Cinacalcet does not affect the pharmacokinetics or pharmacodynamics of warfarin.
OBJECTIVE
Cinacalcet HCl (cinacalcet), approved for secondary hyperparathyroidism and parathyroid carcinoma-associated hypercalcaemia, may be coadministered with warfarin. The purpose of this study was to determine the pharmacokinetics/pharmacodynamics and tolerability of warfarin during cinacalcet coadministration.


METHODS
In this phase 1, randomised, double-blind, placebo-controlled, two-treatment, two-period crossover study, 21 healthy subjects received oral cinacalcet (30 mg) or placebo twice a day for 7 days and once on day 8, with a single warfarin dose (25mg) on day 5. After a 3-week washout, subjects received the alternative treatment. Samples for warfarin pharmacokinetics/pharmacodynamics were obtained until 144 hours post-dose.


RESULTS
Single-dose administration of warfarin to subjects receiving cinacalcet did not demonstrate altered pharmacodynamics of either the R- or S-enantiomer. Geometric means ratio (90% CIs) for R- and S-warfarin were 1.01 (0.95, 1.07) and 1.00 (0.94, 1.04), respectively, for the area under the plasma concentration-time curve from time 0 to infinity (AUC(infinity)) and 0.90 (0.84, 0.96) and 0.88 (0.83, 0.94), respectively, for observed maximum plasma concentrations (C(max)). Additionally, the pharmacokinetic profiles of R- or S-warfarin were similar for all subjects. The ratio for the AUC from time 0 to the last measurable concentration (AUC(t)) for prothrombin time and factor VII were 1.03 (1.01, 1.04) and 0.97 (0.93, 1.01), respectively. The maximum rise (R(max)) and maximum change (Delta(max)) were 1.04 (1.02, 1.05) and 1.00 (0.96, 1.03), respectively. All treatment-emergent and treatment-related adverse events were mild to moderate in severity. There were no obvious differences in adverse events according to treatment.


CONCLUSIONS
Warfarin pharmacokinetics/pharmacodynamics were not affected in subjects treated with warfarin 25mg who received cinacalcet 30 mg twice daily, thus suggesting that dose adjustment is not required.
Padhi
Desmond
D
Department of Early Development/Medical Sciences, Amgen Inc., Thousand Oaks, California 91320, USA. dpadhi@amfen.com
Sullivan
John T
JT
D000293:Adolescent; D000328:Adult; D000925:Anticoagulants / Q000009:adverse effects / Q000493:pharmacokinetics* / Q000494:pharmacology*; D019540:Area Under Curve; D000069449:Cinacalcet; D004311:Double-Blind Method; D004347:Drug Interactions; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D009281:Naphthalenes / Q000009:adverse effects / Q000494:pharmacology*; D011517:Prothrombin Time; D013237:Stereoisomerism; D014859:Warfarin / Q000009:adverse effects / Q000493:pharmacokinetics* / Q000494:pharmacology*
D000925:Anticoagulants; D009281:Naphthalenes; D014859:Warfarin; D000069449:Cinacalcet