A 78-year-old man returns to the clinic 3 weeks after starting verapamil (Calan SR) 180 mg daily for hypertension and rate control. His BP is now at goal, but he reports persistent, severe constipation that did not exist before the medication change. He has tried increased dietary fiber and water without relief. Which of the following BEST explains his new symptom?

Question

Accepted Answer

✅ C. Verapamil-induced constipation, a classic dose-dependent adverse effect
Constipation is THE signature adverse effect of verapamil, occurring in approximately 25% of patients and significantly more than with any other CCB. The mechanism is inhibition of calcium-dependent smooth muscle contraction in the colon, slowing peristalsis. This effect is so common and so specific to verapamil that it is a high-yield board pearl. Management includes dose reduction, switching to a different antihypertensive class (or even diltiazem, which causes much less constipation), and adding an osmotic laxative if the drug must be continued.

❌ A. Colon cancer, given age and new constipation
While new constipation in an elderly patient always warrants evaluation for colorectal malignancy, the temporal relationship with verapamil initiation and the drug's well-documented adverse-effect profile make iatrogenic constipation the most likely cause. A medication trial discontinuation (or dose reduction) is the logical first step before extensive workup, though age-appropriate colon cancer screening should still be confirmed.

❌ B. Hypothyroidism
Hypothyroidism can cause constipation but would typically present with other features such as cold intolerance, fatigue, weight gain, dry skin, and bradycardia, and would not have a 3-week temporal link to a new medication.

❌ D. Dietary fiber deficiency as the sole cause
The patient already tried increased fiber and water without improvement, and the clear temporal link to verapamil initiation makes a drug effect the most parsimonious explanation.

:::pearl
CCB adverse-effect memory aids: verapamil causes constipation (the big one), amlodipine/dihydropyridines cause peripheral edema and reflex tachycardia, diltiazem sits in between with modest constipation and edema rates. If the board mentions new constipation after starting a BP med, think verapamil.
:::

Verapamil

✅ Indications

⚙️ Mechanism of Action

📏 Dosing

🚫 Contraindications

⚠️ Adverse Effects

🔬 Monitoring

💎 Board Pearls

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