Beta-blockers with SSRIs: the CYP2D6 pairs behind the bradycardia reports

The edition in brief

A British Journal of Clinical Pharmacology scoping review of 48 reports found bradycardia the most frequently described adverse event when beta-blockers and SSRIs are combined, mostly with metoprolol or propranolol alongside fluoxetine, paroxetine or sertraline, and most authors proposed CYP2D6 inhibition as the mechanism. The evidence is mainly case reports, so it signals rather than measures risk, but it points to a simple prescribing choice. Pharmacokinetic modelling from the IMPAACT 2001 study found rifapentine and its metabolite pass into breast milk at about 2% to 4% of maternal plasma levels, with an estimated relative infant dose under 1%, supporting weekly isoniazid–rifapentine during breastfeeding. A therapeutic drug monitoring cohort found co-prescribed valproate lowered dose-corrected quetiapine concentrations by about 17%, an effect confined to women, and its active metabolite by about 24% in everyone. The FDA approved a supplement to a generic buprenorphine application; the public record does not state what changed. The pearl covers rifamycin induction.