Sildenafil

Intravenous
Pulmonary arterial hypertension

Oral
Erectile dysfunction

Oral
Pulmonary arterial hypertension

Patients on CYP3A4 inhibitors: Initially, not more than 25 mg daily.
Patients on ritonavir-boosted HIV inhibitors: Should not exceed 25 mg 48 hrly.
Patients stable on alpha-blockers: Initially, 25 mg.

Oral:
Erectile dysfunction:

CrCl (mL/min)	Dosage
<30	Initially, 25 mg.

Oral:
Pulmonary arterial hypertension:

CrCl (mL/min)	Dosage
<30	20 mg bid.

Intravenous:
Pulmonary arterial hypertension:

CrCl (mL/min)	Dosage
<30	10 mg bid.

Oral:
Erectile dysfunction: Mild or moderate: Initially, 25 mg. Severe: Contraindicated.
Pulmonary arterial hypertension: Mild or moderate: 20 mg bid. Severe: Contraindicated.

Intravenous:
Pulmonary arterial hypertension: Mild or moderate: 10 mg bid. Severe: Contraindicated.

May be taken with or without food.

Oral susp: Add a total of 90 mL of water in 2 portions, 60 mL for the 1st addition and 30 mL for the 2nd addition, to provide a susp containing 10 mg/mL. After each addition, cap and shake the bottle vigorously for at least 30 sec.

Patient w/ severe CV disorders (e.g. unstable angina, cardiac failure), loss of vision in 1 eye because of non-arteritic anterior ischaemic optic neuropathy (NAION), hypotension (BP <90/50 mmHg), recent history of stroke or MI, known hereditary degenerative retinal disorders. Severe hepatic impairment. Concomitant use w/ nitrates of any form and nicorandil.

Patient w/ anatomical deformation of the penis or haematological disorders that may predispose to priapism. Not indicated for pulmonary HTN secondary to sickle-cell disease. Mild to moderate hepatic and severe renal impairment. Childn (chronic use). Pregnancy and lactation.

Headache, flushing, dyspepsia, visual disturbances (e.g. blurred vision, photophobia, chromatopsia, cyanopsia, eye irritation, eye pain and redness); dizziness, insomnia, anxiety, vertigo, epistaxis, nasal congestion, pyrexia, GI disturbances (e.g. diarrhoea, vomiting), priapism; skin rashes, erythema, alopecia, limb/back pain, myalgia, facial oedema, fluid retention, paraesthesia, UTI, dyspnoea, cough, rhinitis, sinusitis, bronchitis, cellulitis, sudden decrease or loss of hearing, anaemia, leucopenia, gynaecomastia, urinary frequency or incontinence, haematuria, seizures, cerebrovascular haemorrhage, transient ischaemic attack, palpitations, syncope, HTN, hypotension. Rarely, hypersensitivity reactions, NAION causing permanent loss of vision, retinal haemorrhage.
Potentially Fatal: Serious CV events (e.g. MI, arrhythmias, tachycardia, unstable angina). 

IV/PO: B

This drug may cause dizziness and altered vision, if affected, do not drive or operate machinery. Seek medical assistance in cases of prolonged erection (>4 hr) or sudden visual or hearing loss.

Monitor BP and pulse when used concurrently w/ hypotensive drugs in the treatment of pulmonary arterial HTN.

Symptoms: Hypotension, syncope, prolonged erection. Management: Supportive treatment. For severe hypotension, may consider placing the patient in the Trendelenburg position, initiating fluid resuscitation, providing judicious use of an IV α-adrenergic agonist (e.g. phenylephrine), providing a combined α- and β-adrenergic agonist (norepinephrine) for BP support, and/or providing intra-aortic balloon.

Symptomatic HTN may occur when used w/ alpha-blockers. Reduced clearance w/ CYP3A4 inhibitors (e.g. cimetidine, delavirdine, erythromycin, itraconazole, ketoconazole). Increased plasma concentrations w/ HIV-protease inhibitors particularly by ritonavir-boosted regimens. Decreased plasma concentrations w/ CYP3A4 inducers (e.g. rifampicin, bosentan).
Potentially Fatal: Potentiation of hypotensive effects of nitrates of any form and nicorandil.

May increase plasma levels w/ grapefruit juice.

Description:
Mechanism of Action: Sildenafil inhibits phosphodiesterase type-5 (PDE-5) which is responsible for cyclic guanosine monophosphate (cGMP) degradation in the corpus cavernosum. Inhibition of PDE-5 increases cGMP which results in pulmonary vascular smooth muscle cells relaxation.
Onset: Approx 60 min.
Duration: 2-4 hr.
Pharmacokinetics:
Absorption: Rapidly absorbed from the GI tract. Bioavailability: Approx 40%. Time to peak plasma concentration: W/in 30-120 min.
Distribution: Widely distributed into body tissues. Plasma protein binding: Approx 96%.
Metabolism: Hepatically by CYP3A4 (major route) and CYP2C9 isoenzymes.
Excretion: Mainly via faeces (as metabolites); urine (lesser extent). Terminal half-life: Approx 4 hr.

Source: National Center for Biotechnology Information. PubChem Database. Sildenafil, CID=135398744, https://pubchem.ncbi.nlm.nih.gov/compound/Sildenafil (accessed on Jan. 23, 2020)

Store between 15-30°C.

Thuốc trị rối loạn cương và rối loạn xuất tinh / Các loại thuốc tim mạch khác

G04BE03 - sildenafil ; Belongs to the class of drugs used in erectile dysfunction.

Anon. Sildenafil. Lexicomp Online. Hudson, Ohio. Wolters Kluwer Clinical Drug Information, Inc. https://online.lexi.com. Accessed 07/11/2014.

Buckingham R (ed). Sildenafil Citrate. Martindale: The Complete Drug Reference [online]. London. Pharmaceutical Press. https://www.medicinescomplete.com. Accessed 07/11/2014.

McEvoy GK, Snow EK, Miller J et al (eds). Sildenafil Citrate. AHFS Drug Information (AHFS DI) [online]. American Society of Health-System Pharmacists (ASHP). https://www.medicinescomplete.com. Accessed 07/11/2014.

Revatio Tablet, Film Coated; Injection, Solution; Powder, for Suspension (Pfizer Laboratories Div Pfizer Inc). DailyMed. Source: U.S. National Library of Medicine. https://dailymed.nlm.nih.gov/dailymed/. Accessed 10/01/2014.