Determination and pharmacokinetics of dextromoramide in methadone maintenance therapy

To study the pharmacokinetics of dextromoramide in long-term opiate addicts on methadone maintenance therapy (MMT) a reverse-phase HPLC technique was developed to monitor dextromoramide and methadone concentrations in plasma simultaneously. After liquid-liquid extraction from plasma, dextromoramide and methadone were determined using a Supelcosil LC-ABZ column and a mobile phase of KH2 phosphate buffer (25 mM, pH 2.5) mixed with acetonitrile (80:20, v/v) and UV detection at 206 nm. The method was found to be sufficiently sensitive, specific and reproducible to apply in six subjects on MMT for many years, receiving orally administered dextromoramide as adjuvant. Pharmacokinetic data sets for dextromoramide in each subject were conducted and analysed further, indicating short elimination half-life values (71 min, range 31-152 min). Contrary to previous studies, in all subjects tested the pharmacokinetics of dextromoramide are best described using an one-compartment model.

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.

A dextromoramide-related fatality

A 38-year-old man was found in his car suffering from a heart attack. Serum analysis by capillary gas chromatography and mass spectrometry confirmed the presence of dextromoramide (Palfium), methadone, and lidocaine. The serum concentrations at admission to the hospital were: 1.9 micrograms/mL of dextromoramide, 0.4 micrograms/mL of methadone, and 0.4 micrograms/mL of lidocaine. A serum alcohol analysis performed using headspace gas chromatography was negative.

[Pharmacokinetics of dextromoramide in the surgical patient]

The pharmacokinetics of dextromoramide were studied in nine patients undergoing peripheral vascular surgery. All the patients were anaesthetised with thiopentone and vecuronium. After tracheal intubation, anaesthesia was maintained with 0.5 to 1.5 vol % halothane and a 60%-40% vol nitrous oxide-oxygen mixture. Once the patient's status was stable, a 0.8 mg.kg-1 bolus of dextromoramide was given intravenously. Blood samples were obtained 2, 5, 10, 30, 60, 90, 120, 180, 240, 300, 360, and 420 min afterwards by an arterial catheter. Dextromoramide serum concentrations were measured with high performance liquid chromatography after extraction with an original technique. The pharmacokinetic parameters were calculated by computer using TRIOMPHE. In five patients, a bi-exponential equation best fitted the results, whereas a tri-exponential equation was necessary for the other four. Mean elimination half-life was 215.3 +/- 78.4 min, and the apparent final volume of distribution was 0.58 +/- 0.20 l.kg-1. Hepatic extraction was low, as shown by a mean systemic clearance of 2.0 +/- 0.9 ml.kg-1.min-1. Liposolubility of this drug is the highest of all opiates, with a heptane/water partition coefficient of 12.3. These parameters demonstrate that, in the opiate drug group, dextromoramide has a place apart from the others.

Toxicological findings after fatal dextromoramide injection

A death involving dextromoramide injection is presented. The drug was analyzed in whole blood, bile, stomach contents, kidney, brain and liver. The whole blood concentration was 1526 ng/ml. The results are compared with the existing literature.