The effect of AST-120 on the single-dose pharmacokinetics of metoprolol extended-release tablets in healthy subjects.

Background: This was a randomized, open-label, three-way crossover study to assess the effects of AST-120 (an orally administered spherical carbon adsorbent acting in the gastrointestinal tract without systemic circulation) on the single-dose pharmacokinetics of metoprolol in an extended-release formulation (metoprolol ER) in healthy volunteers.

Methods: A total of 34 subjects were singly administered metoprolol ER alone (A), and metoprolol ER in combination with AST-120 simultaneously (B) and 1 h later (C).

Results: The total exposure was more significantly reduced in both treatments B and C than that in treatment A; the geometric mean ratios of area under the curve extrapolated to infinity (AUC0-∞) for B/A and C/A were reduced by approximately 30% in both treatments B and C. Maximum observed plasma concentration (Cmax) of metoprolol in treatment B significantly decreased, whereas Cmax in treatment C was slightly decreased. AST-120 treatment was unlikely to affect apparent first-order terminal elimination half-life (T1/2) of metoprolol significantly. Reduction in heart rate and blood pressure readings were similar across the treatment periods. Coadministration of AST-120 and metoprolol ER was safe and was well tolerated.

Conclusions: Because AST-120 reduced gastrointestinal absorption of metoprolol ER, careful monitoring of heart rate and blood pressure is recommended in coadministration of AST-120 with metoprolol ER.