COMMON INITIAL DOSING REGIMENS

• For Erectile Dysfunction: The initial dose is typically 50 mg taken approximately one hour before sexual activity. The dose may be adjusted to 25 mg or 100 mg based on efficacy and tolerability. A maximum dosing frequency of once daily is recommended.

MECHANISM OF ACTION

• Sildenafil is a selective phosphodiesterase type 5 (PDE5) inhibitor. By inhibiting PDE5, it prevents the degradation of cyclic guanosine monophosphate (cGMP) in the smooth muscle cells of the corpus cavernosum and pulmonary vasculature.

• For erectile dysfunction, increased cGMP levels lead to smooth muscle relaxation and vasodilation, enhancing blood flow to the penis during sexual stimulation and facilitating erection.

COMMON SIDE EFFECTS

• Cardiovascular: Headache, flushing, and dizziness are common due to systemic vasodilation. Hypotension, tachycardia, and palpitations may also occur, particularly when combined with other vasodilators.

• Ophthalmologic: Visual disturbances, such as bluish vision (cyanopsia), increased light sensitivity, or blurred vision, occur due to inhibition of PDE6 in the retina.

• Gastrointestinal: Dyspepsia, nausea, and diarrhea.

• Respiratory: Nasal congestion and epistaxis.

• Rare but Severe: Non-arteritic anterior ischemic optic neuropathy (NAION), sudden hearing loss, or priapism (prolonged erection requiring medical attention).

CONTRAINDICATIONS

• Absolute: Concomitant use with nitrates (e.g., nitroglycerin) or guanylate cyclase stimulators (e.g., riociguat) due to the risk of severe hypotension. Hypersensitivity to sildenafil or any excipient.

• Relative: Use cautiously in individuals with severe cardiovascular disease, significant hypotension (<90/50 mmHg), recent history of stroke or myocardial infarction, or severe hepatic impairment. Patients with retinitis pigmentosa or predisposition to priapism (e.g., sickle cell anemia, multiple myeloma, leukemia) require additional monitoring.

ADDITIONAL NOTES ON EFFICACY

• Topical finasteride has been shown to reduce DHT levels in the scalp effectively while maintaining near-normal systemic DHT levels, thus lowering the risk of systemic side effects. Combining topical finasteride with minoxidil can enhance hair regrowth outcomes. Clinical response typically begins after 3–6 months of consistent application.

MORE INFORMATION

• FDA Safety Data Sheet for oral sildenafil may be found here.

• Goldstein I. The Serendipitous Story of Sildenafil: An Unexpected Oral Therapy for Erectile Dysfunction. Sex Med Rev. 2019 [PubMed Link]

• Fink HA. Sildenafil for male erectile dysfunction: a systematic review and meta-analysis. Arch Intern Med. 2002 [PubMed Link]

• Scaglione F. Phosphodiesterase Type 5 Inhibitors for the Treatment of Erectile Dysfunction: Pharmacology and Clinical Impact of the Sildenafil Citrate Orodispersible Tablet Formulation. Clin Ther. 2017 [PubMed Link]

• Licht MR. Use of oral sildenafil (Viagra) in the treatment of erectile dysfunction. Compr Ther. 1999 [PubMed Link]

• King R. Correlations between increased erection hardness and improvements in emotional well-being and satisfaction outcomes in men treated with sildenafil citrate for erectile dysfunction. Int J Impot Res. 2007 [PubMed Link]

• Goldstein I. Efficacy and Safety of Sildenafil by Age in Men With Erectile Dysfunction. J Sex Med. 2016 [PubMed Link]

• Moore RA. Sildenafil (Viagra) for male erectile dysfunction: a meta-analysis of clinical trial reports. BMC Urol. 2002 [PubMed Link]