Clinical Pharmacokinetic and Pharmacodynamic Profile of Cinacalcet Hydrochloride

Cinacalcet hydrochloride (cinacalcet) is a calcimimetic approved for the treatment of secondary hyperparathyroidism in patients with chronic kidney disease (CKD) receiving dialysis and for the treatment of hypercalcaemia in patients with parathyroid carcinoma. Following oral administration, peak plasma concentrations of cinacalcet occur within 2-6 hours. The absolute bioavailability is 20-25%, and administration of cinacalcet with low- or high-fat meals increases exposure (area under the plasma concentration-time curve from time zero to infinity [AUC infinity]) 1.5- to 1.8-fold. Cinacalcet has no significant interaction with calcium carbonate or sevelamer hydrochloride, phosphate binders commonly used in the treatment of patients with CKD receiving dialysis. The terminal elimination half-life is 30-40 hours, and steady-state concentrations are achieved within 7 days. The pharmacokinetics of cinacalcet are dose proportional over the dose range of 30-180 mg. The pharmacokinetic profile of cinacalcet is not notably affected by varying degrees of renal impairment. The pharmacokinetics of cinacalcet are comparable between healthy subjects, patients with primary hyperparathyroidism and patients with secondary hyperparathyroidism with reduced renal function (including those patients with secondary hyperparathyroidism receiving dialysis). Additionally, the pharmacokinetics of cinacalcet are similar in patients with secondary hyperparathyroidism receiving haemodialysis and patients with secondary hyperparathyroidism receiving peritoneal dialysis. Mild hepatic impairment does not affect the pharmacokinetics of cinacalcet, whereas moderate or severe hepatic impairment increases the exposure (AUC(infinity)) by approximately 2- and 4-fold, respectively. Age, sex, bodyweight and race do not notably affect the pharmacokinetics of cinacalcet. Cinacalcet is extensively metabolized by multiple hepatic cytochrome P450 (CYP) enzymes (primarily 3A4, 2136 and 1A2) with <1% of the parent drug excreted in the urine. Dose adjustments of cinacalcet may be necessary, and parathyroid hormone (PTH) and serum calcium concentrations should be closely monitored if a patient initiates or discontinues therapy with a strong CYP3A4 inhibitor (e.g. ketoconazole, erythromycin, itraconazole). Cinacalcet is a strong inhibitor of CYP2D6; therefore, dose adjustment of concomitant medications that are predominantly metabolized by CYP2D6 and have a narrow therapeutic index (e.g. flecainide, vinblastine, thioridazine and most tricyclic antidepressants) may be required. Cinacalcet does not appreciably inhibit or induce the activities of CYP3A4, 1A2, 2C9 or 2C19. An inverse relationship exists between plasma PTH and cinacalcet concentrations. PTH concentrations are greatest before dose administration when the cinacalcet concentration is lowest (24 hours after the previous day's dose). Nadir PTH levels occur approximately 2-3 hours after dosing.