The pharmacokinetics, safety and tolerability of the co-administration of diethylcarbamazine and albendazole.

The pharmacokinetics, safety and tolerability of single, oral doses of diethylcarbamazine (DEC) and albendazole, given alone or in combination, were investigated in a double-blind, randomized and placebo-controlled trial involving 42 amicrofilaraemic subjects living in an area of India where lymphatic filariasis is endemic. The subjects (34 males and eight females, aged 18-52 years and weighing 46-66.5 kg) were randomly allocated to one of the three drug groups. Fourteen were given just DEC (6 mg/kg), another 14 were given just albendazole (400 mg) and the remaining 14 were given both DEC (6 mg/kg) and albendazole (400 mg). Blood samples for pharmacokinetic study were collected at specified intervals before and after drug administration. Plasma concentrations of DEC and albendazole/albendazole sulphoxide were estimated using gas chromatography and HPLC, respectively. The safety and tolerability of the treatments were evaluated through clinical and laboratory assessments. Both the DEC and albendazole were well tolerated when given alone or in combination, no adverse events being observed. In all three treatment groups, the drugs were rapidly absorbed from the gastro-intestinal tract although there was marked inter-individual#10; variation. The pharmacokinetics of DEC, albendazole and albendazole sulphoxide were similar, whether each drug was given alone or in combination. These results indicate that there is no adverse pharmacokinetic or pharmacodynamic reason why DEC and albendazole should not be co-administered to control lymphatic filariasis.

A urine metabolic ratio of dextromethorphan and 3-methoxymorphinan as a probe for CYP3A activity and prediction of cyclosporine clearance in healthy volunteers.

Dextromethorphan (DM) is metabolized in the body to dextrophan (DT) and 3-methoxymorphinan (3-MM) by cytochrome P450 (CYP) 2D6 and 3A4, respectively, and cyclosporine (CsA) is a known substrate of CYP3A4. We attempted to determine if the urine metabolic ratio of DM:3-MM at various time intervals during 24 hours is predictive of CsA clearance in 11 healthy volunteers. Each subject took DM 30 mg orally, and serial urine samples were collected at 0-4, 4, and 4-24, and 0-24 hours. Subjects then were randomly assigned to receive either oral microemulsion CsA 5 mg/kg or intravenous CsA 1.5 mg/kg in a crossover fashion in a two-sequence pharmacokinetic study with a wash-out period of at least 7 days. A total of 17 blood samples were collected from each subject in the CsA pharmacokinetic study over 24 hours. Urinary DM, DT, and 3-MM were quantified by high-performance liquid chromatography (HPLC) with a fluorescence detector, and blood CsA concentrations were analyzed by HPLC with ultraviolet detection. All subjects were extensive metabolizers of CYP2D6 as determined by metabolic ratios of DM:DT (mean+/-SD 0.0255+/-0.048). There was no correlation between CYP2D6 and CYP3A4 (p=0.38). The metabolic ratios of DM:3-MM in any urine samples during the 24-hour collection period did not predict CsA pharmacokinetics, although the 0-24 hour sample had an unexpected positive correlation with CsA clearance (r2 = 0.38, p<0.0001). The correlation was similar for metabolic ratios of DM:3-MM with intravenous CsA clearance (r2 = 0.5, p<0.0001). Metabolic ratios of DM:3-MM based on 24-hour cumulative urine collection did not appear to have clinical utility in predicting CYP3A activity measured by CsA clearance.

Clinical pharmacokinetics of suramin in patients with onchocerciasis.

OBJECTIVE: Ten male patients with onchocerciasis received six weekly infusions of suramin according to the WHO-recommended regimen. RESULTS: In no case did the plasma concentration of suramin exceed 300 mg x l(-1), and serious toxicity was not observed. The apparent volume of distribution (median 20.6 l) was comparable to that reported for patients with prostatic carcinoma. Elimination from patients with onchocerciasis was relatively slow (median plasma clearance 6.2 ml x h(-1), median terminal elimination half-life 91.8 days). CONCLUSION: Microfilariae were eliminated in eight out of ten patients. Spontaneous nodule regression was noted in four patients.

The pharmacokinetics and bioavailability of dihydroartemisinin, arteether, artemether, artesunic acid and artelinic acid in rats.

The pharmacokinetics and bioavailability of dihydroartemisinin (DQHS), artemether (AM), arteether (AE), artesunic acid (AS) and artelinic acid (AL) have been investigated in rats after single intravenous, intramuscular and intragastric doses of 10 mg kg(-1). Plasma was separated from blood samples collected at different times after dosing and analysed for parent drug. Plasma samples from rats dosed with AM, AE, AS and AL were also analysed for DQHS which is known to be an active metabolite of these compounds. Plasma levels of all parent compounds decreased biexponentially and were a reasonable fit to a two-compartment open model. The resulting pharmacokinetic parameter estimates were substantially different not only between drugs but also between routes of administration for the same drug. After intravenous injection the highest plasma level was obtained with AL, followed by DQHS, AM, AE and AS. This resulted in the lowest steady-state volume of distribution (0.39 L) for AL, increasing thereafter for DQHS (0.50 L), AM (0.67 L), AE (0.72 L) and AS (0.87 L). Clearance of AL (21-41 mL min(-1) kg(-1)) was slower than that of the other drugs for all three routes of administration (DQHS, 55-64 mL min(-1) kg(-1); AM, 91-92 mL min(-1) kg(-1); AS, 191-240 mL min(-1) kg(-1); AE, 200-323 mL min(-1) kg(-1)). In addition the terminal half-life after intravenous dosing was longest for AL (1.35 h), followed by DQHS (0.95 h), AM (0.53 h), AE (0.45 h) and AS (0.35 h). Bioavailability after intramuscular injection was highest for AS (105%), followed by AL (95%) and DQHS (85%). The low bioavailability of AM (54%) and AE (34%) is probably the result of slow, prolonged absorption of the sesame-oil formulation from the injection site. After oral administration, low bioavailability (19-35%) was observed for all five drugs. In-vivo AM, AE, AS and AL were converted to DQHS to different extents; the ranking order of percentage of total dose converted to DQHS was AS (25.3-72.7), then AE (3.4-15.9), AM (3.7-12.4) and AL (1.0-4.3). The same ranking order was obtained for all formulations and routes of administration. The drug with the highest percentage conversion to DQHS was artesunic acid. Because DQHS has significant antimalarial activity, relatively low DQHS production could still contribute significantly to the antimalarial efficacy of these drugs. This is the first time the pharmacokinetics, bioavailability and conversion to DQHS of these drugs have been directly compared after different routes of administration. The results show that of all the artemisinin drugs studied the plasma level was highest for artelinic acid; this reflects its lowest extent of conversion to DQHS and its slowest rate of elimination.