Verapamil induces increased bone volume and osteopenia in female rats but has the opposite effect in male rats.

Verapamil inhibits the intestinal absorption of calcium (Ca) and increases serum parathyroid hormone in rats. The effects of verapamil on bone tissue after long-term treatment is, however, not well described. Adult female and male Sprague-Dawley rats received verapamil in their drinking water at a dosage of 0.075 mg/ml (low dose) or 0.75 mg/ml (high dose) for 12 weeks; control rats received only drinking water. All rats were fed a diet containing 0.1% Ca and 0.5% P. In female rats, the amount of bone ash per volume was significantly reduced from 0.742 g/ml in controls to 0.713 g/ml after low-dose treatment of verapamil, and to 0.667 g/ml following high-dose treatment (P less than 0.01). The tibial length was increased from 39.7 mm in controls to 40.3 mm or to 40.7 mm after low or high doses (P less than 0.01). The tibial volume increased from 0.385 ml in controls to 0.397 ml after low doses and to 0.429 ml after high doses (P less than 0.01). In contrast, in male rats the amount of bone ash per volume was significantly increased from 0.578 g/ml in controls to 0.580 g/ml after low doses and to 0.620 g/ml after high doses of verapamil (P less than 0.01). The tibial bone volume in males as decreased from 0.633 ml in controls to 0.641 ml after low doses and to 0.583 ml after high doses (P less than 0.05). The tibial length in the males was not changed by verapamil.(ABSTRACT TRUNCATED AT 250 WORDS)