Bromocriptine × Erythromycin

Bromocriptine is broken down in the liver by CYP3A4, and erythromycin inhibits this enzyme. With erythromycin, bromocriptine area under the curve (AUC) rose 2.8- to 3.7-fold and peak concentration 4.6-fold.

Bromocriptine side effects get stronger: nausea, vomiting, headache, dizziness, a drop in blood pressure on standing (rarely with fainting), drowsiness, confusion and hallucinations.

Avoid the combination. The intravenous erythromycin label advises against using it with dopaminergic ergot alkaloids, the group that includes bromocriptine. It allows erythromycin with bromocriptine only if bromocriptine effects and side effects can be closely monitored; otherwise bromocriptine is stopped for the erythromycin course (erythromycin label). The bromocriptine dose may need to be lowered during co-administration (erythromycin label). The bromocriptine label advises caution with macrolides because they raise bromocriptine levels (bromocriptine label). For the bromocriptine formulation used in type 2 diabetes in the US, the US Food and Drug Administration (FDA) caps the dose at 1.6 mg a day with erythromycin (bromocriptine FDA label).