High-performance liquid chromatography and preliminary pharmacokinetics of nicomorphine and its metabolites 3-nicotinoyl- and 6-nicotinoylmorphine and morphine

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.

Determination of morphine 3-esters in rabbit plasma by high-performance liquid chromatography with ultraviolet detection

A sensitive high-performance liquid chromatographic (HPLC) method for the quantitation of the morphine 3-esters 1[3-(2, 2-dimethylvaleroyl)-morphine (A), 3-(2-phenylbenzoyl)-morphine (B) and 3-(2,2-diphenylpropionyl)-morphine (C)] in rabbit plasma is described. Sample preparation was based on reversed-phase solid-phase extraction. The compounds were separated on C(18) reversed-phase analytical columns and then determined by ultraviolet detection. The recovery from plasma was 78.7 +/- 7.4%, 69.1 +/- 6.9% and 75 +/- 7.2% (mean +/- SD) for A, B, and C, respectively. The present method enabled the detection limit of 0.2, 0.2 and 0.1 ng and quantification limit of 20, 10 and 10 ng/ml for A, B and C, respectively. The developed method was used for determination of the plasmakinetics of these morphine 3-esters in rabbits.

Pharmacokinetics of epidurally administered nicomorphine with its metabolites and glucuronide conjugates in patients undergoing pulmonary surgery during combined epidural local anaesthetic block and general anaesthesia

After epidural administration of 15 mg 3, 6-dinicotinoylmorphine (nicomorphine) in 10 patients undergoing pulmonary surgery, the parent compound was quickly metabolized into the metabolites 6-mononicotinoylmorphine and morphine. The mean apparent half-lives (+/- SD) of elimination were 10 min (0.165 h +/- 0.053 h) for 3,6-dinicotinoylmorphine and 1.77 h +/- 1.23 h for 6-mononicotinoylmorphine. Morphine is subsequently metabolized into morphine-3-glucuronide and morphine-6-glucuronide. The apparent half-lives of morphine, morphine-3-glucuronide, and morphine-6-glucuronide are similar: 3.63 h +/- 1.63 h, 4.10 h +/- 0.57 h, and 4.20 h +/- 1.64 h respectively. The possible glucuronide conjugate of 6-mononicotinoylmorphine was not detected. The prodrug 3,6-dinicotinoylmorphine was biotransformed into three active compounds: 6-mononicotinoylmorphine, morphine, and morphine-6-glucuronide.

Rectal administration of nicomorphine in patients improves biological availability of morphine and its glucuronide conjugates

The pharmacokinetics of 30 mg nicomorphine after rectal administration with a suppository are described in 8 patients under combined general and epidural anaesthesia. No nicomorphine or 6-mononicotinoylmorphine could be detected in the serum. Morphine appeared almost instantaneously with a lag-time of 8 min and had a final elimination half-life of 1.48 +/- 0.48 h. Morphine was metabolized to morphine-3-glucuronide and morphine-6-glucuronide. These glucuronide conjugates appeared after a lag-time of 12 min and the half-life of these two glucuronide conjugates was similar: about 2.8 h (P > 0.8). The glucuronide conjugate of 6-mononicotinoylmorphine was not detected. In the urine only morphine and its glucuronides were found. The renal clearance value for morphine was 162 ml.min-1 and for the glucuronides 81 ml.min-1. This study shows that administration of a suppository with 30 mg nicomorphine gives an excellent absolute bioavailability of morphine and its metabolites of 88%. The lipid-soluble prodrug nicomorphine is quickly absorbed and immediately hydrolysed to morphine.

Morphine and morphine-glucuronide concentrations in plasma and CSF during long-term administration of oral morphine

Concentrations of morphine, morphine-3-glucuronide (M3G) and morphine-6-glucuronide (M6G) were measured by h.p.l.c. in plasma and cerebrospinal fluid (CSF) samples from 16 patients with cancer receiving oral (controlled-release) morphine. There was a close correlation between plasma and CSF morphine concentrations (r = 0.94, P = 0.0001) and both correlated with drug dosage (r = 0.61, P = 0.013 and r = 0.74, P = 0.0001, respectively). M3G and M6G in plasma and CSF were correlated (r = 0.81 and r = 0.82, both P = 0.0001). No relationship was apparent between M plus M6G concentrations in the CSF and pain scores.

Determination of indomethacin, its metabolites and their glucuronides in human plasma and urine by means of direct gradient high-performance liquid chromatographic analysis. Preliminary pharmacokinetics and effect of probenecid

Indomethacin is metabolized in humans by O-demethylation, and by acyl glucuronidation to the 1-O-glucuronide. Indomethacin, its metabolite O-desmethylindomethacin (DMI) and their conjugates can be measured directly by gradient high-performance liquid chromatographic analysis without enzymic deglucuronidation. The glucuronide conjugates were isolated by preparative HPLC from human urine samples. In plasma only indomethacin was present. No isoglucuronides were present in acidic urine of the volunteer. The possible metabolite deschlorobenzoylindomethacin (DBI) was not detectable in urine. Calibration curves were constructed by enzymic deconjugation of samples containing different concentrations of isolated indomethacin acyl glucuronide, DMI acyl glucuronide and DMI ether glucuronide. The limit of quantitation of indomethacin in plasma is 0.060 microgram/ml. The limits of quantitation in urine are: indomethacin 0.053 microgram/ml, DMI 0.065 microgram/ml, DMI acyl glucuronide 0.065 microgram/ml and DMI ether glucuronide 0.254 microgram/ml. A pharmacokinetic profile of indomethacin is shown, and some preliminary pharmacokinetic parameters of indomethacin obtained from one human volunteer are given. Probenecid inhibits the formation of both the ether and the acyl glucuronide of DMI.

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

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

Pharmacokinetics of intramuscular nicomorphine and its metabolites in man

After i.m. injection nicomorphine is relatively slowly absorbed from the muscular depot and is found in the serum for approximately 1 h. The rate of absorption differs between patients and governs the overall pharmacokinetic profile of the compound. The relative AUCs were nicomorphine 18%, 6-nicotinoylmorphine 17%, and morphine 65%. Nicomorphine and 6-nicotinoylmorphine have significantly higher AUCs after i.m. injection than after i.v. injection, while the AUC of morphine and the total AUC show no difference between the two modes of administration.

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.

Post-operative analgesia by high thoracic epidural versus intramuscular nicomorphine after thoracotomy. Part III. The effects of per- and post-operative analgesia on morbidity

One hundred and twenty-nine patients were subjected to three different types of thoracic operations. The patients were randomly allocated to balanced intravenous anaesthesia including i.v. nicomorphine during surgery and epidural nicomorphine post-operatively (epidural group, n = 58) or to balanced intravenous anaesthesia without i.v. opiates but with high thoracic epidural regional block during the operation and with post-operative intramuscular nicomorphine (intramuscular group, n = 71). Post-operative nicomorphine was only given at the request of the patients, and as frequently as needed to obtain satisfactory pain relief. Patients in the epidural group were given nicomorphine exclusively by epidural injection. Post-operatively, both groups (i.m. and epidural) obtained effective and rapid onset of analgesia, but the pain assessments by the patient and the medical team favoured the epidural group. The requirements of nicomorphine over a period of 3 days were significantly lower in the epidural group 42 mg (s.d. = 18) versus 92 mg (s.d. = 33) in the intramuscular group. Significantly fewer pulmonary complications were observed in the epidural group: 7 atelectases compared to 27 in the intramuscular group. The epidural group showed no signs of ventilatory depression in spite of a catheter inserted at the T3-T4 level.