The effect of erythromycin, fluvoxamine, and their combination on the pharmacokinetics of ropivacaine.

Abstract

We studied the effect of fluvoxamine and erythromycin on the pharmacokinetics of ropivacaine in a double-blinded, randomized, four-way cross-over study. Eight healthy volunteers ingested daily 1500 mg erythromycin for 6 days, 100 mg fluvoxamine for 5 days (Days 2-6), both erythromycin and fluvoxamine, or placebo. On Day 6, each subject received a single dose of 0.6 mg/kg ropivacaine IV over 30 min. Ropivacaine, 3-hydroxyropivacaine, and 2',6'-pipecoloxylidide in venous plasma and urine samples were measured for up to 12 h and 24 h, respectively. Fluvoxamine increased the area under the drug plasma concentration-time curve (AUC) of ropivacaine 3.7-fold (P: < 0.001), prolonged the elimination half-life (t(1/2)) from 2.3 to 7.4 h (P: < 0.01), and decreased the clearance by 77% (P: < 0.001). Erythromycin alone had only a minor effect on the pharmacokinetics of ropivacaine. However, when compared with fluvoxamine alone, the combination of fluvoxamine and erythromycin further increased the area under the drug plasma concentration-time curve and t(1/2) of ropivacaine by 50% (P: < 0.01). We conclude that inhibition of CYP1A2 by fluvoxamine considerably reduces elimination of ropivacaine. Concomitant use of fluvoxamine and CYP3A4 inhibitor erythromycin further increases plasma ropivacaine concentration by decreasing its clearance. Clinicians should be aware of the possibility of increased toxicity of ropivacaine when used together with inhibitors of CYP1A2. Concomitant use of CYP1A2 and CYP3A4 inhibitors further increases ropivacaine concentration.