A retrospective cohort study exploring diltiazem as a pharmaco-enhancer for tacrolimus, in a post-heart transplant...

A significant proportion of heart transplant-associated expenditure are attributable to immunosuppressants. Post-transplant hypertension adds to the pill burden and subsequent costs. In this study, we describe the effect of diltiazem-the antihypertensive and pharmaco-enhancer-on reducing the required oral dose of tacrolimus.

We included 17 recipients who had successfully undergone heart transplants but later developed post-transplant hypertension and were treated with diltiazem. Serum trough levels of the immunosuppressant tacrolimus were measured every 2 weeks. Required doses before and after the introduction of diltiazem were compared. Patients were assessed at each follow-up visit for any evidence of toxicity. Medication-related expenditure was estimated based on government-mandated standardized retail price.

The power of the study was 98.92% at α = 0.05. The mean tacrolimus dose required prior to initiation of diltiazem was 5.85 ± 1.55 mg. After initiating diltiazem, the mean required doses reduced to 2.88 ± 1.24 mg (p < .0001). Relatively, the required doses reduced by 52.4 ± 10.9%-independently of age, sex, and dose of diltiazem. Medication-related monthly expenditure reduced by 50.3 ± 10.4%. No patient demonstrated evidence of toxicity.

Concomitant use of diltiazem and tacrolimus can safely, effectively, and predictably reduce the required dose of tacrolimus and significantly reduce corresponding costs.