What questions should be asked before prescribing Viagra (sildenafil) to a patient with a history of cardiovascular disease, diabetes, and potential interactions with nitrates, alpha-blockers, and other medications?

Pre-Prescribing Assessment for Viagra (Sildenafil)

Before prescribing Viagra, you must explicitly ask about nitrate use in any form—this is an absolute contraindication that can cause fatal hypotension. 1, 2, 3

Critical Safety Questions (Absolute Contraindications)

Nitrate Use - Ask Specifically About:

• Prescription nitrates: nitroglycerin (tablets, patches, sprays, ointments), isosorbide mononitrate, isosorbide dinitrate 3
• Recreational drugs: "poppers" (amyl nitrate or nitrite) 3
• Any chest pain medications the patient may use as needed 1

If the patient takes nitrates in any form, Viagra is absolutely contraindicated. If emergency nitrate administration becomes necessary after sildenafil use, wait at least 24 hours under close medical supervision. 1, 2

Cardiovascular Risk Stratification

Ask the patient: "Can you walk 1 mile in 20 minutes or climb 2 flights of stairs without chest pain, severe shortness of breath, or other symptoms?" 1, 2

• If YES: Patient is likely low-risk and can safely use Viagra 1
• If NO or UNCERTAIN: Refer to cardiology before prescribing 1, 2

High-Risk Cardiovascular Conditions (Defer Treatment Until Stabilized):

• Unstable or refractory angina 1, 2
• Uncontrolled hypertension 1, 2
• Recent myocardial infarction or stroke (within 2 weeks) 1, 2
• Severe heart failure (NYHA class II or higher) 1, 2
• Hypotension (systolic BP <100 mmHg) 2
• Recent stroke 1, 2

These patients should have their cardiac condition stabilized before considering ED treatment. 1, 2

Medication History Questions

Alpha-Blockers

• Ask: "Are you taking any medications for prostate problems or blood pressure like tamsulosin, doxazosin, or terazosin?" 1
• Alpha-blockers can cause additive blood pressure lowering but are not contraindicated—just monitor for symptomatic hypotension 4

CYP3A4 Inhibitors (Require Lower Starting Dose of 25mg)

• Ritonavir or other HIV medications 2, 3
• Ketoconazole or itraconazole (antifungals) 2
• Erythromycin (antibiotic) 2
• Cimetidine (H2-blocker) 2

These medications increase sildenafil levels and require starting at 25mg instead of 50mg. 2

Other Antihypertensive Medications

• Beta-blockers, ACE inhibitors, calcium channel blockers, and diuretics cause additive (not potentiating) blood pressure decreases and are generally safe to use with sildenafil 4

Medical History Questions

Hepatic and Renal Function

• Severe hepatic impairment: Contraindication or requires 25mg starting dose 1, 2
• Renal impairment: Requires 25mg starting dose 2

Diabetes Status

• Ask about diabetes: Patients with diabetes have more severe baseline ED and may respond less robustly to PDE5 inhibitors, but sildenafil remains effective 2
• Diabetes screening is recommended as basic investigation before ED treatment 1

Testosterone Deficiency

• Ask about: Low libido, fatigue, decreased energy 1
• Consider checking testosterone levels, especially if there are signs of hypogonadism 1, 2
• Low testosterone (<300 ng/dL) may require combination therapy with testosterone replacement for optimal results 2

Ophthalmologic History

• Hereditary degenerative retinal disorders (e.g., retinitis pigmentosa) 1, 3
• History of sudden vision loss or non-arteritic anterior ischemic optic neuropathy (NAION) 3

Hematologic Conditions

• Sickle cell anemia, leukemia, multiple myeloma (increased risk of priapism) 3
• Bleeding disorders 1

Anatomic Penile Problems

• Peyronie's disease or other penile deformities 3

Patient Education and Expectations

Proper Use Instructions (Common Cause of "Treatment Failure")

• Sexual stimulation is mandatory for sildenafil to work—it is not an aphrodisiac 2, 5
• Timing: Take approximately 1 hour before sexual activity 2
• Food interactions: Avoid taking with large/high-fat meals, which delay absorption 2
• Alcohol: Heavy alcohol use impairs erectile function and should be avoided 2

Adequate Trial Definition

• At least 5 separate attempts at maximum tolerated dose before declaring treatment failure 2
• Many "failures" result from inadequate sexual stimulation, improper timing, or heavy alcohol use rather than true medication ineffectiveness 2

Dosing Strategy

Starting Dose

• Standard: 50mg, taken 1 hour before sexual activity 2
• Lower dose (25mg) required for: severe hepatic impairment, renal impairment, age >65, or concurrent CYP3A4 inhibitors 2

Dose Titration

• If 50mg inadequate: Increase to 100mg (maximum dose) 2
• If 50mg causes intolerable side effects: Decrease to 25mg 2

Common Pitfalls to Avoid

1. Not asking specifically about all forms of nitrate use (including recreational "poppers") 3
2. Failing to assess cardiovascular fitness before prescribing 1, 2
3. Declaring treatment failure without ensuring proper use: adequate sexual stimulation, correct timing, avoidance of heavy meals/alcohol, and at least 5 attempts at maximum dose 2
4. Not checking for CYP3A4 inhibitors that require dose adjustment 2
5. Forgetting that testosterone deficiency reduces PDE5 inhibitor response—consider checking levels if clinical suspicion exists 2