Drospirenone

When ATH:
G03AA12

Pharmacological action.

After oral administration drospirenone is rapidly and completely absorbed. The maximum concentration in serum is 37 ng / ml, It reached approximately 1-2 hours after a single oral dose. Bioavailability - about 76-85%. Simultaneous food intake has no effect on the bioavailability of the drug.

Drospirenone binds to plasma albumin, It is not bound to SHBG and SHBG. Only 3-5% of the total amount of serum is idle, 95-97% Non-specifically bound to albumin. Ethinylestradiol-induced increase of SHBG not affect the binding of drospirenone with plasma proteins. The average volume of distribution of drospirenone is 3.7-4.2 l / kg.

Drospirenone completely metabolized. The major metabolites in plasma are the acid forms of drospirenone, which are formed by opening the lactone ring, and 4,5-dihydro-drospirenone-3-sulfate. Both metabolites are formed without the involvement of P450.

The small amount of drospirenone metabolized by cytochrome P450 ZA4 (данные in vitro). Clearance rate of drospirenone in serum of about 1.2-1.5 ml / min / kg. Direct interaction of drospirenone and ethinyl estradiol were found.

Concentration drospirenone in serum decreased in the two phases. In the terminal phase half-life is about 31 no. Drospirenone is output unchanged. The metabolites are excreted in the urine and bile in the ratio of 1,2 to 1,4; half-life is about 1,7 day.

On the pharmacokinetics of drospirenone does not affect the concentration of SHBG. After daily administration of the drug concentration in blood serum increases by 2-3 times, reaching equilibrium concentration in the second half cycle of reception.