sildenafil

CLINICAL USE

Treatment of erectile dysfunction (ED) To increase exercise ability in pulmonary arterial hypertension

DOSE IN NORMAL RENAL FUNCTION

ED: 25–100 mg 0.5–4 hours before sexual intercourse (ideally, about 1 hour); no more than 1 dose per dayPulmonary arterial hypertension: 20 mg 3 times daily

PHARMACOKINETICS

Molecular weight :666.7 (as citrate)

%Protein binding :96

%Excreted unchanged in urine : <2

Volume of distribution (L/kg) :1–2

half-life – normal/ESRD (hrs) :4/Increased

DOSE IN RENAL IMPAIRMENT

GFR (mL/MIN)

30–50 Dose as in normal renal function10–30 Dose as in normal renal function ED: Initial dose 25 mg and increase if required

<10 : Dose as in normal renal function ED: Initial dose 25 mg and increase if required

DOSE IN PATIENTS UNDERGOING RENAL REPLACEMENT THERAPIES

CAPD :Unlikely to be dialysed. Dose as in GFR <10 mL/min

HD :Unlikely to be dialysed. Dose as in GFR <10 mL/min

HDF/high flux :Not dialysed. Dose as in GFR <10 mL/min

CAV/VVHD :Unlikely to be dialysed. Dose as in GFR 10 to 20 mL/min

IMPORTANT DRUG INTERACTIONS

Potentially hazardous interactions with other drugsAlpha-blockers: enhanced hypotensive effect – avoid for 4 hours after sildenafil

Antivirals: ritonavir significantly increases sildenafil concentration – avoid concomitant use; concentration possibly increased by saquinavir, amprenavir, indinavir and nelfinavir – reduce dose of sildenafil; side effects possibly increased by atazanavirNicorandil: enhanced hypotensive effect – avoid concomitant use

Nitrates: enhanced hypotensive effect – absolutely contraindicated

ADMINISTRATION

Reconstition

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Route

Oral

Rate of Administration

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Comments

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OTHER INFORMATION

Dialysis is not expected to increase clearance as sildenafil is highly protein boundPatients should seek prompt medical advice if their erections last for more than 4 hoursRecommend use on non-dialysis days due to hypotension. In peritoneal dialysis, treatment with sildenafil is well toleratedAnecdotally it has been used at Guy’s hospital, London for diabetic gastroparesis at a dose of 25 mg 3 times a dayThe use of sildenafil is potentially hazardous in patients with active coronary ischaemia, those with congestive heart failure, and those with complicated multi-drug antihypertensive therapy regimensIn 9 patients on maintenance haemodialysis, sildenafil 50 mg appeared to produce firmer erections and greater sexual satisfaction, but the effects were prolonged for up to 48 hours after administration.

See how to identify renal failure stages according to GFR calculation

See how to diagnose irreversible renal disease

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