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Lack of effect of St John's Wort on carbamazepine pharmacokinetics in healthy volunteers
Author(s) -
Burstein Aaron H.,
Horton Ralph L.,
Dunn Timothy,
Alfaro Raul M.,
Piscitelli Stephen C.,
Theodore William
Publication year - 2000
Publication title -
clinical pharmacology and therapeutics
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.941
H-Index - 188
eISSN - 1532-6535
pISSN - 0009-9236
DOI - 10.1067/mcp.2000.111530
Subject(s) - carbamazepine , pharmacokinetics , pharmacology , anticonvulsant , hypericin , plasma concentration , hypericum perforatum , blood sampling , medicine , chemistry , epilepsy , psychiatry
Background St John's Wort is a popular herbal product used by approximately 7% of patients with epilepsy. Previous reports have described reductions in concentrations of CYP3A4 substrates indinavir and cyclosporine (INN, ciclosporin) associated with St John's Wort. Objective Our objective was to determine the effect of St John's Wort on steady state carbamazepine and carbamazepine‐10,11‐epoxide pharmacokinetics. Methods and Subjects Eight healthy volunteers (5 men; age range, 24–43 years) participated in this unblinded study. Subjects received 100 mg of carbamazepine twice daily for 3 days, 200 mg twice daily for 3 days, and then 400 mg once daily for 14 days. Blood samples were collected before and 1, 2, 4, 6, 8, 10, 12, and 24 hours after the dose on day 21. The subjects then took 300 mg of St John's Wort (0.3% hypericin standardized tablet) 3 times daily with meals and with carbamazepine for 14 days. On day 35, blood sampling was repeated. Plasma samples were analyzed for carbamazepine and carbamazepine‐10,11‐epoxide with HPLC. We compared carbamazepine and carbamazepine‐10,11‐epoxide noncompartmental pharmacokinetic parameter values before and after St John's Wort with a paired Student t test. Results We found no significant differences before or after the administration of St John's Wort in carbamazepine peak concentration (7.2 ± 1 mg/L before versus 7.6 ± 1.3 mg/L after), trough concentration (4.8 ± 0.5 mg/L before versus 4.3 ± 0.8 mg/L after), area under the plasma concentration‐time curve (142.4 ± 12.9 mg · h/L before versus 143.8 ± 27.2 mg · h/L after), or oral clearance (2.8 ± 0.3 L/h before versus 2.9 ± 0.6 L/h after). Similarly, no differences were found in peak concentration (2 ± 0.5 mg/L before versus 2.1 ± 0.4 mg/L after), trough concentration (1.3 ± 0.3 mg/L before versus 1.4 ± 0.3 mg/L after), and area under the plasma concentration‐time curve (37.5 ± 7.4 mg · h/L before versus 41.9 ± 10.3 mg · h/L after) of carbamazepine‐10,11‐epoxide. Conclusions The results suggest that treatment with St John's Wort for 14 days did not further induce the clearance of carbamazepine. (Clin Pharmacol Ther 2000;68:605–12.) Clinical Pharmacology & Therapeutics (2000) 68 , 605–612; doi: 10.1067/mcp.2000.111530