Drug Interaction Report

MONITOR: Somatostatin analogs (e.g., octreotide, lanreotide) can decrease heart rate and may potentiate the bradycardic effects of drugs like beta-blockers, calcium channel blockers, digitalis glycosides, and certain antiarrhythmic agents (e.g., class I antiarrhythmics, adenosine, amiodarone). Octreotide has commonly been associated with bradycardia (less than 50 bpm), conduction abnormalities, and arrhythmias in acromegalic patients. Occasional cases of sinus bradycardia and ventricular tachycardia have also been reported with lanreotide.

MANAGEMENT: Caution is advised if somatostatin analogs are prescribed with agents that exhibit bradycardic effects, including ophthalmic formulations of beta-blockers. Heart rate and blood pressure should be monitored.

MONITOR: Due to their gastrointestinal pharmacologic effects, somatostatin analogs (e.g., octreotide, lanreotide) may variously affect the absorption of dietary nutrients and concomitantly administered oral medications. Somatostatin analogs have been shown to prolong gastrointestinal transit time and inhibit intestinal absorption of some nutrients such as fat. Clinical data are limited, however. In case reports, octreotide has been reported to reduce the relative bioavailability of cyclosporine. Transplant rejection and significant reductions in cyclosporine levels, sometimes to undetectable levels, have been reported in association with the interaction. Vitamin K absorption was not affected when concomitantly administered with lanreotide according to the manufacturer.

MANAGEMENT: Clinicians should be aware of the potential for altered absorption of concomitantly administered oral medications during treatment with somatostatin analogs. Blood levels and clinical response should be monitored, particularly for drugs that have a narrow therapeutic index, and the dosages adjusted as necessary.