Pharmacokinetics of progesterone after its administration to ovariectomized rhesus monkeys by injection, infusion, or nasal spraying.

The pharmacokinetics of progesterone (dose: 10 microgram per animal) were studied in blood and cerebrospinal fluid of adult ovariectomized rhesus monkeys after the administration of the steroid as an intravenous injection, intravenous infusion (duration of infusion: 10 min), or nasal spray. The bioavailability of progesterone, in terms of area under the time--concentration curve and the maximal concentration in the two body fluids, was significantly higher when the steroid was infused or sprayed intranasally than when it was injected intravenously. The clearance of the steroid from the serum, as estimated by its elimination rate constant, elimination half-life, and total body clearance, did not differ for the three methods of administration. These findings suggest that the bioavailability of progesterone is enhanced by extending the duration over which the steroid is delivered into the hemic circulation.