than placebo. Naproxen sodium alone had a relatively weak effect on the three pain measures. Reaction time to acoustic stimuli and the side effect profile were not significantly influenced by any of the treatments, and no severe adverse effects occurred. It is concluded that the combination of naproxen sodium 550 mg and codeine phosphate 60 mg, as indicated by its effects on experimentally induced pain, can produce more intense analgesia than the same doses of naproxen sodium and codeine administered alone, and that naproxen sodium and codeine phosphate given in combination enhanced each other's effect in an additive manner.

Adult↗
PubMedDate not supplied

Interaction of ethanol with codeine metabolism in rat hepatocytes: a multicompartmental model.

A multicompartmental pharmacokinetic model is presented, which based upon data from a previous study, describes the effects of ethanol (60 mM) on the metabolism of codeine (10 microM) in isolated rat hepatocytes. According to this model, about one third of codeine metabolized was transformed to morphine (13%) and norcodeine (18%), and two-thirds to unknown metabolites in the absence of ethanol. In the presence of ethanol, the apparent first order fractional rate of total codeine metabolism was reduced by 66% (0.0783 vs 0.0271 min-1). There was no alteration in the portion of codeine metabolized to norcodeine, but there was a 44% decrease in the fraction transformed to unknown metabolites and a tripling in the portion transformed to morphine. The fractional rate of codeine O-demethylation to morphine was apparently not sensitive to ethanol. In the absence of ethanol, about two-thirds of morphine was metabolized to morphine-3-glucuronide and the other third to unidentified metabolites. Only the glucuronidation process seemed to be inhibited by ethanol. The fractional rate of further metabolism of norcodeine to normorphine was similar in the absence or presence of ethanol. In conclusion ethanol co-incubation with codeine resulted in an inhibition of codeine conversion to unknown metabolites and norcodeine, and with morphine to morphine-3-glucuronide, but no inhibition in morphine production.

Animals↗
PubMed1997

The effect of codeine on gastrointestinal transit in extensive and poor metabolisers of debrisoquine.

METHODS: Codeine (50 mg) was administered to 12 extensive metabolisers (EM) and 12 poor metabolisers (PM) of debrisoquine. The oro-caecal transit time was estimated by the hydrogen breath test. The urinary excretion of codeine and metabolites during a 6-h interval was estimated after simultaneous analysis of codeine, morphine-3-glucuronide (M3G), morphine-6-glucuronide (M6G), morphine (M), normorphine (NM), norcodeine, norcodeine glucuronide and codeine-6-glucuronide using HPLC. RESULTS: The mean transit times after placebo were 1.3 h in the EM and 1.4 h in the PM. The corresponding figures after ingestion of codeine were 2.2 h and 2.1 h. The differences between the groups were statistically and clinically insignificant. The effect of codeine compared with placebo was significantly different in both groups. As expected, the metabolites of the O-demethylation pathway, M, M6G, M3G and NM were significantly lower in the PM. Interestingly, the recovery of the dose in the form of codeine (> 1.7 times) and norcodeine (> 2.5 times) was significantly higher in the PM, indicating compensatory metabolism via N-demethylation. CONCLUSION: In contrast to the analgesic effect, the prolongation of gastrointestinal transit caused by the drug does not depend on the formation of O-demethylated active metabolites M, M6G or NM.

Adult↗
PubMed1976

Radioimmunoassay for the simultaneous determination of morphine and codeine.

Antiserum against morphine was produced in rabbits immunized with morphine hapten conjugated to bovine serum albumin. The carrier protein was conjugated to the nitrogen atom of the opiate alkaloid in order to make the phenolic hydroxy group on C3 and the alcoholic group on C6 as determinant groups. The antibody does not recognize codeine or the major metabolite of morphine, 3-O-monoglucuronide. This antibody was used in conjunction with an antibody prepared against 3-O-carboxymethylmorphine to develop a radioimmunoassay which can measure codeine in the presence of morphine. The assay was used to follow both the plasma and brain levels of codeine and its biotransformation to morphine. Codeine when administered at a dose of 5 mg/kg i.v. showed a biphasic plasma decay curve the first phase of which had a +1/2 of 26 min. Peak concentrations of morphine were detected in the plasma following that dose of codeine at 0.5 h. 30 min after the injection of 20 mg/kg i.p. codeine, the brain levels of morphine were only 2% that of codeine. Thereafter, the brain levels of morphine slowly declined.

Animals↗
PubMedDate not supplied

Influence of hydrolysis procedures on the urinary concentrations of codeine and morphine in relation to doping analysis.

A method is described for the GC-NPD determination of urinary codeine and morphine after derivatization with trifluoroacetic anhydride. The lower limit for accurate quantitative determination was 0.05 microgram ml-1. After the oral administration of Bisolvon Griblettes corresponding to 30 mg codeine phosphate to seven subjects maximum codeine concentrations were obtained after 1-2 h and codeine remained detectable generally 24 h post dosing. The mean maximum level was 5.1 +/- 2.8 micrograms ml-1 found after enzymatic hydrolysis with Suc Helix pomatia juice (SHP). Based on these and previous results (mean 6.3 +/- 3.4 micrograms ml-1) a threshold level for codeine of 16 micrograms ml-1 is proposed. Significant differences were noticed between urinary codeine concentrations found after enzymatic hydrolysis with SHP, beta-glucuronidase from Patella vulgata and acid hydrolysis, respectively. Generally, highest values were obtained after SHP, while beta-glucuronidase and especially acid hydrolysis resulted in much lower levels. No morphine could be detected after acid hydrolysis. Concerning doping analysis, in particular the uniformity of methods and interpretation of the results, it is recommended that the hydrolysis method should be specified in the rules of those sporting federations allowing codeine and/or morphine.

Acetic Anhydrides↗
PubMed1996

Formation of morphine from codeine in Chinese subjects of different CYP2D6 genotypes.

Codeine and morphine pharmacokinetics among different CYP2D6 genotypes was compared in this study. Polymerase chain reaction tests were used to determine CYP2D6 genotypes in leukocyte deoxyribonucleic acid in 32 unrelated volunteers. Based on the genotypes, subjects were categorized into three groups: homozygous C/C188 (n = 8), heterozygous C/T188 (n = 12), and homozygous T/T188 (n = 12). Each subject was given a single oral dose of 30 mg codeine phosphate tablet after overnight fasting. Plasma concentration of codeine and 24-hour urinary morphine recovery were measured with HPLC. All three genotypes of subjects showed almost identical time profiles of plasma codeine. Urinary morphine glucuronide was hydrolyzed with beta-glucuronidase. The total recovered amount of morphine and glucuronides was 4349 +/- 646, 2564 +/- 242, and 1127 +/- 164 nmol (mean +/- SEM), respectively, for C/C188, C/T188, and T/T188 subjects (p < 0.05). The significant lower amount of urinary morphine but identical codeine plasma concentration suggested a lower partial clearance of the formation of morphine from codeine in T/T188 subjects. The results suggest a future study to assess the analgesic effect of codeine in different genotypes of CYP2D6 extensive metabolizers.

Adult↗
PubMed2003

The study of codeine-gluthetimide pharmacokinetic interaction in rats.

A high-performance liquid chromatographic (HPLC) assay with native fluorescence detection was developed for the simultaneous quantification of codeine and its two metabolites, morphine and morphine-3-glucuronide (M-3-G), in rat plasma. Solid-phase extraction was used to separate codeine and its metabolites from plasma constituents. Extraction efficiencies of codeine, morphine and M-3-G from rat plasma samples were 97, 92 and 93%, respectively. The chromatographic separation was performed using a reversed-phase C18 column and an elution gradient at ambient temperature. Using native fluorescence detection (excitation at 245 nm and emission at 345 nm), the detection limits of 50 ng/ml for morphine, 25 ng/ml for codeine and 20 ng/ml for M-3-G were obtained. The method had good precision, accuracy and linearity, and was applied to the study of glutethimide's influence on codeine metabolism in rat, following single doses of codeine-glutethimide association. The results confirmed the fact that glutethimide was responsible for a significant increase of morphine plasma levels and for their maintenance in time, concomitant with a significant decrease of M-3-G plasma levels, explained by the inhibition of morphine glucuronidation. In conclusion, glutethimide potentiates and prolongs the analgesic effect of codeine by a pharmacokinetic mechanism.

Animals↗
PubMed2005

Effect of alvimopan and codeine on gastrointestinal transit: a randomized controlled study.

UNLABELLED: background & aims: Opiate bowel dysfunction is a significant clinical problem. Our aim was to evaluate the ability of a peripheral mu-opioid antagonist, alvimopan, to reverse the effect of codeine on gastric, small-bowel, and colonic transit time in healthy volunteers. METHODS: Seventy-four healthy participants (43 women) were randomized in a double-blind, placebo-controlled manner to 1 of 4 groups: alvimopan 12 mg twice daily in the presence and absence of codeine sulfate 30 mg 4 times/day, or codeine or placebo alone. Gastric emptying, small-bowel, and colonic transit were measured by scintigraphy using a 99m-labeled technetium egg meal and 111-labeled indium charcoal delivered to the proximal colon via a delayed-release capsule. The primary end points for colonic transit were geometric center of the colonic counts at 24 hours and time for 50% ascending colon emptying. Analysis of covariance was used to assess the significance of the primary and secondary end points. RESULTS: Codeine delayed gastric, small-bowel, proximal, and overall colonic transit (P < .05). Alvimopan reversed codeine's effect on small bowel and colon (ascending colon and overall colonic transit). Alvimopan also accelerated overall colonic transit compared with placebo. Thus, the mean colonic geometric center at 24 hours was 2.33 with placebo/placebo, 3.25 with alvimopan/placebo (P < .05), 1.5 with placebo/codeine (P < .05), and 2.63 with alvimopan/codeine. Alvimopan did not reverse codeine's delay of gastric emptying. CONCLUSIONS: Alvimopan reverses codeine's inhibitory effect on small-bowel and colon transit and has potential for treatment of opiate bowel dysfunction. Alvimopan alone accelerates colonic transit, suggesting that mu-opiate mechanisms participate in the physiologic control of colonic transit.

Adolescent↗
PubMed1988

Pharmacokinetics and pharmacodynamics of codeine in end-stage renal disease.

The pharmacokinetics and pharmacodynamics of codeine and its metabolites codeine glucuronide, morphine, and morphine glucuronide were assessed after the administration of a single 60 mg oral dose of codeine sulfate and a single 60 mg intravenous dose of codeine phosphate in six healthy volunteers and six patients on chronic hemodialysis. Plasma and urine drug and metabolite concentrations were determined by sensitive and specific RIA procedures. Pharmacodynamics were assessed by pupillometry and vital sign determinations. Codeine elimination half-life and mean residence time were increased significantly in the hemodialysis group (18.69 +/- 9.03 hours and 12.77 +/- 7.09 hours, mean +/- SD, respectively) compared with the healthy volunteer group (4.04 +/- 0.60 hours and 3.90 +/- 0.52 hours, respectively). The total body clearance and volume of distribution of codeine were not significantly different between groups. Peak concentrations, times to peak concentrations, and AUCs for the three metabolites were also not significantly different between the groups, in part as a result of significant interpatient variability in the hemodialysis group. Examination of pupillometry and vital sign data did not reveal clinically significant differences in pharmacodynamics between the groups. Adjustment of dosage regimen may be required in some patients with uremia receiving multiple-dose codeine therapy.

Adult↗
PubMed2006

Pharmacokinetics of codeine and its metabolite morphine in ultra-rapid metabolizers due to CYP2D6 duplication.

Codeine is an analgesic drug acting on mu-opiate receptors predominantly via its metabolite morphine, which is formed almost exclusively by the genetically polymorphic enzyme cytochrome P450 2D6 (CYP2D6). Whereas it is known that individuals lacking CYP2D6 activity (poor metabolizers, PM) suffer from poor analgesia from codeine, ultra-fast metabolizers (UM) due to the CYP2D6 gene duplication may experience exaggerated and even potentially dangerous opioidergic effects and no systematical study has been performed so far on this question. A single dose of 30 mg codeine was administered to 12 UM of CYP2D6 substrates carrying a CYP2D6 gene duplication, 11 extensive metabolizers (EM) and three PM. Genotyping was performed using polymerase chain reaction-restriction fragment length polymorphism methods and a single-base primer extension method for characterization of the gene-duplication alleles. Pharmacokinetics was measured over 24 h after drug intake and codeine and its metabolites in plasma and urine were analyzed by liquid chromatography with tandem mass spectrometry. Significant differences between the EM and UM groups were detected in areas under the plasma concentration versus time curves (AUCs) of morphine with a median (range) AUC of 11 (5-17) microg h l(-1) in EMs and 16 (10-24) microg h l(-1) in UM (P=0.02). In urine collected over 12 h, the metabolic ratios of the codeine+codeine-6-glucuronide divided by the sum of morphine+its glucuronides metabolites were 11 (6-17) in EMs and 9 (6-16) in UM (P=0.05). Ten of the 11 CYP2D6 UMs felt sedation (91%) compared to six (50%) of the 12 EMs (P=0.03). CYP2D6 genotypes predicting ultrarapid metabolism resulted in about 50% higher plasma concentrations of morphine and its glucuronides compared with the EM. No severe adverse effects were seen in the UMs in our study most likely because we used for safety reasons a low dose of only 30 mg. It might be good if physicians would know about the CYP2D6 duplication genotype of their patients before administering codeine.

Administration, Oral↗
PubMedDate not supplied

Comparison of butorphanol nasal spray and fiorinal with codeine in the treatment of migraine.

Butorphanol tartrate is a synthetic mixed agonist-antagonist opioid analgesic. Its transnasal dosage form, which may be self-administered when the use of an opioid analgesic is appropriate, was previously shown to provide rapid relief of migraine pain. In this double-blind, parallel-group, outpatient study, we compared butorphanol nasal spray 1 mg followed in 1 hour by an optional second 1-mg dose with the orally administered analgesic, Fiorinal with Codeine (one capsule containing butalbital 50 mg, caffeine 40 mg, aspirin 325 mg, and codeine phosphate 30 mg). Patients (N=321) were assigned by randomization to one of two treatment groups (butorphanol or Fiorinal with Codeine) and instructed to self-administer medication when migraine pain reached an intensity of moderate or severe and to record study-related events in a diary for 24 hours posttreatment. Efficacy analyses were performed on data from 275 patients who took study medication and returned a patient diary; 136 in the butorphanol group and 139 in the Fiorinal with Codeine group. During the first 2 hours after treatment, butorphanol was more effective than Fiorinal with Codeine in treating migraine pain as measured by pain intensity difference scores, percentage of responders (pain decreased to mild or none), percentage of pain-free patients, and degree of pain relief, with a more rapid time to onset of 15 minutes. A similar percentage of patients in the two groups used rescue medication during the first 4 hours, after which more butorphanol-treated than Fiorinal with Codeine-treated patients used rescue medication. Butorphanol patients had more side effects, less improvement in digestive symptoms, and less improvement in functional ability than Fiorinal with Codeine patients.

Administration, Intranasal↗
PubMed1999

Combining diclofenac with acetaminophen or acetaminophen-codeine after oral surgery: a randomized, double-blind single-dose study.

In a randomized double-blind study, 120 patients with moderate to strong pain after surgical removal of wisdom teeth were given the following in single oral doses: 100-mg enteric-coated diclofenac tablets; 1 g acetaminophen (INN, paracetamol); 1 g acetaminophen plus 60 mg codeine; 100-mg enteric-coated diclofenac tablets plus 1 g acetaminophen; or 100-mg enteric-coated diclofenac tablets plus 1 g acetaminophen plus 60 mg codeine. Patients recorded pain intensity and pain relief for 8 hours. Upside assay sensitivity was confirmed because acetaminophen plus codeine was superior to acetaminophen. Diclofenac plus acetaminophen with and without codeine had superior analgesic effect compared with diclofenac, acetaminophen, or acetaminophen plus codeine. Addition of 60 mg codeine increased the degree of side effects. These results support the clinical practice of combining diclofenac with acetaminophen for acute pain. Of clinical importance are superior and prolonged analgesia and fewer side effects after enteric-coated diclofenac tablets plus acetaminophen compared with acetaminophen plus codeine.

Acetaminophen↗
PubMed1995

Quantitative determination of codeine and its major metabolites in human hair by gas chromatography-positive ion chemical ionization mass spectrometry: a clinical application.

A highly sensitive method was developed for the quantitative analysis of codeine and morphine in human hair. After addition of deuterated internal standards, hair samples were digested overnight in 1N NaOH at 37 degrees C. Hydrolysis was performed on certain digests by addition of 1 mL 6N HCl. Digest solutions were extracted using a solid-phase procedure with Bond Elut Certify extraction columns. Derivatized extracts were analyzed on a Finnigan ion trap mass spectrometer (Magnum) in the positive ion chemical ionization mode using acetone as the reagent gas, helium as the carrier gas, and a DB-5 MS (30 m x 0.25-mm i.d.) capillary column. The assay was linear to 75 ng/mg (r = 0.99) and was capable of detecting 10 pg of codeine and morphine on-column. Intra-assay precision ranged from 8 to 20%. The method was used to quantitate codeine in human hair obtained from two male volunteers with dark brown to black hair after a single oral dose of 120 mg codeine phosphate liquid. Hair samples were plucked from the scalp for 28 days and then cut at the scalp. Codeine was detectable in 1-cm long hair (containing the bulb) at 12 h following the dose and remained detectable in the hair shaft for at least 8 weeks. Codeine metabolites were not detected in the hair of these two subjects. The method is currently being used in dose-response disposition studies to quantitate codeine and its major metabolites in human subjects.

Administration, Oral↗
PubMed1995

Storage temperature effect on the stability of morphine and codeine in urine.

Urine samples collected from one laboratory volunteer and five alleged heroin addicts are prepared (without preservatives) in 5-mL aliquots in glass culture tubes and stored at room, refrigerator, and freezer temperatures. Total morphine, total codeine, free morphine, and free codeine in these samples are analyzed at 30-day intervals for an 11-month period. Total morphine and total codeine concentration decreases are observed for all specimens in all storage conditions. For samples stored in the refrigerator and freezer, similar concentration decrease patterns are observed for total morphine and total codeine, and the decreases range from approximately 10 to 40%. The concentrations of free morphine and free codeine show slight but steady increases. For samples stored at room temperature, large decreases of total morphine are observed for three out of 10 specimens, and total codeine and total morphine concentrations (in seven other specimens) show a decrease pattern similar to that observed for the freezer and refrigerator storage conditions. Three concentration change patterns are observed for free morphine: The type I pattern follows the same decrease pattern observed for freezer and refrigerator storage conditions; the type II pattern shows free morphine increases (after 30-90 days of storage) that remain relatively high for the entire 11-month period; and the type III pattern shows initial increases, followed by gradual decreases to levels that are comparable with the specimens' respective initial concentrations. Free codeine concentrations show slight and steady increases for the entire 11-month period in all specimens.

Codeine↗
PubMedDate not supplied

Detection of codeine and phenobarbital in sweat collected with a sweat patch.

Six male and two female subjects participated in a clinical study to determine the time course, the cumulative excretion, the intrasubject variability, the influence of site application, and the concentrations of codeine or phenobarbital in sweat following administration of a single dose of the drug. The doses of codeine and phenobarbital were 90 and 100 mg. respectively. Sweat was collected by means of a Sudormed sweat patch. Patches were removed at specified times over 1 week, and the drug content was determined by gas chromatography-mass spectrometry using deuterated internal standards. Codeine was detectable at 1 h following the administration, and a plateau concentration was observed on the third day. The peak codeine concentration was observed during the 12-24-h period. Morphine was never detected in sweat. In contrast, phenobarbital was first observed 3 h after administration, and cumulative excretion was continual throughout the week. Intersubject variability was enormous, as the concentrations for the same dose were in a magnitude of 1-5. Concentrations were in the range of 2-127 and 0.5-33 ng per patch for codeine and phenobarbital, respectively. The influence of the site of patch application was evaluated by analysis of six patches, all removed at the same time (24 h) in two subjects receiving 90 mg codeine. Codeine concentrations differed by a magnitude of 1-3 according to the area of application: the upper arm, the back, and the ribs. These data suggest that the sweat patch technology can be useful for documenting drug use over a 1-week period of surveillance.

Administration, Oral↗