The combined use of high-performance liquid chromatography and radioimmunoassay for the bioanalysis of nicomorphine and its metabolites

Towards identifying nicomorphine administration in doping control: synthesis of metabolites

Aim: Nicomorphine is rapidly metabolized mainly to the biologically active 6-nicotinoyl morphine and morphine. In sport, morphine and nicomorphine use is prohibited whereas codeine use is permitted. Accredited laboratories routinely test for morphine hence must be able to distinguish morphine, as a metabolite of a prohibited substance, from that whose use is permitted. Results: Here we show a relatively simple method to synthesize the nicomorphine metabolites, 3-nicotinoyl and 6-nicotinoyl morphine, and indicate how they may be used to identify nicomorphine administration. Conclusion: This approach should help confirm that it is not codeine, an allowable analgesic in sport, that has been administered.

Pharmacokinetics of nicomorphine and its metabolites in man after epidural administration

In ten patients who received an epidural injection of 15 mg of nicomorphine, the compound was relatively slowly released from the epidural space and was found in plasma for approximately 1.5 h. Nicomorphine is relatively slowly metabolized into 6-nicotinoylmorphine and morphine. The rate of release is patient-dependent. The relative AUC values are 15.3% for nicomorphine, 23.9% for 6-nicotinoylmorphine and 60.8% for morphine. The mean clinical effect lasts for 18.2 +/- 10.1 h.

Prodrug behaviour of nicotinoylmorphine esters

Morphine and its nicotinoyl esters, dinicotinoylmorphine (nicomorphine), 6-mononicotinoylmorphine (6-MNM) and 3-mononicotinoylmorphine (3-MNM) were tested in mice for central activity to obtain time-effect profiles of these compounds in rats. Two effects, analgesia with the hot plate test and locomotor stimulation in activity cages were measured and nicomorphine, 6-MNM and 3-MNM were found to have a faster onset of action compared with morphine. The effects of 3-MNM and morphine lasted longer than the effect of nicomorphine and 6-MNM. The prodrug behaviour of 3-MNM and nicomorphine for morphine and 6-MNM, respectively, is discussed.

Importance of analytical methods in pharmacokinetic and drug metabolism studies

Pharmacokinetic and drug metabolism studies first request that good analytical data are available. The various methods that permit unchanged drugs and their metabolites to be separated, identified and quantitatively assayed are briefly reviewed. The present importance of gas chromatography/mass spectrometry is emphasized, as well as the limits of immunological assays. The sensitivity of the analytical assay has a direct impact on the validity of the pharmacokinetic model which is built up from plasma concentration data. The precision and accuracy of the assay is also critical, and it is not always easily estimated. A new significant parameter is the speed of analysis, and the resulting massive production of analytical data. New drugs coming from biotechnology, and new dosage forms, like targeted drugs, will create new analytical problems in the future. They will probably call for the development of new biological or pharmacological assay procedures, in addition to the physicochemical means of analysis.