Pharmacokinetics of rizatriptan in healthy elderly subjects

OBJECTIVE

Rizatriptan is a serotonin 5-HT1B/1D receptor agonist for acute treatment of migraine. Its pharmacokinetics were assessed in healthy elderly males and females receiving a single 10 mg tablet oral dose. The pharmacokinetic data (AUC(0-infinity) and Cmax) for the elderly in this study were compared with historical data from previous studies for healthy young adults (n = 65).

METHODS

In a double-blind, parallel, placebo-controlled study, healthy elderly female and male subjects aged 65 or older (n = 8 each) received a single oral dose of 10 mg rizatriptan. Plasma and urine concentrations of drug were determined by HPLC with tandem mass spectrometry detection at several collection time points or intervals starting at predose and postdose over 24 h.

RESULTS

In elderly subjects, the geometric mean values for AUC(0-infinity) and Cmax were 77.7 ng/h/ml and 21.9 ng/ml; the average values for tmax, half-life (t 1/2), renal clearance (Clr), and percent urinary excretion of dose (Ue) were 1.2 h, 1.8 h, 197 ml/min and 9.3%, respectively. The AUC(0-infinity) and Cmax of rizatriptan were similar in elderly and young subjects. The geometric mean AUC ratio of elderly to young was 0.96 with 90% confidence interval (0.83, 1.11), p > 0.25. The geometric mean Cmax ratio was 0.89 with 90% confidence interval (0.72, 109), p > 0.25. No significant pharmacokinetic differences were observed between elderly males and females.

CONCLUSIONS

The plasma pharmacokinetics of rizatriptan appear to be similar in the elderly and young. In the elderly, the pharmacokinetics of rizatriptan do not appear to differ between male and female to a clinically significant extent.

Grapefruit juice has minimal effects on plasma concentrations of lovastatin-derived 3-hydroxy-3-methylglutaryl coenzyme A reductase inhibitors

OBJECTIVE

To evaluate the effect of regular-strength grapefruit juice, a cytochrome P4503A4 (CYP3A4) inhibitor, on the pharmacokinetics of a commonly prescribed regimen of oral lovastatin.

METHODS

In a randomized crossover study, 16 healthy subjects received a single 40 mg dose of lovastatin in the evening after each consumed an 8-ounce glass of regular-strength grapefruit juice or water with breakfast for 3 consecutive days. The effect of the same grapefruit juice and water regimen on the pharmacokinetics of midazolam (2 mg oral dose given 1 hour after the third day of grapefruit juice and water) was used as a positive control in the same subjects. Plasma concentrations of 3-hydroxy-3-methylglutaryl coenzyme A (HMG-CoA) reductase inhibitors were determined by an enzyme inhibition assay, and concentrations of lovastatin, lovastatin acid, and midazolam were determined by liquid chromatography-tandem mass spectrometry.

RESULTS

The area under the plasma concentration-time profiles (AUC) and maximum plasma concentrations (Cmax) of HMG-CoA reductase inhibitors increased slightly (-30% for each) after consumption of grapefruit juice. Similar effects on AUC and Cmax (approximately 40% increase for each) were noted after analysis of samples of hydrolyzed plasma (which converts inactive lactones to active hydroxy acid species). The AUC and Cmax values for lovastatin approximately doubled in the presence of grapefruit juice, whereas the same parameters for lovastatin acid increased 1.6-fold. Grapefruit juice caused the AUC for midazolam to increase by a factor of approximately 2.4.

CONCLUSIONS

Daily consumption of a glass of regular-strength grapefruit juice has a minimal effect on plasma concentrations of HMG-CoA reductase inhibitors (approximately 30% to 40% increase) after a 40 mg evening dose of lovastatin.