Interaction between sotalol and an antacid preparation

AIMS: The aim of the study was to investigate the pharmacokinetic interaction between sotalol and antacids, and its pharmacodynamic relevance. METHODS: In a randomized cross-over design with three treatment groups, six healthy volunteers received orally either 160 mg of sotalol alone (phase 1), or 160 mg sotalol plus 20 ml of a suspension of an antacid (MAH; magnesium hydroxide (1200 mg) and aluminium oxide (1800 mg)) (phase 2) or 160 mg sotalol plus the antacid given 2 h after sotalol administration (phase 3). Heart rate and plasma sotalol concentrations were measured before and 1, 2, 3, 4, 6, 8, 12 and 24 h after sotalol administration. Urinary sotalol excretion was measured for 24 h after sotalol application. RESULTS: Cmax of sotalol decreased from 1.22 +/- 0.22 mgl-1 (phase 1) to 0.89 +/- 0.29 mgl-1 (phase 2) and increased again to 1.27 +/- 0.18 mgl-1 in phase 3. A similar significant change was noted in AUC (15.6 +/- 2.75 mgl-1, 12.3 +/- 3.04 mg h l-1 and 15.0 +/- 2.06 mgl-1) and in the amount of cumulative urinary excretion (79.2 +/- 11.1 mg, 72.1 +/- 11.2 mg and 80.6 +/- 7.9 mg), respectively. tmax and elimination half-life (t1/2,z) of sotalol remained unchanged in the presence of MAH. After combined administration with MAH, the area under the heart rate curve of sotalol was reduced between 0 and 4 h when compared across treatments. CONCLUSIONS: Combined administration of sotalol and MAH decreased the serum sotalol levels. The interaction can be avoided by a two hour interval between application of these drugs.