Avanafil

7 DRUG INTERACTIONS • Avanafil can potentiate the hypotensive effect of nitrates, alpha-blockers, antihypertensives, and alcohol ( 7.1 ) • CYP3A4 inhibitors (e.g., ketoconazole, ritonavir, erythromycin) increase avanafil exposure ( 7.2 )

7.1 Potential for Pharmacodynamic Interactions with Avanafil Nitrates Administration of avanafil to patients who are using any form of organic nitrate, is contraindicated. In a clinical pharmacology trial, avanafil was shown to potentiate the hypotensive effect of nitrates. In a patient who has taken avanafil, where nitrate administration is deemed medically necessary in a life-threatening situation, at least 12 hours should elapse after the last dose of avanafil before nitrate administration is considered.

In such circumstances, nitrates should only be administered under close medical supervision with appropriate hemodynamic monitoring [see Contraindications ( 4.1 ), Dosage and Administration ( 2.3 ), and Clinical Pharmacology ( 12.2 )]. Alpha-Blockers Caution is advised when PDE5 inhibitors are co-administered with alpha-blockers. PDE5 inhibitors, including avanafil, and alpha-adrenergic blocking agents are both vasodilators with blood pressure-lowering effects. When vasodilators are used in combination, an additive effect on blood pressure may be anticipated.

In some patients, concomitant use of these two drug classes can lower blood pressure significantly leading to symptomatic hypotension (e.g., dizziness, lightheadedness, fainting) [see Warnings and Precautions ( 5.6 ), Dosage and Administration ( 2.3 ), and Clinical Pharmacology ( 12.2 )]. Antihypertensives PDE5 inhibitors, including avanafil, are mild systemic vasodilators. A clinical pharmacology trial was conducted to assess the effect of avanafil on the potentiation of the blood pressure-lowering effects of selected antihypertensive medications (amlodipine and enalapril).

Additional reductions in blood pressure of 3 to 5 mmHg occurred following co-administration of a single 200 mg dose of avanafil with these agents compared with placebo [see Warnings and Precautions ( 5.6 ) and Clinical Pharmacology ( 12.2 )]. Alcohol Both alcohol and PDE5 inhibitors, including avanafil, act as vasodilators. When vasodilators are taken in combination, blood pressure-lowering effects of each individual compound may be increased.

Substantial consumption of alcohol (e.g., greater than 3 units) in combination with avanafil can increase the potential for orthostatic signs and symptoms, including increase in heart rate, decrease in standing blood pressure, dizziness, and headache [see Clinical Pharmacology ( 12.2 )].

7.2 Potential for Other Drugs to Affect Avanafil Avanafil is a substrate of and predominantly metabolized by CYP3A4. Studies have shown that drugs that inhibit CYP3A4 can increase avanafil exposure. Strong CYP3A4 Inhibitors Ketoconazole (400 mg daily), a selective and strong inhibitor of CYP3A4, increased avanafil 50 mg single-dose systemic exposure (AUC) and maximum concentration (C max) equal to 13-fold and 3-fold, respectively, and prolonged the half-life of avanafil to approximately 9 hours.

Other potent inhibitors of CYP3A4 (e.g., itraconazole, clarithromycin, nefazadone, ritonavir, saquinavir, nelfinavir, indinavir, atanazavir and telithromycin) would be expected to have similar effects. Do not use avanafil in patients taking strong CYP3A4 inhibitors [see Warnings and Precautions ( 5.2 ) and Dosage and Administration ( 2.3 )]. HIV Protease inhibitor — Ritonavir (600 mg twice daily), a strong CYP3A4 inhibitor, which also inhibits CYP2C9, increased avanafil 50 mg single-dose C max and AUC equal to approximately 2-fold and 13-fold, and prolonged the half-life of avanafil to approximately 9 hours in healthy volunteers. Do not use avanafil in patients taking ritonavir.

Moderate CYP3A4 Inhibitors Erythromycin (500 mg twice daily) increased avanafil 200 mg single-dose C max and AUC equal to approximately 2-fold and 3-fold, respectively, and prolonged the half-life of avanafil to approximately 8 hours in healthy volunteers. Moderate CYP3A4 inhibitors (e.g., erythromycin, amprenavir, aprepitant, diltiazem, fluconazole, fosamprenavir, and verapamil) would be expected to have similar effects. Consequently, the maximum recommended dose of avanafil is 50 mg, not to exceed once every 24 hours for patients taking concomitant moderate CYP3A4 inhibitors [see Warnings and Precautions ( 5.2 ) and Drug Interactions ( 7.2 )].

Although specific interactions have not been studied, other CYP3A4 inhibitors, including grapefruit juice are likely to increase avanafil exposure. Weak CYP3A4 Inhibitors No in vivo drug-drug interaction studies with weak CYP3A4 inhibitors were conducted. CYP3A4 Substrate When administered with avanafil 200 mg, amlodipine (5 mg daily) increased the C max and AUC of avanafil by approximately 22% and 70%, respectively. The half-life of avanafil was prolonged to approximately 10 hrs. The C max and AUC of amlodipine decreased by approximately 9% and 4%, respectively [see Dosage and Administration ( 2.3 )].

Cytochrome P450 Inducers The potential effect of CYP inducers on the pharmacokinetics of avanafil was not evaluated. The concomitant use of avanafil and CYP inducers is not recommended.

8.1 Pregnancy Risk Summary Avanafil is not indicated for use in females. There are no data with the use of avanafil in pregnant women to inform any drug-associated risks for adverse developmental outcomes. In animal reproduction studies conducted in pregnant rats and rabbits, no adverse developmental outcomes were observed with oral administration of avanafil during organogenesis at exposures for total avanafil at approximately 8 and 6 times, respectively, the Maximum Recommended Human Dose (MRHD) of 200 mg based on AUC (see Data).

Data Animal Data In pregnant rats administered orally at 100, 300, or 1000 mg/kg/day from gestation days 6 to 17, no evidence of teratogenicity, embryotoxicity, or fetotoxicity was observed at up to 300 mg/kg/day. This dose is equivalent to exposures of approximately 8 times the exposure at the Maximum Recommended Human Dose (MRHD) of 200 mg based on AUCs for total avanafil. At the maternally toxic dose (1000 mg/kg/day), decreased fetal body weight occurred with no signs of teratogenicity.

In pregnant rabbits administered orally at 30, 60, 120, or 240 mg/kg/day from gestation days 6 to 18, no teratogenicity was observed at exposures up to approximately 6 times the human exposure at the MRHD based on AUCs for total avanafil. In a pre- and post-natal development study in rats given orally at 100, 300, or 600 mg/kg/day on gestation days 6 through lactation day 20, offspring growth and maturation were reduced when maternal rats were given avanafil doses greater than or equal to 300 mg/kg/day, resulting in exposures greater than or equal to 17 times the human exposure to total avanafil at the MRHD.

There was no effect on reproductive performance of the maternal rats or offspring, or on the behavior of the offspring at up to the highest dose tested. The no observed adverse effect level (NOAEL) for developmental toxicity (100 mg/kg/day) was observed at exposures to total avanafil approximately 2-fold greater than the systemic exposure in humans at the MRHD.

8.3 Females and Males of Reproductive Potential Infertility There have been no studies evaluating the effect of avanafil on fertility in men [see Clinical Pharmacology ( 12.2 )] Based on studies in animals, decreased fertility, abnormal sperm motility and morphology, and altered estrous cycles were observed in rats. The abnormal sperm findings were reversible at the end of a 9-week drug-free period [see Nonclinical Toxicology ( 13.1 )].