A 51-year-old patient, who takes a calcium channel blocker (CCB), reports that he is experiencing constipation. Which CCB is the patient most likely to be taking?

All calcium channel blockers (CCBs) can cause constipation by relaxing the smooth muscle of the gastrointestinal tract, which slows motility. However, this effect is most pronounced with the non-dihydropyridine CCBs, particularly verapamil. Verapamil has a significant effect on GI smooth muscle, making constipation one of its most common and often dose-limiting side effects. While other CCBs can cause this adverse effect, the incidence and severity are highest with verapamil, making it the most likely agent in this scenario.

A. Nifedipine: As a dihydropyridine, nifedipine has a lower incidence of constipation compared to non-dihydropyridine agents like verapamil.
B. Amlodipine: Amlodipine, a dihydropyridine, is more commonly associated with peripheral edema and is less likely to cause significant constipation than verapamil.
D. Diltiazem: Although a non-dihydropyridine, diltiazem is generally less constipating than verapamil, having an intermediate side effect profile.

1. Katzung

B. G.

& Vanderah

T. W. (2021). Basic & Clinical Pharmacology (15th ed.). McGraw-Hill Education. Chapter 12

"Vasodilators & the Treatment of Angina Pectoris

" Section: Toxicity of Calcium Channel Blockers. The text states

"Constipation is a common dose-limiting side effect

especially with verapamil."

2. Brunton

L. L.

Knollmann

B. C.

& Hilal-Dandan

R. (Eds.). (2023). Goodman & Gilman's: The Pharmacological Basis of Therapeutics (14th ed.). McGraw-Hill Education. Chapter 29

"Calcium Channel Blockers

" Section: Adverse Effects. The text notes that constipation is a frequent adverse effect of verapamil

occurring in about 25% of patients.

3. University of Michigan

College of Pharmacy. (n.d.). Pharmacotherapy of Hypertension. PTP 631 Course Materials. The course notes compare the adverse effect profiles of CCBs

highlighting that constipation is most common with verapamil among all calcium channel blockers.