PDE-5 inhibitors
Nursing pharmacology study reference (NCLEX-style monograph). Numeric values are standard teaching ranges for study and must be verified against current manufacturer labeling before clinical use. This is educational content, not prescribing guidance.
PDE-5 inhibitors (brand names Viagra, Revatio, Cialis, Adcirca) — Erectile dysfunction agent, pulmonary hypertension agent, benign prostatic hyperplasia (tadalafil); Phosphodiesterase-5 inhibitors.
Identification
- Therapeutic class: Erectile dysfunction agent, pulmonary hypertension agent, benign prostatic hyperplasia (tadalafil).
- Pharmacologic class: Phosphodiesterase-5 inhibitors.
Pharmacology
- Mechanism of action: Inhibit PDE-5 to enhance nitric oxide-mediated vasodilation in the penis and pulmonary vasculature.
- Onset / peak / duration: Sildenafil onset 30 to 60 minutes; tadalafil longer acting (up to 36 hours).
- Half-life / therapeutic level: Sildenafil about 4 hours, tadalafil about 17.5 hours; no routine level.
Clinical use
- Indications: Erectile dysfunction, pulmonary arterial hypertension, benign prostatic hyperplasia (tadalafil).
- Usual dose, route, frequency: PO as needed before activity (erectile dysfunction) or daily (pulmonary hypertension, BPH).
- Maximum dose / adjustments: Reduce with strong CYP3A4 inhibitors and in hepatic or renal impairment; lower doses with alpha blockers.
Safety
- Contraindications: Concurrent nitrates in any form, recent severe cardiovascular event, severe hypotension.
- Black box warning: None.
- Interactions: Nitrates (life-threatening hypotension, absolute contraindication), alpha blockers (hypotension), CYP3A4 inhibitors, riociguat.
- Pregnancy / lactation: Pulmonary hypertension use case by case.
- High-alert: No.
Adverse effects
- Common side effects: Headache, flushing, nasal congestion, dyspepsia, visual color changes.
- Serious effects to report: Priapism (erection over 4 hours, an emergency), sudden vision loss (NAION), sudden hearing loss, severe hypotension.
- Antidote / reversal: Supportive care.
Nursing process
- Assessment before administration: Cardiovascular status, nitrate use, blood pressure.
- Interventions during therapy: Confirm no nitrate use; counsel on priapism.
- Monitor: Blood pressure, response, vision and hearing changes.
- Evaluation / expected outcome: Improved erectile function or pulmonary pressures.
Patient teaching
- Patient teaching: Never combine with nitrates or recreational nitrites (poppers); seek emergency care for an erection lasting over 4 hours or sudden vision or hearing loss.
- Notify provider if: Erection over 4 hours, sudden vision or hearing change, chest pain.
- Administration tips: Take before activity (erectile dysfunction); avoid high-fat meals with sildenafil (delays onset).