Systemic absorption after intravaginal propranolol

Bioavailability of propranolol following oral and transdermal administration in rabbits

The systemic bioavailability of propranolol was evaluated following oral and transdermal administration in rabbits. Using a four-way crossover study, the bioavailability of propranolol following oral administration was determined to be 12.3 +/- 5.9%, indicating that propranolol is subject to extensive hepatic first-pass metabolism in rabbits. Transdermal delivery of propranolol, via an adhesive delivery device, resulted in a bioavailability of 74.8 +/- 10.1%, indicating that the transdermal delivery of propranolol can significantly increase systemic bioavailability over oral administration. Skin irritation studies indicated that neither propranolol nor the adhesive used in the device caused any appreciable skin irritation.

A comparative study of the pharmacokinetics of propranolol and its major metabolites in the rat after oral and vaginal administration

1. The concentrations of propranolol (PPL) and its metabolites were monitored by h.p.l.c. in serum of rats during the first 6 h after administering single doses (20 mg/kg) of PPL either orally or intravaginally (i.vg). 2. The results showed that PPL was quickly transferred to the systemic circulation from the rat vagina and the serum concentration profile as substantially altered by the route of administration. Serum concentrations of free PPL were significantly higher in i.vg-dosed animals than their oral dosed counterparts. 3. Inter-animal serum conc. variations of PPL and its metabolites in the i.vg-dosed rats were smaller than those of the orally treated females. 4. In comparison with the i.vg-dosed rats, the levels of PPL metabolites (propranolol glycol, naphthoxylactic acid, naphthoxyacetic acid) were greater by the oral route, though these differences were not statistically significant. 5. The serum elimination half-lives (t1/2)beta of PPL and its metabolites during the beta-phase were not significantly different in the two treatment groups. 6. Following i.vg application, both the AUC and the Cmax values of PPL were significantly greater than those of orally dosed females, while no statistically significant differences were found in the tmax values. 7. Comparison of the AUC values showed that relative bioavailability of PPL was approx. 36 times greater in i.vg-treated animals than those of the orally dosed rats.

Recent observations on drugs and human fertility

The transmembrane migration method has permitted quantification of the effect of drugs on human sperm motility. Calcium ionophores and calcium antagonists have paradoxical effects on motility depending on the stage of sperm maturity. Drugs with membrane stabilizing properties inhibit sperm motility. Propranolol, for example, has been shown to have contraceptive activity when administered intra-vaginally. Pharmacokinetic studies have shown that the systemic availability of vaginally administered propranolol is markedly greater than after oral administration. Seminal fluid concentrations of propranolol after oral administration are similar to those in plasma, but cervicovaginal mucus concentrations are much higher, and residence times much longer. The clinical consequences of these observations await elucidation.

Transplacental and mammary passage of radioactivity in rats treated vaginally and orally with [14C]propranolol

The milk transfer, maternal-fetal distribution, and disposition of the antihypertensive/spermicidal agent propranolol were studied in pregnant and lactating rats. Single doses (10 mg/kg) of an aqueous solution of [14C]propranolol were administered either orally (po) or intravaginally (ivg) on gestational d 15, or on postpartum d 7-10. Upon ivg administration, [14C]propranolol was quickly transferred to systemic circulation and the mean blood [14C] concentrations were significantly greater during the first 0.25-2 h than in po dosed counterparts. About 98% of the ivg applied dose was absorbed after 6 h in gravid rats, and the combined 6-h excretions of radioactivity in the urine (ivg = 24.6%; po = 22.9%) and feces (ivg = 16.8%; po = 14.6%) were equivalent in both groups. At the end of 6 h, the levels of [14C] in the urinary bladder, adrenal, uterus, ovary, spleen, skeletal muscle, brain, heart, lung and fat were significantly higher in ivg treated rats than po dosed animals. Compared with the maternal plasma (ivg = 0.76; po = 0.88 microgram/ml), the mean concentrations of [14C] in the placentas were similar in both groups, while the amounts of [14C] were three to five times lower in the amniotic fluids and the fetuses of both po and ivg treated dams. In lactating rats, over 99% of the administered radioactivity was absorbed from the vagina within 6 h. The blood concentrations of [14C] were significantly elevated at 0.5 and 1 h in the per vaginam treated animals, and afterward the disappearance rate of [14C] followed a similar course in both groups. Following ivg application, the milk radioactivity peaked at 0.5 h and declined rapidly. However, the appearance of [14C] in milk was rather slow after oral dosing: the milk [14C] peaked between 2 and 3 h posttreatment and remained steady thereafter. The milk to blood (M/B) [14C] concentration ratios were markedly greater during 0.5 to 1 h in the ivg group than in their po dosed counterparts. At 6 h, the [14C] levels in the whole blood, plasma, milk, and mammary gland were virtually equivalent in the ivg and po treated females. Comparison of the areas under the milk [14C] concentration-time curves (AUCs) indicated that the milk availability of [14C] was about 31% more in dams dosed vaginally. These data suggest that route of administration alters the disposition and milk excretion of [14C]propranolol-derived radioactivity in pregnant and lactating rats.

Vaginal absorption of naproxen

The vaginal absorption of the drug naproxen was investigated in five healthy pre-menopausal women. It was found that naproxen was absorbed, but not to therapeutically useful levels.