Avanafil 50 mg · Tablets

The physiologic mechanism of erection of the penis involves release of nitric oxide (NO) in the corpus cavernosum during sexual stimulation. NO then activates the enzyme guanylate cyclase, which results in increased levels of cGMP, producing smooth muscle relaxation in the corpus cavernosum and allowing inflow of blood. Avanafil has no direct relaxant effect on isolated human corpus cavernosum, but enhances the effect of NO by inhibiting PDE5, which is responsible for degradation of cGMP in the corpus cavernosum. Because sexual stimulation is required to initiate the local release of nitric oxide, the inhibition of PDE5 has no effect in the absence of sexual stimulation.

Studies in vitrohave shown that avanafil is selective for PDE5. Its effect is more potent on PDE5 than on other known phosphodiesterases (greater than 100-fold for PDE6; greater than 1,000-fold for PDE4, PDE8 and PDE10; greater than 5,000-fold for PDE2 and PDE7; greater than 10,000-fold for PDE1, PDE3, PDE9, and PDE11). Avanafil is greater than 100-fold more potent for PDE5 than PDE6, which is found in the retina and is responsible for phototransduction. In addition to human corpus cavernosum smooth muscle, PDE5 is also found in other tissues including platelets, vascular and visceral smooth muscle, and skeletal muscle, brain, heart, liver, kidney, lung, pancreas, prostate, bladder, testis, and seminal vesicle. The inhibition of PDE5 in these tissues by avanafil may be the basis for the enhanced platelet anti-aggregatory activity of NO observed in vitroand peripheral vasodilatation in vivo.

Mean avanafil plasma concentrations measured after the administration of a single oral dose of 50 or 200 mg to healthy male volunteers are depicted in Figure 4. The pharmacokinetics of avanafil are dose proportional from 12.5 to 600 mg.

Absorption and Distribution — Avanafil is rapidly absorbed after oral administration, with a median T maxof 30 to 45 minutes in the fasted state. When avanafil (200 mg) is taken with a high fat meal, the rate of absorption is reduced, with a mean delay in T maxof 1.12 to 1.25 hours and a mean reduction in C maxof 39% (200 mg). There was an approximate 3.8% decrease in AUC. The small changes in avanafil C maxand AUC are considered of minimal clinical significance; therefore, avanafil may be administered with or without food. The mean accumulation ratio is approximately 1.2. Avanafil is approximately 99% bound to plasma proteins. Protein binding is independent of total drug concentrations, age, renal and hepatic function.

Based upon measurements of avanafil in semen of healthy volunteers 45 to 90 minutes after dosing, less than 0.0002% of the administered dose appeared in the semen of patients.

Metabolism and Excretion — Avanafil is cleared predominantly by hepatic metabolism, mainly by the CYP3A4 enzyme and to a minor extent by CYP2C isoform. The plasma concentrations of the major circulating metabolites, M4 and M16, are approximately 23% and 29% that of the parent compound, respectively. The M4 metabolite has an in vitroinhibitory potency for PDE5 18% of that of avanafil and M4 accounts for approximately 4% of the pharmacologic activity of avanafil. The M16 metabolite was inactive against PDE5.

Avanafil was extensively metabolized in humans. After oral administration, avanafil is excreted as metabolites predominantly in the feces (approximately 62% of administered oral dose) and to a lesser extent in the urine (approximately 21% of the administered oral dose). Avanafil has a terminal elimination half-life of approximately 5 hours.

Geriatric — The pharmacokinetics of a single 200 mg avanafil administered to fourteen healthy elderly male volunteers (65 to 80 years) and eighteen healthy younger male volunteers (18 to 43 years of age) were compared. AUC 0 to infincreased by 6.8% and C maxdecreased by 2.1% in the elderly group, compared to the younger group. However, greater sensitivity to medications in some older individuals should be considered [see Use in Specific Populations ( 8.5)].

Renal Impairment — The pharmacokinetics of a single 200 mg avanafil administered to nine patients with mild (creatinine clearance greater than or equal to 60 and less than 90 mL/min) and to ten patients with moderate (creatinine clearance greater than or equal to 30 to less than 60 mL/min) renal impairment were evaluated. AUC 0-infdecreased by 2.9% and C maxincreased by 2.8% in patients with mild renal impairment, compared to healthy volunteers with normal renal function. AUC 0-infincreased by 9.1% and C maxdecreased by 2.8% in patients with moderate renal impairment, compared to healthy volunteers with normal renal function. There is no data available for subjects with severe renal insufficiency or end-stage renal disease on hemodialysis [see Use in Specific Populations ( 8.6)].

Hepatic Impairment — The pharmacokinetics of a single 200 mg avanafil administered to eight patients with mild hepatic impairment (Child-Pugh A) and eight patients with moderate hepatic impairment (Child-Pugh B) were evaluated. AUC 0-infincreased by 3.8% and C maxdecreased by 2.7% in patients with mild hepatic impairment, compared to healthy volunteers with normal hepatic function. AUC 0-infincreased by 11.2% and C maxdecreased by 51% in patients with moderate hepatic impairment, compared to healthy volunteers with normal hepatic function. There is no data available for subjects with severe hepatic impairment (Child-Pugh Class C) [see Use in Specific Populations ( 8.7)].