Partial filling-micellar electrokinetic chromatography optimization studies of ibuprofen, codeine and degradation products, and coupling to mass spectrometry: part II

We describe the use of partial filling-micellar electrokinetic chromatography-mass spectrometry (PF-MEKC-MS) on the pharmaceutical ingredients ibuprofen and codeine phosphate as well as their degradation products and impurities. The study focuses on the change of the borate buffer to the volatile ammonium acetate and the optimization of critical MS parameters. The sensitivity of the method is also evaluated. The results are compared to an existing MEKC-UV method that is used for quantitative determination of the two main substances as well as for the analysis of the degradation products. It is concluded that the PF-MEKC-MS system is suitable for separation and identification.

Determination of drugs of abuse in hair: evaluation of external heroin contamination and risk of false positives

One of the most controversial point regarding the validity of hair testing is the risk of false positive due to external contamination. The aim of our experience is to verify if a 5 consecutive days contamination with a small amount of a powdered mixture of heroin hydrochloride and acetylcodeine hydrochloride (10:1 w/w) will last sufficiently long to make a contaminated subject indistinguishable from active users, and if normal washing practices together with the decontamination procedure are sufficient to completely remove the external contamination. Our results suggest that decontamination procedures are not sufficient to remove drugs penetrated into hair from external source. In fact, all contaminated subjects were positive for opiates (heroin, 6-MAM, morphine, acetylcodeine and codeine) for at least 3 months. Significant 6-MAM concentrations (>0.5 ng/mg) were found in each subject until 6th week. Further, 6-MAM/morphine ratio were always above 1.3.

Comparative biotransformation of morphine, codeine and pholcodine in rat hepatocytes: identification of a novel metabolite of pholcodine

1. Pholcodine (3-morpholinoethylmorphine), a semi-synthetic alkaloid, is widely used as an antitussive agent. 2. Norpholcodine [7,8-didehydro-4,5alpha-epoxy-3-(2-morpholinoethoxy)morphinan-6alpha-ol] (NP) and pholcodine-N-oxide [1(9a)-dehydro-(4aR,5S,7aR,9cS,12S)-4a,5,7a,8,9,9a-hexahydro-5-hydroxy-12-methyl-3-morpholinoethoxy-1H-8,9,c-(iminoethano)phenanthro[4,5-bcd] furan-12-oxide] (PNOX) were identified in incubations of pholcodine with freshly isolated rat hepatocytes by liquid chromatography/electrospray-mass spectrometry (LC/ESI-MS). 3. Synthesized NP and PNOX were characterized by mass spectrometry and nuclear magnetic resonance (NMR) spectroscopy. 4. N-oxidation was the major metabolic pathway for pholcodine, producing a previously unreported metabolite. 5. The metabolism of morphine and codeine was also determined using freshly isolated hepatocytes. 6. For morphine, 3-glucuronidation was the major metabolic pathway, whilst for codeine it was dealkylation (O- and N-). 7. Neither morphine nor its metabolites were metabolites of pholcodine. 8. This observation supports the hypothesis that the absence of analgesic activity with pholcodine may be due to less O-dealkylation in vivo. 9. Together with the slow biotransformation of pholcodine (k(met) = 0.021 microM min(-1)) in comparison with morphine (k(met) = 0.057 microM min(-1)) and codeine (k(met) = 0.112 microM min(-1)), the results obtained were consistent with its low addiction potential and suggest that its antitussive efficacy is mediated by the parent drug or one of its metabolites other than morphine.

Acetylcodeine as a urinary marker to differentiate the use of street heroin and pharmaceutical heroin

Acetylcodeine (ACOD) is a synthesis byproduct present in street heroin but not in pharmaceutical diacetylmorphine (DAM) as used in the Swiss program Heroin-Assisted Treatment for Opiate Dependent Drug Users (HAT). ACOD was evaluated and validated as an urine marker to detect the consumption of street heroin by HAT participants. A gas chromatography-mass spectrometry method allowing the quantitation of ACOD concentrations as low as 0.2 ng/mL urine has been developed. In opiate-naïve subjects, intravenous (i.v.) ACOD showed a plasma elimination half-life of 237 +/- 18 min, urine peak concentrations 2 h after administration, and a detection window of 8 h. Only 0.4 +/- 0.1% was excreted unchanged, with codeine (COD) as the main metabolite. ACOD may be formed by transacetylation when i.v. DAM and oral codeine are co-administered. To avoid false-positive results, the calculation of COD/ACOD ratios is recommended. In a study with 105 HAT participants, 14% of the tested urines were ACOD positive. Only a low correlation was found between the anonymously self-declared consumption of street heroin and the ACOD positive rate.

Plasma and oral fluid pharmacokinetics and pharmacodynamics after oral codeine administration

BACKGROUND

The ease, noninvasiveness, and safety of oral fluid collection have increased the use of this alternative matrix for drugs-of-abuse testing; however, few controlled drug administration data are available to aid in the interpretation of oral fluid results.

METHODS

Single oral codeine doses (60 and 120 mg/70 kg) were administered to 19 volunteers. Oral fluid and plasma were analyzed for free codeine, norcodeine, morphine, and normorphine by solid-phase extraction combined with gas chromatography-mass spectrometry (SPE/GC-MS). Physiologic and subjective effects were examined.

RESULTS

Mean (SE) peak codeine concentrations were 214.2 +/- 27.6 and 474.3 +/- 77.0 micro g/L in plasma and 638.4 +/- 64.4 and 1599.3 +/- 241.0 micro g/L in oral fluid. The oral fluid-to-plasma ratio for codeine was relatively constant ( approximately 4) from 1 to 12 h. The mean half-life (t(1/2)) of codeine was 2.2 +/- 0.10 h in plasma and 2.2 +/- 0.16 h in oral fluid. Significant dose-related miosis and increases in sedation, psychotomimetic effect, and "high" occurred after the high dose. Mean codeine oral fluid detection time was 21 h with a 2.5 microg/L cutoff, longer than that of plasma (12-16 h). Detection times with the proposed Substance Abuse and Mental Health Services Administration cutoff (40 microg/L) were only 7 h. Norcodeine, but not morphine or normorphine, was quantified in both plasma and oral fluid.

CONCLUSIONS

The disposition of codeine over time was similar in plasma and oral fluid, but because of high variability, oral fluid codeine concentrations did not reliably predict concurrent plasma concentrations. Oral fluid testing is a useful alternative matrix for monitoring codeine exposure with a detection window of 7-21 h for single doses, depending on cutoff concentrations. These controlled drug administration data should aid in the interpretation of oral fluid codeine results.

Affinities of dihydrocodeine and its metabolites to opioid receptors

Dihydrocodeine is metabolized to dihydromorphine, dihydrocodeine-6-O-, dihydromorphine-3-O- and dihydromorphine-6-O-glucuronide, and nordihydrocodeine. The current study was conducted to evaluate the affinities of dihydrocodeine and its metabolites to mu-, delta- and kappa-opioid receptors. Codeine, morphine, d,1-methadone and levomethadone were used as controls. Displacement binding experiments were carried out at the respective opioid receptor types using preparations of guinea pig cerebral cortex and the specific opioid agonists [5H]DAMGO (mu-opioid receptor), [3H]DPDPE (delta-opioid receptor) and [3H]U69,593 (K-opioid receptor) as radioactive ligands at concentrations of 0.5, 1.0 and 1.0 nmol/l, respectively. All substances had their greatest affinity to the mu-opioid receptor. The affinities of dihydromorphine and dihydromorphine-6-O-glucuronide were at least 70 times greater compared with dihydrocodeine (Ki 0.3 micromol/l), whereas the other metabolites yielded lower affinities. For the delta-opioid receptor, the order of affinities was similar with the exception that dihydrocodeine-6-O-glucuronide revealed a doubled affinity in relation to dihydrocodeine (Ki 5.9 micromol/l). In contrast, for the K-opioid receptor, dihydrocodeine-6-O- and dihydromorphine-6-O-glucuronide had clearly lower affinities compared to the respective parent compounds. The affinity of nordihydrocodeine was almost identical to that of dihydrocodeine (Ki 14 micromol/l), whereas dihydromorphine had a 60 times higher affinity. These results suggest that dihydromorphine and its 6-O-glucuronide may provide a relevant contribution to the pharmacological effects of dihydrocodeine. The O-demethylation of dihydrocodeine to dihydromorphine is mediated by the polymorphic cytochrome P-450 enzyme CYP2D6, resulting in different metabolic profiles in extensive and poor metabolizers. About 7% of the caucasian population which are CYP2D6 poor metabolizers thus may experience therapeutic failure after standard doses.

A rapid GC-MS method for the determination of dihydrocodeine, codeine, norcodeine, morphine, normorphine and 6-MAM in urine

The presence of the heroin metabolite 6-monoacetylmorphine (6-MAM) in urine is used to definitively identify recent heroin abuse. A rapid and sensitive GC-MS method for the simultaneous analysis of codeine, norcodeine, morphine, normorphine and 6-MAM in urine was developed and successfully applied to the analysis of 321 'heroin-positive' urine specimens from individual subjects (identified by the presence of 6-MAM), to provide quantitative urinary opiate excretion data for heroin abusers. The cohort analysed was composed of 238 males (age range 16-53 years) and 83 females (age range 16-50 years). The concentrations of free 6-MAM, morphine and codeine determined in these 321 specimens ranged between 103-246,312, 129-193,600 and 103-519,000 microg/l, respectively. Free norcodeine and normorphine concentrations were found to range between 143-50,200 and 205-149,700 microg/l, respectively. A statistically significant relationship was determined between the subject age and the 6-MAM concentration, possibly indicating opiate tolerance in these individuals.

Interpretation of GC-MS opiate results in the presence of pholcodine

Although the cross reactivity of pholcodine with opiate immunoassays has been well documented there is little published information the potential for pholcodine interference with chromatographic analyses. Wilson and Smith [Ann. Clin. Biochem. 36 (1999) 592] recently described the 'misidentification' of morphine in quality control specimens that had been spiked with pholcodine. This report describes a sensitive, rapid gas chromatography-mass spectrometry (GC-MS) method for the detection and quantitation of pholcodine and morphine, together with 6-monoacetylmorphine (6-MAM), codeine and dihydrocodeine in urine. This method was used to analyse urine specimens collected from volunteers given single and multiple doses of pholcodine to establish the significance this drug on the analytical results obtained when performing drug screening according to the proposed UK and EU legally defensible workplace drug testing guidelines. The maximum urinary free morphine concentration achieved following a single 10mg oral dose of pholcodine was 1.39 mg/l at 2-4h post dose. Following multiple 10mg oral doses of pholcodine the maximum urinary free morphine concentration was determined as 0.4 mg/l at 170 h after the final dose was administered. This apparent anomaly in the morphine concentrations obtained following single and multiple pholcodine doses can be explained in part by differences in the concentration of the specimens, and may be overcome by applying a correction factor for specimen dilution using their creatinine concentration. The data from this study suggests that even following one single 10mg dose of pholcodine, free morphine concentrations greater than both the proposed UK workplace drug testing guidelines threshold of 0.3mg/l total morphine and the proposed European Union threshold of 0.2mg/l total morphine can be achieved. This highlights the need for caution when interpreting confirmatory opiate data, especially in medicolegal and clinical cases, and in cases where the use of pholcodine is suspected.

Inhaled pinacidil, an ATP-sensitive K+ channel opener, and moguisteine have potent antitussive effects in guinea pigs

We investigated whether inhaled pinacidil and moguisteine inhibit capsaicin-induced coughs in guinea pigs. Inhaled pinacidil (15 - 60 microg/ml), an ATP-sensitive K+ channel opener, and moguisteine (15 - 60 microg/ml) each dose-dependently inhibited the number of capsaicin-induced coughs. The antitussive effects of pinacidil and moguisteine were significantly antagonized by pretreatment with glibenclamide (10 mg/kg, i.p.), an ATP-sensitive K+ channel blocker. However, pretreatment with naloxone methiodide (10 mg/kg, s.c.) had no significant effect on the antitussive effects of either pinacidil or moguisteine. On the other hand, inhaled dihydrocodeine (15 - 60 microg/ml) also dose-dependently suppressed the number of capsaicin-induced coughs. The antitussive effect of inhaled dihydrocodeine was significantly antagonized by pretreatment with naloxone methiodide (10 mg/kg, s.c.), but not by glibenclamide (10 mg/kg, i.p.). These results indicate that inhaled pinacidil and moguisteine both attenuate capsaicin-induced coughs. Pinacidil and moguisteine may exert their antitussive effects through the activation of ATP-sensitive K+ channels in the tracheobronchial tract. Furthermore, it is possible that ATP-sensitive K+ channels may be involved in the antitussive effects of peripherally acting non-narcotic antitussive drugs.

Diclofenac does not interact with codeine metabolism in vivo: a study in healthy volunteers

BACKGROUND

Previously, we have demonstrated a marked inhibition of codeine glucuronidation by diclofenac in human liver tissue homogenate. We therefore aimed to investigate whether diclofenac inhibits glucuronidation of codeine also in vivo in healthy volunteers.

METHODS

In a randomised, placebo-controlled, double-blind, cross-over study, 12 healthy volunteers received a singe of 100 mg codeine phosphate plus 50 mg diclofenac sodium or codeine phosphate plus placebo. Over a 36 hour period serum concentrations of codeine and its metabolites as well as urinary excretion were analysed using LC-mass spectrometry. Side effects were recorded and analgesic efficacy was determined using the cold pressor test (0-6 h).

RESULTS

A single dose of diclofenac did not alter the formation of codeine-6-glucuronide in healthy volunteers. Metabolic clearance of codeine to morphine was not affected by diclofenac. In terms of side effects, both treatments were well tolerated. Diclofenac did not significantly influence the analgesic effects of codeine in the cold pressor test.

CONCLUSIONS

In contrast to recent in vitro data, a single oral dose of diclofenac did not alter the glucuronidation of codeine in healthy volunteers.

Impurity profiling of pholcodine by liquid chromatography electrospray ionization mass spectrometry (LC-ESI-MS)

Previously, a dimorpholinoethyl pholcodine manufacturing impurity was reported to be present in some samples of pholcodine. Apart from this impurity and morphine, other unknown impurities were detected in all the samples analysed by HPLC and micellar electrokinetic capillary chromatography. In this study, liquid chromatography mass spectrometry (LC-MS) analysis of samples of pholcodine showed that two of the previously unidentified compounds had mass spectra with molecular ions which differed from pholcodine by 16 amu. From this observation and other experimental data it was concluded that they are hydroxy derivatives of pholcodine. 10-S-hydroxy-pholcodine, which was synthesized by the oxidation of pholcodine with chromic acid, had the same chromatographic properties as one of these compounds. An early eluting compound in the LC-MS chromatograms of pholcodine was identified as pholcodine-N-oxide by matching chromatographic and mass spectral data of a synthesized pholcodine-N-oxide standard. The reaction of pholcodine with m-chloroperoxybenzoic acid not only produced the mono N-oxide, but also pholcodine-di-N,N'-oxide.

Cell death-inducing activity of opiates in human oral tumor cell lines

In screening cytotoxic agents in morphine alkaloids [TE1-10], codeinone [TE8] was cytotoxic against two human oral tumor cells lines (HSC-2 and HSG). The cytotoxic activity of codeinone (CC50=1.0-1.2 microg/mL) against HSC-2 or HSG cells was higher than that of doxorubicin (CC50=1.9-2.0 microg/mL). Human oral gingival fibroblasts (HGF) were relatively resistant to codeinone, as judged by higher SI ratio (3.7) suggesting the tumor-selective cytotoxicity of codeinone. The cytotoxic activity of morphine (CC50=221 microg/mL) against HSC-2 was slightly lower than that of codeine (CC50=186 microg/mL), thebaine (CC50=125 microg/mL), etorphine (CC50=94 microg/mL) or dihydroetorphine (CC50=60 microg/mL). A study of structurally-related compounds suggested that the alpha,beta-unsaturated ketone group of codeinone was responsible for its antitumor cytotoxicity. The cytotoxic activity of codeinone was significantly reduced by N-acetylcysteine, but not affected by FeCl3, CuCl2, CoCl2, sodium ascorbate or catalase. Neither codeinone nor morphine inhibited P-glycoprotein-mediated rhodamine-123 efflux in multidrug resistant mouse T lymphoma L5178 transfected with human MDR 1 gene. These data suggest that codeinone induces cytotoxicity in oral tumor cell lines, possibly by a Michael-like addition of a protein SH or of an amino group to the bouble bond of codeinone.

Postmortem diffusion of drugs from the bladder into femoral venous blood

We describe significantly elevated drug concentrations in the femoral venous blood due probably to postmortem diffusion from the bladder. A 16-year-old deceased male was found in a shallow ditch in winter. The estimated postmortem interval was 9 days and putrefaction was not advanced. The cardiac chambers contained fluid and coagulated blood and a small amount of buffy coat clots. Diffused hemorrhages were found in the gastric mucosa. The bladder contained approximately 600 ml of clear urine. Gas chromatographic-mass spectrometric analysis of the urine disclosed allylisopropylacetylurea (a fatty acid ureide sedative), diphenhydramine, chlorpheniramine and dihydrocodeine. The cause of death was considered to be drowning due to a drug overdose and cold exposure. The concentrations of diphenhydramine, free dihydrocodeine and total dihydrocodeine in the femoral venous blood (1.89, 3.27 and 3.30 microg/ml, respectively) were much higher than those in blood from the right cardiac chambers (0.294, 0.237 and 0.240 microg/ml, respectively). Urine concentrations of diphenhydramine, free dihydrocodeine and total dihydrocodeine were 22.6, 37.3 and 43.1 microg/ml, respectively. The stomach contained negligible amounts of diphenhydramine, free dihydrocodeine and total dihydrocodeine (0.029, 0.018 and 0.024 mg, respectively); concentrations of these drugs in the femoral muscle were 0.270, 0.246 and 0.314 microg/g, respectively. These results indicate that postmortem diffusion of diphenhydramine and dihydrocodeine from the bladder resulted in the elevated concentrations of these drugs in the femoral venous blood. Not only high urinary drug concentrations but also a large volume of urine in the bladder might accelerate the postmortem diffusion.

Acetylcodeine, an impurity of illicitly manufactured heroin, elicits convulsions, antinociception, and locomotor stimulation in mice

Acetylcodeine is one of the major impurities present in illicitly manufactured heroin (diacetylmorphine). Data on its pharmacology and toxicology are limited and its ability to alter the toxic effects of diacetylmorphine is not known. The first objective of the present study was to compare the acute pharmacological and toxicological effects of acetylcodeine to those of codeine and diacetylmorphine in mice by assessing nociception in the tail-flick test, locomotor stimulation, and convulsive behavior. The second goal of this study was to determine whether acetylcodeine would alter the convulsant effects of diacetylmorphine. The antinociceptive potencies of acetylcodeine and codeine were similar, as reflected by their ED50 (95% confidence limits) values of 35 (29-44) and 51 (40-65) micromol/kg, respectively. Acetylcodeine was somewhat less potent than codeine in stimulating locomotor behavior, with ED50 values of 28 (22-37) and 12 (6-24) micromol/kg, respectively. Diacetylmorphine was considerably more potent than the other two drugs, producing antinociception and locomotor stimulation at ED50 values of 2.4 (1.4-4.1) and 0.65 (0.36-1.2) micromol/kg, respectively. On the other hand, the convulsant effects of acetylcodeine (ED50=138 (121-157) micromol/kg) and diacetylmorphine (ED50=115 (81-163) micromol/kg) were similar in potency and both were more potent than codeine (ED50=231 (188-283) micromol/kg). Finally, a subthreshold dose of acetylcodeine (72 micromol/kg) decreased the convulsant ED50 dose of diacetylmorphine to 40 (32-49). These findings suggest that the convulsant effects of acetylcodeine are more potent than predicted by its effects on locomotor activity and antinociception. The observation that acetylcodeine potentiated the convulsant effects of diacetylmorphine suggests a mechanism for some of the heroin-related deaths reported in human addicts.

The role of dihydrocodeine in causing death among drug users in the west of Scotland

There has been a wealth of information relating to the role of methadone in fatalities over the past decade. However, a dearth exists in the literature of deaths involving dihydrocodeine, a substitute that is being increasingly prescribed by general practitioners for drug harm reduction purposes. Over the past five years in the Strathclyde region of Scotland there has been an increase in the number of drug related deaths involving dihydrocodeine with the largest increase occurring in the latter two years. This in combination with a general acceptance for this drug as a substitute for methadone amongst general practitioners highlights its potential abuse factor which is addressed in this paper. As the number of methadone deaths in relation to the total number of accidental drug related deaths per annum decrease, those related to dihydrocodeine are shown to be increasing.

Novel dynamic polymer coating for capillary electrophoresis in nonaqueous methanolic background electrolytes

Coated capillaries can be advantageous in many capillary electrophoretic applications where nonaqueous background electrolytes are used. In the present work, a new dynamic polymer coating (poly(glycidylmethacrylate-co-N-vinylpyrrolidone)) for methanol-based background electrolytes is introduced. The magnitude and stability of electroosmotic flow was investigated with coated capillaries at pH* values of 3, 7.8, and 10.4 in methanol. At pH* 7.8 and 10.4 the electroosmotic flow was negligible and repeatable. On the other hand, at pH* 3 a weak, unstable electroosmotic flow was observed, due to a change in the conformation of the polymer under acidic conditions. The dynamically coated capillaries were successfully applied to the separations of cationic drugs, phenols, and benzoic acids. The synthesis and characterization of the polymer are described in detail.

Detection of non-prescription heroin markers in urine with liquid chromatography-atmospheric pressure chemical ionization mass spectrometry

The planned introduction of a prescription heroin program in Germany created a need for differentiation between non-prescription and prescribed diamorphine use. The following substances were chosen as markers of non-prescription heroin: acetylcodeine (AC); its metabolites codeine (C) and codeine 6-glucuronide (C6G); papaverine (P); and noscapine (N). Typical heroin markers diamorphine (DAM) and its metabolites monoacetylmorphine (MAM) and morphine (M) were also determined. The drugs were extracted from urine samples with solid-phase extraction (C18) using standard 200-mg columns and 96-well microplates (100 mg). The extracts were examined with liquid chromatography-atmospheric pressure chemical ionization mass spectrometry (positive ionization) in two isocratic systems. Selected ion monitoring procedures were applied for protonated molecular masses and characteristic fragments of drugs involved. The limits of detection were in the range of 0.5-1 ng/mL urine. The occurrence of selected heroin markers was investigated in 25 urine samples collected from heroin abusers (road traffic offenders and overdosed patients). C6G was found in all samples, C in 24 samples, N in 22 samples, MAM in 16 samples, P in 14 samples, DAM in 12 samples, and AC in 4 samples. The appearance of these compounds in urine reflects their pharmacokinetic properties and the composition of non-prescription heroin.

Randomized placebo controlled trial of lofexidine hydrochloride for chronic pelvic pain in women

BACKGROUND

We hypothesised that the orally-active alpha(2)-adrenoceptor agonist lofexidine hydrochloride would ameliorate chronic pelvic pain in women.

METHODS

A randomized placebo-controlled parallel group trial was undertaken in the University Hospital Gynaecology Clinic. Women with pelvic pain of at least 6 months duration were eligible, and were randomized using a sealed envelope system to receive up to 600 mg lofexidine hydrochloride twice daily over 8 weeks or placebo. Outcome measures were summary and daily diary visual analog scales for pain (VAS) and a 5 point self rating scale.

RESULTS

9/19 women randomized to lofexidine completed the study compared to 14/20 of those randomized to placebo. Intention-to-treat analysis showed that 4/19 in the lofexidine group achieved 50% or greater reduction in VAS compared with 8/20 in the placebo group (OR 2.5, 95% CI 0.6--10.3). Summary and diary VAS were closely correlated.

CONCLUSIONS

Within the limits of a small study with power to detect only a substantial effect, we conclude that lofexidine hydrochloride is not effective for the treatment of chronic pelvic pain.

Saliva testing after single and chronic administration of dihydrocodeine

In the present study, concentrations of dihydrocodeine and its metabolites in saliva and serum were compared after single low-dose and chronic high-dosage administration of the drug. In the first investigation, blood and saliva were collected periodically from six subjects after oral administration of 60 mg dihydrocodeine. In the second study, 20 subjects on oral dihydrocodeine maintenance provided single samples of blood and saliva simultaneously. Serum protein binding of salivary analytes and their recovery from the adsorbing material of the collection device as well as pH values of saliva samples were determined. The fluids were analyzed for dihydrocodeine and the major metabolites by high-performance liquid chromatography. In the single dose study dihydrocodeine was the only analyte found in saliva for up to 12-24 h post-dose. The half-life of dihydrocodeine in saliva was about twice that found in blood. The ratios of saliva/serum concentrations ranged from 1.2 to 17.0. After chronic high-dosage use, dihydrocodeine was the main salivary analyte and N-nordihydrocodeine was present in a few samples. Saliva/serum concentration ratios of dihydrocodeine were strongly dependent on the pH value of saliva and, to a lesser extent, on serum-protein binding. The saliva/serum ratios were more similar after chronic administration. The data suggest a passive diffusion process as the underlying mechanism for the transport of dihydrocodeine into saliva. After both single and chronic use, the presence of the drug in saliva can be used as evidence of recent substance administration.

Contribution of dihydrocodeine and dihydromorphine to analgesia following dihydrocodeine administration in man: a PK-PD modelling analysis

AIMS

It is not clear whether the analgesic effect following dihydrocodeine (DHC) administration is due to either DHC itself or its metabolite, dihydromorphine (DHM). We examined the relative contribution of DHC and DHM to analgesia following DHC administration in a group of healthy volunteers using a PK-PD link modelling approach.

METHODS

A single oral dose of DHC (90 mg) was administered to 10 healthy volunteers in a randomised, double-blind, placebo-controlled study. A computerized cold pressor test (CPT) was used to measure analgesia. On each study day, the volunteers performed the CPT before study medication and at 1.25, 2.75, 4.25 and 5.75 h postdose. Blood samples were taken at 0.25 h (predose) and then at half hourly intervals for 5.75 h postdose. PK-PD link modelling was used to describe the relationships between DHC, DHM and analgesic effect.

RESULTS

Mean pain AUCs following DHC administration were significantly different to those following placebo administration (P = 0.001). Mean pain AUC changes were 91 score x s(-1) for DHC and -17 score x s(-1) for placebo (95% CI = +/- 36.5 for both treatments). The assumption of a simple linear relationship between DHC concentration and effect provided a significantly better fit than the model containing DHM as the active moiety (AIC = 4.431 vs 4.668, respectively). The more complex models did not improve the likelihood of model fits significantly.

CONCLUSIONS

The findings suggest that the analgesic effect following DHC ingestion is mainly attributed to the parent drug rather than its DHM metabolite. It can thus be inferred that polymorphic differences in DHC metabolism to DHM have little or no effect on the analgesic affect.

Evaluation of urinary dihydrocodeine excretion in human by gas chromatography-mass spectrometry

Urinary metabolic pattern after the therapeutic peroral dose of dihydrocodeine tartrate to six human volunteers has been explored. Using the GC-MS analytical method, we have found that the major part of the dose administered is eliminated via urine within the first 24 h. However, the analytical monitoring of dihydrocodeine and its metabolites in urine was still possible 72 h after the dose was administered. The dihydrocodeine equivalent amounts excreted in urine in 72 h ranged between 32 and 108% of the dose, on average 62% in all individuals. The major metabolite excreted into urine was a 6-conjugate of dihydrocodeine, then in a lesser amount a 6-conjugate of nordihydrocodeine (both conjugated to approximately 65%). The O-demethylated metabolite dihydromorphine was of a minor amount and was 3,6-conjugated in 85%. Traces of nordihydromorphine and hydrocodone were confirmed as other metabolites of dihydrocodeine in our study. This information can be useful in interpretation of toxicological findings in forensic practice.

GC-MS determination of heroin metabolites in meconium: evaluation of four solid-phase extraction cartridges

A procedure for extraction of heroin and metabolites for gas chromatography-mass spectrometry (GC-MS) analysis of meconium specimens that would allow detection of these analytes at low levels was needed. Solid-phase extraction (SPE) cartridges were therefore evaluated for their effectiveness in sample preparation. Four different types of commercially available extraction cartridges were used. Heroin, 6-monoacetylmorphine (6-MAM), morphine, and codeine were extracted from meconium samples using these SPE cartridges and then simultaneously analyzed using GC-MS. In each case, the extraction efficiency, linearity range, limit of detection (LOD), limit of quantitation (LOQ), between-run precision, and within-run precision were determined. Although satisfactory results were obtained with the four different types of SPE cartridges, best overall performance was observed using Clean Screen columns following the procedures outlined here. LODs as low as 20 ng/g for codeine, 10 ng/g for morphine, and 2.5 ng/g for 6-MAM were obtained, and LOQs as low as 20 ng/g for codeine, 10 ng/g for morphine, and 5 ng/g for 6-MAM were obtained. In all cases linearities were observed (r = > 0.99) for codeine, morphine, and 6-MAM over a wide concentration range (100-2000, 100-2000, and 5-100, respectively). At 50 ng/g codeine and morphine and 10 ng/g 6-MAM, the precision of analysis using these cartridges showed coefficients of variation ranging from 4.75% to 15.5%.

Myocardial Infarction associated with methadone and/or dihydrocodeine

Chest pain and myocardial infarction occurring in young people with angiographically normal coronary arteries is well documented. Opiates have a cardioprotective effect and are used in acute heart attacks. We described a 22-year-old opioid addicted male patient who suffered a myocardial infarction following the consumption of methadone and dihydrocodeine.

Acetylcodeine as a marker of illicit heroin in human hair: method validation and results of a pilot study

Acetylcodeine (AC), which is an impurity of illicit heroin synthesis, was suggested as a marker of heroin abuse. A procedure for simultaneous quantitation of 6-monoacetylmorphine (6-MAM), which is the major metabolite of heroin, morphine, codeine, and AC in hair was developed. Fifty-milligram hair samples were incubated in 0.01 M HCl overnight at 60 degrees C. The resulting hydrolyzed solutions were extracted by an automated solid-phase extraction procedure and drugs were analyzed by gas chromatography-mass spectrometry in selected ion monitoring mode (SIM). This required prior derivatization with propionic anhydride. Different validation parameters, such as linearity, intra-assay accuracy, extraction recoveries, and limit of quantitation, were described. Seventy-three hair samples from heroin abusers and 43 hair samples from subjects who had completed a heroin-maintenance program were analyzed. AC was detected in 92% of the first sample group and in only 12% of the second sample group. In the two groups, about 98% of AC-positive samples were found. These results prove that AC can be considered as a suitable marker of illicit heroin use, along with 6-MAM detection.

Treatment of severe pain from osteoarthritis with slow-release tramadol or dihydrocodeine in combination with NSAID's: a randomised study comparing analgesia, antinociception and gastrointestinal effects

Opioids are increasingly used in the treatment of chronic non-malignant pain. The aim of this open-label, randomised, parallel group study was to compare analgesia and side-effects of two commonly used opioid analgesics, tramadol and dihydrocodeine, in long-acting formulations in 60 osteoarthritis patients with strong pain despite NSAID's. Dose titration based on effect was performed with the respective immediate release solutions given additionally to tramadol 100 mg bid and dihydrocodeine 60 mg bid during the first 4 days of the 1 month treatment. Electrical sensation and pain thresholds over the osteoarthritic joint and at a distant location and gastrointestinal transit times were performed before and during treatment. Thirty patients with pain controlled by NSAID's alone formed the comparator group. Pain intensities at rest and during movement decreased highly significantly with tramadol and dihydrocodeine from median pre-treatment verbal ratings of over 3 (0=none, 4=unbearable) to 1 and below from the second treatment day onwards (ANOVA P<0.0001). Pain at rest was significantly lower with tramadol (ANOVA P=0.04), but ratings were similar during movement. Mean (95% CI) daily doses on days 1 and 28 were 209 (198-220) mg and 203 (191-206) mg of tramadol, and 129 (122-136) mg and 130 (121-134) mg of dihydrocodeine, respectively. Minor side-effects were more common with tramadol (P=0.04). Changes in bowel functions and symptoms were minor with both treatments, but the frequency of defaecation was lower and stools were harder with dihydrocodeine. Orocaecal transit time remained unchanged and similar to controls with both analgesics. Colonic transit times only increased significantly during treatment with dihydrocodeine. Sensation and pain thresholds were lower pre-treatment in both groups than in controls and increased during treatment. These antinociceptive effects were more marked in the tramadol group and distant from the osteoarthritic joint. We conclude rapid pain relief was achieved with both long-acting tramadol and dihydrocodeine with NSAID's in strong osteoarthritis pain. Minimal dose titration was required and side-effects were minor. Tramadol interfered less with intestinal function and showed greater antinociceptive action.

Audit of pain management at home following tonsillectomy in children

The pain experienced at home and the burden this places on primary care resources is considerable following tonsillectomy in children. This was audited by postal questionnaire in 52 patients (36 responders). We found a significant proportion of patients experiencing moderately severe to severe pain and a high rate of consultation with general practitioners (50 per cent) for pain-related issues. These findings lead to changes in practice which included the provision of five days discharge medication (paracetamol/ibuprofen in non-asthmatics; paracetamol/dihydrocodeine in asthmatics) and improved written discharge advice. On re-auditing a year later in 100 patients (56 responders), we found reduced rates of consultation with general practitioners (27 per cent). However, the proportion of children experiencing moderately severe to severe pain was not reduced probably because most children were given the recommended analgesia during the first audit. We also found that paracetamol and ibuprofen was superior to paracetamol and dihydrocodeine for analgesia (p <0.05). Suggestions for further improvements are discussed.

Detection of acetylcodeine in urine as an indicator of illicit heroin use: method validation and results of a pilot study

BACKGROUND

Acetylcodeine (AC), an impurity of illicit heroin synthesis, has been suggested as an interesting biomarker of illicit heroin use.

METHODS

Procedures were developed for quantification of (a) morphine, 6-monoacetylmorphine (6-AM), and codeine in urine and (b) diacetylmorphine and AC in urine. Solid-phase extraction of the analytes was performed, and the extracted analytes were analyzed by selected-ion monitoring with gas chromatography-mass spectrometry. This procedure required prior derivatization with propionic anhydride.

RESULTS

Different validation parameters were determined, such as linearity, reproducibility, extraction recoveries, and cutoffs. Seventy-one urine specimens of illicit heroin abusers and 44 urine specimens of subjects in a heroin maintenance program were analyzed. AC was detected in 85.9% of the samples of the first group but not in any of the samples from subjects taking medical heroin. In the two groups, there were 94.4% and 84.1% 6-AM positive urine specimens, respectively. Detection times were determined for AC and codeine by parallel administration of heroin containing various percentages of AC to four voluntary patients in a heroin maintenance program. The measured detection times were 8 and 23 h for AC and codeine, respectively.

CONCLUSIONS

These results indicate that, together with detection of 6-AM in urine, AC is a suitable marker of illicit heroin use.

Dose-related effects of controlled release dihydrocodeine on oro-cecal transit and pupillary light reflex. A study in human volunteers

It is well accepted that long-term administration of opioids results in a dose-related constipation. No data so far have demonstrated conclusively whether such constipation is also seen after intake of a controlled release formulation. It was therefore of interest to evaluate whether increasing doses of a controlled release formulation of dihydrocodeine (DHC, CAS 125-28-0) after oral administration also induces a dose-related increase in constipation. Additionally, it was of interest to study whether such a peripheral opioid-related side effect is also seen in another, central receptor-mediated effect, the constriction of the pupil, at clinically relevant doses. Twelve volunteers were given controlled release DHC (60 and 120 mg, respectively) or placebo orally within a randomized, double-blind cross-over study. In order to determine the degree of constipation, oro-cecal transit time was measured using the H2-exhalation test. Additionally, in order to evaluate a centrally mediated effect, the response of the pupil to light was quantified using the pupillary light reflex technique. Both, peripherally and centrally mediated effects were compared to placebo. DHC at both dosages induced a significant (p < 0.01) prolongation of oro-cecal transit time when compared to placebo. However, prolongation of oro-cecal transit was not significantly longer when comparing the lower (60 mg) with the higher dose (120 mg). DHC also induced a significant (p < 0.005) depression of the pupillary light reflex from 53.9 mm (control) to 8.3 and 7.4 mm, respectively. Similar to intestinal transit, the pupillary light reflex was not significantly different among the two doses of DHC. Also, both dosages induced a similar amount of side effects. Tiredness and dry mouth were reported in 80% after both doses while vertigo was reported in 5% and 1% complained of headache. None of the volunteers reported nausea or emesis. It is concluded that opioid receptor sites, which are located in the plexus myentericus of the intestinal wall, are responsible for the delay in propulsion. Because of the controlled release of a fixed amount of DHC over time there is constant binding of the ligand followed by a constant conformational change of peripheral and central receptor sites. Thus constant release induces no dose-related increase in oro-cecal transit and inhibition of the pupillary light reflex.

Analysis of codeine, dihydrocodeine and their glucuronides in human urine by electrokinetic capillary immunoassays and capillary electrophoresis-ion trap mass spectrometry

Screening for and confirmation of illicit, abused and banned drugs in human urine is a timely topic in which capillary separation techniques play a key role. Capillary electrophoresis (CE) represents the newest technology employed in this field of analysis. Two rapid competitive binding, electrokinetic capillary-based immunoassays are shown to be capable of recognizing the presence, but not the identity, of urinary opioids, namely codeine (COD), codeine-6-glucuronide, dihydrocodeine (DHC), dihydrocodeine-6-glucuronide, morphine (MOR), morphine-3-glucuronide and ethylmorphine (EMOR). In these approaches, aliquots of urine and immunoreagents of a commercial, broadly cross-reacting fluorescence polarization immunoassay for opiates were combined and analyzed by capillary zone electrophoresis or micellar electrokinetic capillary chromatography with laser induced fluorescence detection. With the fluorescent tracer solution employed, the former method is shown to provide simple electropherograms which are characterized by an opioid concentration dependent magnitude of the free tracer peak. In presence of dodecyl sulfate micelles, however, two tracer peaks with equal opioid concentration sensitivity are monitored. These data suggest the presence of two fluorescent tracers which react competitively with the urinary opioids for the binding sites of the antibody. Assay sensitivities for COD and MOR are comparable (10 ng/ml), whereas those for DHC and EMOR are about four-fold lower. Furthermore, glucuronides are shown to react like the corresponding free opioids. Analysis of urines that were collected after administration of 7 mg COD and 25 mg DHC tested positively in both assay formats. The presence of the free and conjugated codeinoids in these urines and their identification was accomplished by capillary electrophoresis-ion trap mass spectrometry (CE-MS). This confirmatory assay is based upon solid-phase extraction using a mixed-mode polymer cartridge followed by CE hyphenated to the LCQ mass spectrometer with electrospray ionization in the positive ion mode. With this technology, MS2 is employed for proper identification of COD (m/z 300.4) and DHC (m/z 302.4) whereas MS3 provides unambiguous identification of the glucuronides of COD (m/z 476.5) and DHC (m/z 478.5) via their fragmentation to COD and DHC, respectively. MSn (n > or = 2) is shown to be capable of properly identifying the urinary codeinoids on the 100-200 ng/ml concentration level.

Micellar electrokinetic and high-performance liquid chromatographic determination of potential manufacturing impurities in pholcodine

Quantitative high-performance liquid chromatographic (HPLC) and micellar electrokinetic chromatographic (MEKC) methods have been developed for the determination of four structurally related potential manufacturing impurities, including morphine, of the opiate derivative pholcodine. Pholcodine and the four impurities were separated by MEKC in less than 14 min using a 70 cm x 75 microm I.D. uncoated fused-silica capillary (25 kV at 30 degrees C) and a running buffer consisting of 10% acetonitrile (v/v) in 20 mM borate-phosphate buffer pH 8.0 containing 40 mM sodium dodecyl sulphate (SDS). The MEKC method was compared to a HPLC method using a 5 microm Luna phenyl-hexyl column (150 x 4.6 mm I.D.) eluted with a mobile phase consisting of a mixture of 10% (v/v) acetonitrile, 7% (v/v) tetrahydrofuran in 20 mM phosphate buffer pH 8.0. Both methods were fully validated and a comparison was made regarding selectivity, linearity, precision, robustness and limits of detection and quantitation. The presence of the impurities in different samples of pholcodine drug substance was investigated using both methods.

Characteristic glucuronidation pattern of physiologic concentration of morphine in rat brain

Formation of conjugated metabolites from morphine at a very low level in brain was studied in vitro in rats. Incubation of a low concentration of 3H-morphine with brain homogenate followed by two successive high-performance liquid chromatographic analyses showed that endogenous morphine is converted by brain enzymes to its 3- and 6-glucuronides (M-3-G and M-6-G), and codeine glucuronide (Cod-G). However, the formation of morphine-6-sulfate was likely to be low if it was produced at all. All of the cerebral hemisphere, brain stem and cerebellum were capable of producing M-3-G, M-6-G and Cod-G, although there were differences in selectivity. The capacity of the brain for glucuronide formation was far less than that of the liver, but UDP-glucuronosyltransferase in brain was much more selective in forming M-6-G and Cod-G than liver enzymes.

Dihydrocodeine: a useful tool in the detoxification of methadone-maintained patients

We investigated the merit of dihydrocodeine tartrate for withdrawal in detoxifying 20 methadone-maintained patients presenting for treatment at the Leeds Addiction Unit (LAU). Thirteen patients (65%) successfully completed methadone detoxification and were abstinent from both methadone and opiate-type drugs at the end of the 2-week program. On completion, three patients began treatment with Naltrexone and another was abstinent at a follow-up appointment, 1 week later. A further patient relapsed back to heroin use but remained in contact with the LAU. The remaining six patients dropped out of the 2-week detoxification program between days 3 and 11 of the dihydrocodeine cross-over period. We believe dihydrocodeine may have advantages in detoxifying methadone-maintained patients.

In vitro interaction of codeine and diclofenac

There is very limited knowledge about possible pharmacokinetic interactions between opioid analgesics and nonsteroidal antiinflammatory drugs (NSAIDs), which are commonly used in combination for the treatment of chronic pain. The major metabolic pathway of the weak opioid codeine is glucuronidation to codeine-6-glucuronide. Therefore we investigated the influence of the NSAID diclofenac on the formation of codeine-6-glucuronide in vitro, using human liver tissue homogenate. The formation of codeine-6-glucuronide exhibited single enzyme Michaelis-Menten kinetics with an average V(max) of 93.6 +/- 35.3 pmol/mg/min. A noncompetitive inhibition of codeine-6-glucuronidation by diclofenac was observed with an average K(i) of 7.9 microM. These in vitro findings suggest that a pharmacokinetic interaction occurs in vivo, which has to be confirmed by an interaction study in human subjects. It can be speculated that in case of inhibition of glucuronidation, the amount of codeine available for other pathways especially O-demethylation to morphine is increased, resulting in higher morphine serum levels and therefore higher analgesic efficacy.

Modified liquid junction interface for nonaqueous capillary electrophoresis-mass spectrometry

Electrospray ionization (ESI) is the most widely used ionization method in on-line coupling of capillary electrophoresis-mass spectrometry (CE-MS). The conventional coaxial sheath flow electrospray interface is currently being replaced by the more sensitive nanoelectrospray technique. The usual limitation of nanoelectrospray CE-MS interface has been its short lifetime caused by deterioration of the metal coating on the CE capillary terminus. This article describes an easy way to construct a more durable and sensitive nanospray interface for nonaqueous CE-MS. In this approach a very thin glass spray capillary (ca. 30 microm outer diameter) is partly inserted inside the CE capillary, the junction being surrounded by the electrolyte medium, which is in contact with the platinum electrode. The interface was tested with five pharmaceuticals: methadone, pentazocine, levorphanol, dihydrocodeine, and morphine. Detection limits ranged from 12 to 540 fmol. Separation efficiency and reproducibility were also studied. The CE current was found to be stable and the migration times were highly reproducible. All the CE separations were carried out in a nonaqueous background electrolyte solution.

Postoperative analgesia and vomiting, with special reference to day-case surgery: a systematic review

BACKGROUND

Day-case surgery is of great value to patients and the health service. It enables many more patients to be treated properly, and faster than before. Newer, less invasive, operative techniques will allow many more procedures to be carried out. There are many elements to successful day-case surgery. Two key components are the effectiveness of the control of pain after the operation, and the effectiveness of measures to minimise postoperative nausea and vomiting.

OBJECTIVES

To enable those caring for patients undergoing day-case surgery to make the best choices for their patients and the health service, this review sought the highest quality evidence on: (1) the effectiveness of the control of pain after an operation; (2) the effectiveness of measures to minimise postoperative nausea and vomiting.

METHODS

Full details of the search strategy are presented in the report. RESULTS - ANALGESIA: The systematic reviews of the literature explored whether different interventions work and, if they do work, how well they work. A number of conclusions can be drawn. RESULTS-ANALGESIA, INEFFECTIVE INTERVENTIONS: There is good evidence that some interventions are ineffective. They include: (1) transcutaneous electrical nerve stimulation in acute postoperative pain; (2) the use of local injections of opioids at sites other than the knee joint; (3) the use of dihydrocodeine, 30 mg, in acute postoperative pain (it is no better than placebo). RESULTS-ANALGESIA, INTERVENTIONS OF DOUBTFUL VALUE: Some interventions may be effective but the size of the effect or the complication of undertaking them confers no measurable benefit over conventional methods. Such interventions include: (1) injecting morphine into the knee joint after surgery: there is a small analgesic benefit which may last for up to 24 hours but there is no clear evidence that the size of the benefit is of any clinical value; (2) manoeuvres to try and anticipate pain by using pre-emptive analgesia; these are no more effective than standard methods; (3) administering non-steroidal anti-inflammatory drugs (NSAIDs) by injection or per rectum in patients who can swallow; this appears to be no more effective than giving NSAIDs by mouth and, indeed, may do more harm than good; (4) administering codeine in single doses; this has poor analgesic efficacy. RESULTS-ANALGESIA, INTERVENTIONS OF PROVEN VALUE: These include a number of oral analgesics including (at standard doses): (1) dextropropoxyphene; (2) tramadol; (3) paracetamol; (4) ibuprofen; (5) diclofenac. Diclofenac and ibuprofen at standard doses give analgesia equivalent to that obtained with 10 mg of intramuscular morphine. Each will provide at least 50% pain relief from a single oral dose in patients with moderate or severe postoperative pain. Paracetamol and codeine combinations also appear to be highly effective, although there is little information on the standard doses used in the UK. The relative effectiveness of these analgesics is compared in an effectiveness 'ladder' which can inform prescribers making choices for individual patients, or planning day-case surgery. Dose-response relationships show that higher doses of ibuprofen may be particularly effective. Topical NSAIDs (applied to the skin) are effective in minor injuries and chronic pain but there is no obvious role for them in day-case surgery. RESULTS-POSTOPERATIVE NAUSEA AND VOMITING: The proportion of patients who may feel nauseated or vomit after surgery is very variable, despite similar operations and anaesthetic techniques. Systematic review can still lead to clear estimations of effectiveness of interventions. Whichever anti-emetic is used, the choice is often between prophylactic use (trying to prevent anyone vomiting) and treating those people who do feel nauseated or who may vomit. Systematic reviews of a number of different anti-emetics show clearly that none of the anti-emetics is sufficiently effective to be used for prophylaxis. (ABSTRACT TRUNCATE

The [4+2]] addition of singlet oxygen to thebaine: new access to highly functionalized morphine derivatives via opioid endoperoxides

The photooxidation of thebaine (3) with a sun lamp affords two main products: hydrodibenzofuran 10 (major) and benzofuran 11 (minor). The latter compound becomes predominant if a Hg lamp is used instead of a sun lamp. The formation of 10 proceeds via an endoperoxide intermediate that undergoes oxidation at the nitrogen atom. Protection of the nitrogen either by protonation or quaternization prevents its oxidation and thus the photooxidation of 3 in acid media constitutes a one-pot procedure for the preparation of 14-hydroxycodeinone 35. Photooxidation of the thebaine ammonium salt 31 allows the isolation in good yields of the corresponding to thebaine endoperoxide 32. The selective protection and reduction of the keto, aldehyde, and olefinic groups of hydrodibenzofuran 10 allowed the preparation of several diol and keto alcohol derivatives. This is the first report on the use of photooxidation to functionalize thebaine at C(6) and C(14) and also the first on the isolation of opioid endoperoxides.

Isolation and identification of three potential impurities of pholcodine bulk drug substance

Three previously unreported manufacturing impurities were isolated from a pholcodine mother liquor using preparative reversed-phase HPLC. The liquor was the residue remaining after recrystallisation of a production batch of pholcodine. The impurities, which are structurally related to pholcodine, were initially detected by thin-layer chromatography (TLC). Their structures were determined after separation by preparative HPLC (Econo-Prep 5 microm C18 column, 30 cm x 21.2 mm i.d.). Structure elucidation was carried out using nuclear magnetic resonance (NMR) spectroscopy, mass spectroscopy (MS) and ultra violet (UV) spectroscopy. The impurities were identified as alkylated derivatives of pholcodine possessing second 2-morpholinoethyl substituents at various positions.

Codeine analgesia is due to codeine-6-glucuronide, not morphine

Eighty per cent of codeine is conjugated with glucuronic acid to codeine-6-glucuronide. Only 5% of the dose is O-demethylated to morphine, which in turn is immediately glucuronidated at the 3- and 6-position and excreted renally. Based on the structural requirement of the opiate molecule for interaction with the mu-receptor to result in analgesia, codeine-6-glucuronide in analogy to morphine-6-glucuronide must be the active constituent of codeine. Poor metabolisers of codeine, those who lack the CYP450 2D6 isoenzyme for the O-demethylation to morphine, experience analgesia from codeine-6-glucuronide. Analgesia of codeine does not depend on the formation of morphine and the metaboliser phenotype.

On the assessment of drug metabolism by assays of codeine and its main metabolites

Codeine and its main metabolites appear to have advantages for assessing drug metabolic phenotypes. The authors have further developed a high-performance liquid chromatography (HPLC) method for the quantification of codeine and six of its metabolites in urine. Quantification was performed by electrochemical detection for morphine, normorphine, morphine-6-glucuronide, and the internal standard 4-O-methyldopamine; and by ultraviolet detection for codeine, norcodeine, and morphine-3-glucuronide. The method had a detection limit of 2 nmol/L(-1) for morphine and normorphine, 4 nmol/L(-1) for morphine-6-glucuronide, 3 nmol/L for the internal standard, 20 nmol/L(-1) for morphine-3-glucuronide, and 60 nmol/L(-1) for codeine and norcodeine. The coefficients of variations were <9% for intraday and <10% for interday analyses. The recovery of codeine and its metabolites ranged from 55% (for morphine-3-glucuronide) to 90% (for codeine, norcodeine, morphine, and morphine-6-glucuronide). Eleven healthy volunteers were phenotyped for CYP2D6 using codeine as well as debrisoquine and dextromethorphan. Ten subjects were extensive metabolizers (EM) and one a poor metabolizer (PM) of codeine, debrisoquine, and dextromethorphan. Significant correlations between the metabolic ratios (MRs) of the different probe drugs were obtained (r2 > 0.95, p < 0.001). This HPLC method is simple, sensitive, accurate, and reproducible for assessing the CYP2D6 phenotype.

Morphine-related metabolites differentially activate adenylyl cyclase isozymes after acute and chronic administration

Morphine-3- and morphine-6-glucuronide are morphine's major metabolites. As morphine-6-glucuronide produces stronger analgesia than morphine, we investigated the effects of acute and chronic morphine glucuronides on adenylyl cyclase (AC) activity. Using COS-7 cells cotransfected with representatives of the nine cloned AC isozymes, we show that AC-I and V are inhibited by acute morphine and morphine-6-glucuronide, and undergo superactivation upon chronic exposure, while AC-II is stimulated by acute and inhibited by chronic treatment. Morphine-3-glucuronide had no effect. The weak opiate agonists codeine and dihydrocodeine are also addictive. These opiates, in contrast to their 3-O-demethylated metabolites morphine and dihydromorphine (formed by cytochrome P450 2D6), demonstrated neither acute inhibition nor chronic-induced superactivation. These results suggest that metabolites of morphine (morphine-6-glucuronide) and codeine/dihydrocodeine (morphine/dihydromorphine) may contribute to the development of opiate addiction.

GCD quantitation of opiates as propionyl derivatives in blood

We describe a method using a gas chromatograph with electron ionization detection (GCD) for the simultaneous determination of morphine, codeine, 6-monoacetylmorphine, ethylmorphine, and dihydrocodeine in blood. The method employs propionic anhydride in the presence of triethylamine to propionylate free hydroxyl groups of the opiates in blood. The quantitation is achieved by using GCD with selected ion monitoring of the two most characteristic ions for each analyte. The quantitation limit was 0.01 mg/L and the linearity was 0.01-10 mg/L for dihydrocodeine, ethylmorphine, and 6-monoacetylmorphine. For the other investigated opiates, the quantitation limit was 0.025 mg/L and linearity was 0.025-10 mg/L. The intraday relative standard deviation (RSD) varied from 7.2 to 10% at the 0.5 mg/L level, and the day-to-day RSDs varied from 7.5 to 11% at the 0.85 mg/L level.

Single dose dihydrocodeine for acute postoperative pain

BACKGROUND

Dihydrocodeine is a synthetic opioid analgesic developed in the early 1900s. Its structure and pharmacokinetics are similar to that of codeine and it is used for the treatment of postoperative pain or as an antitussive. It is becoming increasingly important to assess the relative efficacy and harm caused by different treatments. Relative efficacy can be determined when an analgesic is compared with control under similar clinical circumstances.

OBJECTIVES

To quantitatively assess the analgesic efficacy and adverse effects of single-dose dihydrocodeine compared with placebo in randomised trials in moderate to severe postoperative pain.

SEARCH STRATEGY

Published reports were identified from a variety of electronic databases including Medline, Biological Abstracts, Embase, the Cochrane Library and the Oxford Pain Relief Database. Additional studies were identified from the reference lists of retrieved reports.

SELECTION CRITERIA

The following inclusion criteria were used: full journal publication, clinical trial, random allocation of patients to treatment groups, double blind design, adult patients, pain of moderate to severe intensity at baseline, postoperative administration of study drugs, treatment arms which included dihydrocodeine and placebo and either oral or injected (intramuscular or intravenous) administration of study drugs.

DATA COLLECTION AND ANALYSIS

Data collection and analysis: Summed pain intensity and pain relief data over 4-6 hours were extracted and converted into dichotomous information to yield the number of patients obtaining at least 50% pain relief. This was used to calculate relative benefit and number-needed-to-treat for one patient to obtain at least 50% pain relief. Single-dose adverse effect data were collected and used to calculate relative risk and number-needed-to-harm.

MAIN RESULTS

Fifty-two reports were identified as possible randomised trials which assessed dihydrocodeine in postoperative pain. Four reports met the inclusion criteria; all assessed oral dihydrocodeine. Three reports (194 patients) compared dihydrocodeine with placebo and one (120 patients) compared dihydrocodeine (30 mg or 60 mg) with ibuprofen 400 mg. For a single dose of dihydrocodeine 30 mg in moderate to severe postoperative pain the NNT for at least 50% pain relief was 8.1 (95% confidence interval 4.1 to 540) when compared with placebo over a period of 4-6 hours. Pooled data showed significantly more patients to have reported adverse effects with dihydrocodeine 30 mg than with placebo. When compared to ibuprofen 400 mg both dihydrocodeine 30 mg and 60 mg were significantly inferior.

REVIEWER'S CONCLUSIONS

A single 30 mg dose of dihydrocodeine is not sufficient to provide adequate pain relief in postoperative pain. Statistical superiority of ibuprofen 400 mg over dihydrocodeine (30 mg or 60 mg) was shown.

Oscillatory breathing patterns during wakefulness in patients with chronic heart failure: clinical implications and role of augmented peripheral chemosensitivity

BACKGROUND

Oscillatory breathing patterns characterized by rises and falls in ventilation with apnea (Cheyne-Stokes respiration [CSR]) or without apnea (periodic breathing [PB]) commonly occur during the daytime in chronic heart failure (CHF). We have prospectively characterized patients with cyclical breathing in terms of clinical characteristics, indices of autonomic control, prognosis, and the role of peripheral chemosensitivity.

METHODS AND RESULTS

To determine cyclical breathing pattern, power spectral analysis was applied to 30-minute recordings of respiration in 74 stable CHF patients. Analyses of heart rate variability and baroreflex sensitivity were used to assess autonomic balance. Peripheral chemosensitivity was assessed with the transient hypoxia method. We also determined whether the suppression of peripheral chemoreceptor activity (hyperoxia or dihydrocodeine) would influence the respiratory pattern. Cyclical respiration was found in 49 (66%) patients (22 [30%] CSR, 27 [36%] PB) and was associated with more advanced CHF symptoms, impaired autonomic balance, and increased chemosensitivity (0.80 and 0.75 versus 0.34 L. min(-1). %SaO(2)(-1), P<0.001, for CSR and PB versus normal breathing, respectively). Transient hyperoxia abolished oscillatory breathing in 7 of 8 patients. Dihydrocodeine administration decreased chemosensitivity by 42% (P=0.05), which correlated with improvement in respiratory pattern. Cyclical breathing predicted poor 2-year survival (relative risk 9.41, P<0.01, by Cox proportional hazards analysis), independent of peak oxygen consumption (P=0.04).

CONCLUSIONS

An oscillatory breathing pattern during the daytime is a marker of impaired autonomic regulation and poor outcome. Augmented activity of peripheral chemoreceptors may be involved in the genesis of this respiratory pattern. Modulation of peripheral chemosensitivity can reduce or abolish abnormal respiratory patterns and may be an option in the management of CHF patients with oscillatory breathing.

Transformations of codeine to important semisynthetic opiate derivatives by Pseudomonas putida m10

A biotransformation mixture which contained codeine and washed cells of Pseudomonas putida M10 gave rise to a number of transformation products that are of clinical importance which included hydrocodone, dihydrocodeine and 14beta-hydroxycodeine. Incubations with the same organism and codeinone gave rise to 14beta-hydroxycodeinone and 14beta-hydroxycodeine. Cell-free extracts and membrane fractions of P. putida M10 were shown to catalyse the 14beta-hydroxylation of codeinone. In addition, the potent analgesic oxycodone was shown to be produced from 14beta-hydroxycodeinone.

Effects of epinastine on the antitussive and rewarding effects of dihydrocodeine in mice

The effects of chlorpheniramine and epinastine on dihydrocodeine were examined in mice. Orally administered dihydrocodeine (3-30 mg/kg) dose-dependently inhibited the number of capsaicin-induced coughs. The dose-dependent antitussive effects of dihydrocodeine were enhanced by each corresponding dose of chlorpheniramine or epinastine delivered at a ratio generally similar to that found in over-the-counter antitussive preparations (dihydrocodeine:histamine H1 antagonist = 3:1). The ED50 value of dihydrocodeine in combination with chlorpheniramine was nearly the same as that for dihydrocodeine in combination with epinastine. On the other hand, while combination treatment with dihydrocodeine (3 mg/kg i.p.) and chlorpheniramine (1 mg/kg s.c.) significantly potentiated place preference, no potentiation was observed with the combination of dihydrocodeine (3 mg/kg i.p.) and epinastine (1 mg/kg s.c.). These results suggest that epinastine may be a useful constituent opioid-containing antitussive preparation that would not enhance the potential for psychological dependence.