Pharmacodynamics

Combination oral contraceptives (COCs) act by suppression of gonadotropins. Although the primary mechanism of this action is inhibition of ovulation, other alterations include changes in the cervical mucus (which increases the difficulty of sperm entry into the uterus) and the endometrium (which reduces the likelihood of implantation).

Drospirenone is a spironolactone analogue with antimineralocorticoid activity. Preclinical studies in animals and in vitro have shown that drospirenone has no androgenic, estrogenic, glucocorticoid, and antiglucocorticoid activity. Preclinical studies in animals have also shown that drospirenone has antiandrogenic activity.

Pharmacokinetics

Absorption

The absolute bioavailability of drospirenone (DRSP) from a single entity tablet is about 76%. The absolute bioavailability of ethinyl estradiol (EE) is approximately 40% as a result of presystemic conjugation and first-pass metabolism. The absolute bioavailability of YASMIN which is a combination tablet of drospirenone and ethinyl estradiol has not been evaluated. Serum concentrations of DRSP and EE reached peak levels within 1-3 hours after administration of YASMIN. After single dose administration of YASMIN, the relative bioavailability, compared to a suspension, was 107% and 117% for DRSP and EE, respectively.

The pharmacokinetics of DRSP are dose proportional following single doses ranging from 1-10 mg. Following daily dosing of YASMIN, steady state DRSP concentrations were observed after 10 days. There was about 2 to 3 fold accumulation in serum Cmax and AUC (0-24h) values of DRSP following multiple dose administration of YASMIN (see Table I).

For EE, steady-state conditions are reported during the second half of a treatment cycle. Following daily administration of YASMIN serum Cmax and AUC (0-24h) values of EE accumulate by a factor of about 1.5 to 2.0.

TABLE OF MEAN PHARMACOKINETIC PARAMETERS OF YASMIN
(Drospirenone 3 mg and Ethinyl Estradiol 0.030 mg )
TABLE I

Effect of Food

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