Impact of age, weight and concomitant treatment on lamotrigine pharmacokinetics.

WHAT IS KNOWN AND OBJECTIVE: Lamotrigine metabolism may be substantially altered with concomitant administration of valproic acid and/or carbamazepine. Such alterations may require the adjustment of lamotrigine dose to ensure optimal treatment efficacy and safety. METHODS: The extent of lamotrigine interactions was investigated dependent on age, gender, weight and dose of concomitant carbamazepine and/or valproic acid in 65 patients with epilepsy. Lamotrigine plasma steady-state oral clearance (CLss/F) and area under the curve (AUCss) were calculated from the dose of drug, average steady-state concentration (Css) and interval of administration. Multiple regression analysis was used for the identification and quantification of factors that influenced lamotrigine pharmacokinetics. RESULTS AND DISCUSSION: Age and dose of carbamazepine and valproic acid had significant influence on lamotrigine CLss/F and AUCss. Carbamazepine was associated with a dose-dependent increase and valproic acid with a dose-dependent decrease of lamotrigine metabolism rate. The effect of carbamazepine was more pronounced. Younger patients were expected to metabolize lamotrigine more rapidly whereas overweight patients may be less susceptible to interactions. Gender had no influence on lamotrigine pharmacokinetics. WHAT IS NEW AND CONCLUSION: The efficacy and safety of lamotrigine may be altered by concomitant administration of carbamazepine and valproic acid. The models developed may be useful for estimating doses of lamotrigine for individual patients to minimize clinically significant interactions. Therapeutic monitoring is advisable when those drugs are used concomitantly.

Prevalence of menstrually related migraine and nonmigraine primary headache in female students of Belgrade University.

OBJECTIVES: To determine prevalence and characteristics of menstrually related migraine and nonmigraine headache in female students of Belgrade University. METHODS: A questionnaire was administered to female students during randomly selected classes of the Schools of Medicine and Pharmacy. Diagnoses were assigned according to the criteria of the International Headache Society and MacGregor's stricter definition of "menstrual" migraine. RESULTS: Of 1943 female students (18 to 28 years old), 1298 (66.8%) had primary headaches. Among 1298 students with headache, 245 (12.6%) had migraine and 1053 (54.2%) had nonmigraine headache. The prevalence rates of migraine versus nonmigraine headache in relation to the menstrual cycle were: premenstrual, 0.9% versus 4.4%; menstrual, 1.5% versus 1.5%; menstrually associated, 6.1% versus 10.1%; menstrually unchanged, 2.7% versus 19.2%; and menstrually unrelated, 1.4% versus 18.9%. Female students with migraine had menstrually related attacks more frequently than students with nonmigraine headache (67.7% versus 29.5%). This difference was most prominent among students with menstrual migraine compared with students with menstrual nonmigraine headache (12.2% versus 2.7%). Exacerbation of migraine during menstruation was slightly more severe and more complex than exacerbation of nonmigraine headache. Female students with migraine versus nonmigraine headache did not differ significantly in age, age at onset of menarche, or age at onset of headache. Female students with migraine were significantly more likely to report a positive family history for migraine and menstrual migraine, severe attacks, reduced work activity, and aura. CONCLUSION: The results obtained are in accord with the prevailing opinion that there is a relationship between migraine and female sex hormones, and suggest that women with nonmigraine headache are also susceptible to hormonal fluctuations.

Urinary excretion of phenobarbital and its metabolite p-hydroxyphenobarbital in convulsing and non-convulsing patients.

As part of an investigation of phenobarbital (PB) pharmacokinetics in patients with status epilepticus (SE), urinary excretion of PB and its main metabolite, hydroxyphenobarbital (HPB), was studied in patients who had an episode of SE, as well as in non-convulsing ones. Eleven in-patients were studied:(group 1) five patients (4 M + 1 F; 48 +/- 28 years old; 64 +/- 6 kg body weight; mean +/- SD) with convulsive status epilepticus, and (group 2) six patients (5 M + 1 F; 37 +/- 13 years old; 71 +/- 15 kg body weight) with epilepsy, seizure-free at the moment of PB administration and without established anti-epileptic therapy. All subjects received a single intravenous dose of PB (15 mg/kg) at a rate of 100 mg/min. PB and HPB concentrations were measured by high performance liquid chromatography with UV detection at 220 nm in urine samples collected throughout 24 h. The comparison of pharmacokinetic parameters of urinary excretion of PB and HPB showed a statistically significant difference in the values of recovery of HPB and total barbiturate (higher values in the patients with SE) in 24 h urine. Differences in the excretion of PB between the two groups of patients--higher values in the patients who had had an episode of SE, and in urine flow--slightly elevated volumes in the same group, failed to reach statistical significance, probably due to the small number of participants in the study.

Comparative pharmacokinetics and bioavailability of two cotrimoxazole preparations.

The objective of this study was to assess both pharmacokinetic properties and bioavailability of a newly developed cotrimoxazole preparation (Bioprim tablets, 80 mg of trimethoprim/400 mg sulfamethoxazole), in comparison with a reference preparation commercially available (Bactrim tablets, 80 mg of trimethoprim/400 mg of sulfamethoxazole). The pharmacokinetics and bioavailability of cotrimoxazole from these preparations were compared in an open randomized crossover study in 12 healthy males. Plasma concentrations of trimethoprim and sulfamethoxazole were measured by HPLC after protein precipitation. Noncompartmental pharmacokinetic analysis was performed on the plasma concentration-time data. The obtained pharmacokinetic values (Cmax, tmax, beta, t1/2 beta, CL, Vd, AUC36, AUC infinity) of both trimethoprim and sulfamethoxazole determined in our study agreed with values reported in the literature. Westlake's and Nonparametric probability tests with the 90% confidence intervals, for both trimethoprim and sulfamethoxazole gave the differences within 80 and 120%, for all necessary measures (Cmax, tmax and AUC infinity). Statistical analysis of the data has shown that the preparations have similar pharmacokinetic profiles and therefore can be considered equally bioavailable.