NEW YORK (Reuters Health) - A new study of the pharmacokinetics of cinacalcet HCl (Sensipar) shows that plasma levels of the drug increase linearly with dose over the clinical dose range, and that the drug reaches steady-state levels in the blood within 4 days of initiating treatment.
“Physicians still need to follow the guidelines in the package insert with regard to dosage and titration,” Dr. Desmond Padhi, study co-author and director in early development at Amgen, Inc., the drug’s maker, told Reuters Health.
Nevertheless, the findings show a straightforward relationship between dosage and plasma levels, “which is I think a comforting thing to a physician,” Dr. Robert Harris, lead author of the study and associate director for pharmacokinetics at Amgen, Inc.,Thousand Oaks, California, added in an interview.
Approved by the FDA last March, Sensipar is indicated for treating secondary hyperparathyroidism in patients with chronic kidney disease who are on dialysis, as well as hypercalcemia in patients with parathyroid carcinoma. The drug reduces parathyroid hormone levels without increasing levels of calcium or phosphorous, a common drawback of traditional treatments for the condition, such as vitamin D.
The current study, published in the December issue of the American Journal of Kidney Diseases, was conducted to evaluate the safety and tolerability of the drug at doses up to 300 mg and to characterize the drug’s pharmacokinetic profile, Dr. Harris said. Twenty-three patients on dialysis were assigned in a 4 to 1 ratio to receive cinacalcet or placebo. Ten patients completed the study.
The drug was titrated weekly in 25 mg increments from 25 to 300 mg/day. Up to 200 mg, the researchers found, the pharmacokinetics were linear, while there was no substantial increase in exposure to the drug at higher doses. While the study was not conducted to evaluate the effectiveness of the drug, it did find that plasma parathyroid hormone decreased with increases in cinacalcet concentration.
“Based on these results, an added therapeutic benefit at single daily doses greater than 200 mg is unlikely,” the researchers conclude.
Source: Am J Kidney Dis 2004;44:1070-1076. [ Google search on this article ]
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