for Health Care Providers

Table 2. Potential ARV Interactions (ED)

Recommended Dosing of PDE5 Inhibitors
Serum levels of all PDE5 inhibitors are significantly increased in the presence of CYP 3A4 inhibitors such as PIs. See Recommended Dosing below.
PDE5 Inhibitor	Dosing Instructions	Patients on PIs and Other Strong CYP 3A4 Inhibitors	Patients Not on Interacting Drugs
Vardenafil (Levitra)	Take on empty stomach 1 hour before sexual activity	Start: 2.5 mg per 72 hours Maximum: 5 mg per 72 hrs	Start: 2.5-10 mg per day (≤5 mg if age >65) Maximum: 20 mg every 24 hours
Sildenafil (Viagra)	Take on empty stomach 0.5-4 hours before sexual activity	Start: 25 mg per day Maximum: 25 mg every 48 hours	Start: 25-50 mg per day (25 mg if age >65) Maximum: 100 mg every 24 hours
Tadalafil (Cialis)	Take with or without food, before sexual activity	5 mg per day Maximum: 10 mg every 72 hours	Start: 5-10 mg per day Maximum: 10 mg every 72 hours

From Urology
Primary Care of Veterans with HIV
Office of Clinical Public Health Programs
Veterans Health Administration, 2009