Capillary and packed column GC determination of propoxyphene and norpropoxyphene in biological specimens: analytical problems and improvements

Screening for drugs of abuse (II): Cannabinoids, lysergic acid diethylamide, buprenorphine, methadone, barbiturates, benzodiazepines and other drugs

Requirements for the provision of an efficient and reliable service for drugs of abuse screening in urine have been summarized in Part I of this review. The requirements included rapid turn-around times, good communications between requesting clinicians and the laboratory, and participation in quality assessment schemes. In addition, the need for checking/confirmation of positive results obtained for preliminary screening methods was stressed. This aspect of the service has assumed even greater importance with widespread use of dip-stick technology and the increasing number of reasons for which drug screening is performed. Many of these additional uses of drug screening have possible serious legal implications, for example, screening school pupils, professional footballers, parents involved in child custody cases, persons applying for renewal of a driving licence after disqualification for a drug-related offence, doctors seeking re-registration after removal for drug abuse, and checking for compliance with terms of probation orders; as well as pre-employment screening and work-place testing. In many cases these requests will be received from a general practitioner or drug clinic with no indication of the reason for which testing has been requested. This also raises the serious problems of a chain of custody, provision of two samples, stability of samples, and secure and lengthy storage of samples in the laboratory-samples may be requested by legal authorities several months after the initial testing. The need for confirmation of positive results is now widely accepted but it may be equally important to confirm unexpected negative results. Failure to detect the presence of maintenance drugs may lead to the patient being discharged from a drug treatment clinic and, if attendance at the clinic is one of the terms of continued employment, to dismissal. It seems likely that increasing abuse of drugs and the efforts of regulatory authorities to control this, will lead to the manufacture of more designer drugs. Production of substituted phenethylamines was facilitated by the drug makers' cook book, 'PIHKAL' (Phenethylamines I Have Known And Loved) by Dr Alexander Shulgin and Ann Shulgin, and production of substituted tryptamines is promised in their next book, TIHKAL. Looking to the future, laboratories will need to ensure that they can detect and quantitate an ever-increasing number of drugs and related substances. The question of confidence in results of drugs of abuse testing raised in 1993 by Watson has assumed even greater importance as a result of attention focused on the OJ Simpson trial in Los Angeles. Toxicological investigations are likely to be challenged more frequently in the future. Even if analyses have been performed by GC-MS, there is a need to establish the level of match between the spectrum of the unknown substance and a library spectrum which is considered acceptable for legal purposes. It will also be essential to ensure that computer libraries contain spectra for all substances likely to be encountered in drugs of abuse screening.

Synthesis of new d-propoxyphene derivatives and the development of a microparticle-based immunoassay for the detection of propoxyphene and norpropoxyphene

The synthesis of [S-(R,S)]-4-[[methyl[2-methyl-3-(1-oxopropoxy)-3, 4-diphenylbutyl]amino]-1-oxobutoxy]-2,5-pyrrolidinedione+ ++ (propoxyphene active ester, 2) is described. This was used as an intermediate to prepare a propoxyphene immunogen, [S-(R,S)]-4-[methyl][2-methyl-3-(1-oxopropoxy)-3,4-diphenylbuty l]-amino]- 1-oxobutyl-Bovine Thyroglobulin (3). This immunogen was then used to generate antibodies which demonstrate good cross-reactivity to d-propoxyphene, d-norpropoxyphene, and other propoxyphene metabolites. In addition, these antibodies were shown to have very low cross-reactivity to methadone, a structurally related compound. The introduction of an aminomethyl benzoate spacer into the propoxyphene active ester (2), followed by the activation of the carboxylic acid, provided for a more stable active ester (5). This stable active ester, together with the antibodies generated from the propoxyphene immunogen, has led to the development of an immunoassay based on the Kinetic Interaction of Microparticles in Solution (KIMS).

Simultaneous determination of dextromoramide, propoxyphene and norpropoxyphene in necropsic whole blood by liquid chromatography

Dextromoramide, propoxyphene and its main metabolite, norpropoxyphene, were determined in blood after solid-liquid extraction by means of an HPLC method using photodiode-array detection. Two cases of fatal overdose resulting from abuse of the two drugs are presented. In case 1 the necropsic whole blood contained dextromoramide at toxic level (194 ng ml-1) and propoxyphene (614 ng ml-1) and norpropoxyphene (1100 ng ml-1) within the therapeutic range; the death could be due to the combined effect of the two analgesics and, perhaps, other associated drugs. In case 2, the necropsic whole blood concentrations of propoxyphene and norpropoxyphene were 4330 and 3800 ng ml-1, respectively, and could be considered as lethal.

Determination of dextropropoxyphene and norpropoxyphene in plasma by high-performance liquid chromatography

A simple and sensitive procedure for the routine assay of the analgesic drug dextropropoxyphene and its main metabolite, norpropoxyphene, in plasma is described. After liquid-liquid extraction from alkalinized plasma and back-extraction into a small volume of an acidic aqueous phase, the aqueous phase was injected into a column packed with 3-microns octadecylsilica particles. Ultraviolet absorbance detection at 210 nm was used. Concentrations down to 2 nM could be determined for both compounds; at this level, the intra-assay coefficient of variation was 5%.

Dextropropoxyphene poisoning: problems with interpretation of analytical data

Difficulties in the estimation and interpretation of dextropropoxyphene and norpropoxyphene analyses have added to the controversy concerning the toxicity of these compounds. Poor performance in external proficiency assessment trials reflects the unsatisfactory state of many dextropropoxyphene and norpropoxyphene analyses in general use. There is substantial overlap between blood concentrations of dextropropoxyphene and norpropoxyphene encountered in chronic therapeutic dose and those associated with acute toxicity. As dextropropoxyphene and norpropoxyphene are often taken in overdose with other drugs, their blood concentrations must be interpreted in the context of careful identification and quantitation of such agents. The present availability of accurate methods for measurement of parent drug and metabolite should now make anecdotal reports unsupported by analytical data entirely superfluous.

Measurement of dextropropoxyphene and nordextropropoxyphene in biological fluids

Detection, identification and measurement of dextropropoxyphene and its principal plasma metabolite, nordextropropoxyphene, can be important in the diagnosis of acute poisoning. A combination of thin-layer chromatography (TLC) and gas-liquid chromatography (GLC) of solvent or solid-phase extracts of urine or gastric contents usually serves to detect these and many other compounds, and an homogeneous enzyme immunoassay (EMIT-DAU) is also available for dextropropoxyphene. Measurement of dextropropoxyphene by GLC is complicated by the instability of this compound under certain conditions. However, a relatively polar stationary phase such as Carbowax 20M together with nitrogen-selective detection can give adequate sensitivity and selectivity for the measurement of the plasma concentrations attained after overdosage. High-performance liquid chromatography (HPLC) has not been widely applied in the assay of dextropropoxyphene and nordextropropoxyphene since these compounds have no pronounced ultraviolet absorption or fluorescence spectra. However, electrochemical oxidation detection can be used with a silica column/non-aqueous ionic eluent system. This gives good selectivity and sensitivity, and can facilitate the measurement of both compounds in plasma specimens after single oral dosage.