section name header

Pronunciation

sil-DEN-a-fil

Classifications

Therapeutic Classification: erectile dysfunction agents, vasodilators

Pharmacologic Classification: phosphodiesterase type 5 inhibitors

Indications

REMS


Viagra

Revatio and Liqrev

Action

  • Viagra: Enhances effects of nitric oxide released during sexual stimulation. Nitric oxide activates guanylate cyclase, which produces increased levels of cyclic guanosine monophosphate (cGMP). cGMP produces smooth muscle relaxation of the corpus cavernosum, which promotes increased blood flow and subsequent erection. cGMP also leads to vasodilation of the pulmonary vasculature. Sildenafil inhibits the enzyme phosphodiesterase type 5 (PDE5), PDE5 inactivates cGMP.
  • Revatio and Liqrev: Produces vasodilation of the pulmonary vascular bed.
Therapeutic effects:
  • Viagra: Enhanced blood flow to the corpus cavernosum and erection sufficient to allow sexual intercourse.
  • Requires sexual stimulation.
  • Revatio and Liqrev: Improved exercise tolerance (or pulmonary hemodynamics) and delayed worsening of disease.

Pharmacokinetics

Absorption: Rapidly absorbed (41%) after oral administration; IV administration results in complete bioavailability.

Distribution: Widely distributed to tissues; negligible amount in semen.

Protein Binding: 96%.

Metabolism/Excretion: Primarily metabolized by the liver via the CYP3A4 isoenzyme; one metabolite is active and accounts for 20% or more of drug effect. Metabolites excreted mostly (80%) in feces; 13% excreted in urine.

Half-Life: 4 hr (for sildenafil and active metabolite).

Time/Action Profile

(vasodilation, ability to produce erection)

ROUTEONSETPEAKDURATION
POwithin 1 hr30–120 minup to 4 hr





Contraind./Precautions

Contraindicated in:

Use Cautiously in:

Adv. Reactions/Side Effects

CV: hypotension, MI, SUDDEN DEATH, vaso-occlusive crises

Derm: flushing, rash

EENT: epistaxis, hearing loss, nasal congestion, vision loss

GI: dyspepsia, diarrhea

GU: priapism, urinary tract infection

MS: myalgia

Neuro: headache, dizziness, insomnia, paresthesia

Misc: HYPERSENSITIVITY REACTIONS (INCLUDING ANAPHYLAXIS)

Interactions

Drug-drug:

Route/Dosage

Erectile Dysfunction

Pulmonary Arterial Hypertension

Availability

(Generic available)

Assessment

Implementation

IV Administration:

Patient/Family Teaching

Evaluation/Desired Outcomes

US Brand Names

Liqrev, Revatio, Viagra

Pill Image

sildenafil_-9192.jpg