The pharmacokinetics of FIRAZYR has been characterized in studies using both intravenous and subcutaneous administration to healthy subjects and patients. The pharmacokinetic profile of FIRAZYR in patients with HAE is similar to that in healthy subjects.

The absolute bioavailability of FIRAZYR following a 30 mg subcutaneous dose is approximately 97%. Following subcutaneous administration of a single 30 mg dose of FIRAZYR to healthy subjects (N=96), a mean (± standard deviation) maximum plasma concentration (Cmax) of 974 ± 280 ng/mL was observed after approximately 0.75 hours. The mean area under the concentration-time curve (AUC0-∞) after a single 30 mg dose was 2165 ± 568 ng∙hr/mL, with no evidence of accumulation of icatibant following three 30 mg doses administered 6 hours apart. Following subcutaneous administration, plasma clearance was 245 ± 58 mL/min with a mean elimination half-life of 1.4 ± 0.4 hours and volume of distribution at steady state (Vss) of 29.0 ± 8.7 L.

Icatibant is extensively metabolized by proteolytic enzymes to inactive metabolites that are primarily excreted in the urine, with less than 10% of the dose eliminated as unchanged drug. Icatibant is not degraded by oxidative metabolic pathways, is not an inhibitor of major cytochrome P450 (CYP) isoenzymes (CYP 1A2, 2A6, 2B6, 2C8, 2C9, 2C19, 2D6, 2E1, and 3A4) and is not an inducer of CYP 1A2 and 3A4.

Special populations

Hepatic Impairment

The pharmacokinetic parameters of FIRAZYR were found to be generally comparable between healthy subjects (n=8) and mild to moderate (Child Pugh scores of 5 to 8) hepatic impaired patients (n=8) following a dose of 0.15 mg/kg/day as continuous intravenous infusion over 3 days. In a separate study, FIRAZYR clearance in subjects with a wide range of hepatic impairment (Child-Pugh scores of 7 to 15) was similar to that in healthy subjects. No dose adjustment is necessary for patients with impairment of hepatic function [see Use in Specific Populations (8.6)].

Renal Impairment

Since renal clearance of icatibant is a minor eliminating pathway, renal impairment is not expected to affect the pharmacokinetics of FIRAZYR and hence a formal renal impairment study was not conducted for FIRAZYR. In 10 patients with hepatorenal syndrome (GFR 30-60 mL/min), clearance of FIRAZYR was not dependent on renal function and therefore, did not show any observable differences in the plasma levels of icatibant or its metabolites compared to subjects with normal renal function. No dose adjustment is necessary for patients with impairment of renal function [see Use in Specific Populations (8.7)].

Age and Gender

Three 30 mg subcutaneous doses of FIRAZYR administered every 6 hours were studied in young (18 to 45 years of age) and elderly (over 65 years of age) healthy male and female subjects. Following single-dose administration of 30 mg subcutaneous FIRAZYR, elderly males and females showed approximately 2-fold higher AUC compared to young males and females, respectively. However, only minor differences (~12-14%) between Cmax of gender–matched elderly and young subjects were observed. Older subjects tend to exhibit lower clearance compared to younger subjects and therefore higher systemic exposure. Gender effect on FIRAZYR pharmacokinetics was also observed in addition to age effect. Clearance of FIRAZYR is significantly correlated with bodyweight with lower clearance values noted for lower bodyweights. Hence, females with typically lower body weights compared to males exhibit lower clearance values, resulting in approximately 2-fold higher systemic exposure (both AUC and Cmax) compared to males. Differences in efficacy and safety between elderly and younger patients and male and female patients have not been identified. Dose adjustment based on age and gender is not warranted.

Drug Interactions

Formal drug-drug interaction studies were not conducted with FIRAZYR. Icatibant metabolism is not mediated by CYP450 enzymes. In vitro study did not show any significant inhibition and/or induction of drug metabolizing CYP450 enzymes; therefore, metabolic drug interactions between FIRAZYR and CYP450 substrates, inhibitors and inducers are not expected.