Formulary
Sildenafil: Indications, Dosing, Side Effects and Interactions
Sildenafil clinical drug profile including indications, dosing, side effects, cautions and interactions.
MedNext Academy | 5 min read
Sildenafil: Indications, Dosing, Side Effects and Interactions
Sildenafil clinical drug profile including indications, dosing, side effects, cautions and interactions.
Indications and dose
**Pulmonary arterial hypertension (initiated under specialist supervision)**
- **Adult** (By Mouth): 20 mg 3 times a day.
- **Adult** (By Intravenous Injection): 10 mg 3 times a day, use intravenous route when the oral route is not appropriate.
**Erectile dysfunction**
- **Adult** (By Mouth): Initially 50 mg, to be taken approximately 1 hour before sexual activity, adjusted according to response to 25-100 mg (max. per dose 100 mg) as required, to be taken as a single dose; maximum 1 dose per day.
**Digital ulcers [associated with systemic sclerosis]**
- **Adult** (By Mouth): 25 mg 3 times a day, increased to 50 mg 3 times a day.
**Pulmonary arterial hypertension (initiated under specialist supervision) for sildenafil**
- **Neonate** (By mouth): Initially 250-500 micrograms/kg every 4-8 hours, adjusted according to response, start with the lower dose and frequency, especially if used with other vasodilators; maximum 30 mg per day.
- **Child 1-11 months** (By mouth): Initially 250-500 micrograms/kg every 4-8 hours, adjusted according to response, start with the lower dose and frequency, especially if used with other vasodilators; maximum 30 mg per day.
- **Child 1-17 years (body-weight up to 20 kg)** (By mouth): 10 mg 3 times a day.
- **Child 1-17 years (body-weight 20 kg and above)** (By mouth): 20 mg 3 times a day.
Cautions
General cautions: Active peptic ulceration; anatomical deformation of the penis (e.g. angulation, cavernosal fibrosis, Peyronie's disease); autonomic dysfunction; bleeding disorders; cardiovascular disease; left ventricular outflow obstruction; predisposition to priapism (e.g. in sickle-cell disease, multiple myeloma, or leukaemia) Specific cautions: When used for Pulmonary arterial hypertension Hypotension (avoid if systolic blood pressure below 90 mmHg); intravascular volume depletion; pulmonary veno-occlusive disease Cautions, further information Elderly For phosphodiesterase type-5 inhibitors, Screening Tool of Older Persons' potentially inappropriate Prescriptions (STOPP) criteria to aid medication reviews (see Prescribing in the elderly for information): potentially inappropriate in severe heart failure characterised by hypotension i.e. systolic blood pressure less than 90 mmHg, or concurrent nitrate therapy for angina (risk of cardiovascular collapse).
Contraindications
General contra-indications: Hereditary degenerative retinal disorders; history of non-arteritic anterior ischaemic optic neuropathy; recent history of myocardial infarction; recent history of stroke Specific contra-indications: When used for Erectile dysfunction Avoid if systolic blood pressure below 90 mmHg (no information available); patients in whom vasodilation or sexual activity are inadvisable; recent unstable angina When used for Pulmonary arterial hypertension Sickle-cell anaemia
Side effects
Common or very common Alopecia; anaemia; anxiety; cough; diarrhoea; dizziness; fluid retention; gastrointestinal discomfort; gastrointestinal disorders; headaches; increased risk of infection; insomnia; nasal complaints; nausea; night sweats; pain; skin reactions; tremor; vasodilation; vision disorders Uncommon Arrhythmias; chest pain; drowsiness; dry eye; dry mouth; eye discomfort; eye disorders; eye inflammation; fatigue; feeling hot; gynaecomastia; haemorrhage; hypertension; hypotension; myalgia; numbness; palpitations; sinus congestion; tinnitus; vertigo; vomiting Rare or very rare Acute coronary syndrome; arteriosclerotic retinopathy; cerebrovascular insufficiency; glaucoma; haematospermia; hearing impairment; irritability; optic neuropathy (discontinue if sudden visual impairment occurs); oral hypoaesthesia; priapism; retinal occlusion; scleral discolouration; seizure; severe cutaneous adverse reactions (SCARs); sudden cardiac death; syncope; throat tightness
Interactions
**Severe interactions:**
- Due to the nitrate component it has the potential to result in aserious interaction with sildenafil.
- No significant interactions were shown when sildenafil (50mg) was co-administered with tolbutamide (250mg) or warfarin (40mg), both of which are metabolised by CYP2C9.
- Addition of a single dose of sildenafil to sacubitril/valsartan at steady state in patients with hypertension was associated with a significantly greater blood pressure reduction compared to...
**Other interactions (37):**
- Effects of other medicinal products on sildenafil In vitro studies: Sildenafil metabolism is principally mediated by the cytochrome P450 (CYP) isoforms 3A4 (major route) and 2C9 (minor route).
- Therefore, inhibitors of these isoenzymes may reduce sildenafil clearance and inducers of these isoenzymes may increase sildenafil clearance.
- In vivo studies: Population pharmacokinetic analysis of clinical trial data indicated a reduction in sildenafil clearance when co-administered with CYP3A4 inhibitors (such as ketoconazole,...
- Although no increased incidence of adverse events was observed in these patients, when sildenafil is administered concomitantly with CYP3A4 inhibitors, a starting dose of 25mg should be considered.
- Co-administration of the HIV protease inhibitor ritonavir, which is a highly potent P450 inhibitor, at steady state (500mg twice daily) with sildenafil (100mg single dose) resulted in a 300%...
- At 24 hours, the plasma levels of sildenafil were still approximately 200ng/ml, compared to approximately 5ng/ml when sildenafil was administered alone.
Pregnancy
Use only if potential benefit outweighs risk-no evidence of harm in animal studies.
Breast feeding
Manufacturer advises avoid-no information available.
Hepatic impairment
Manufacturer advises caution in mild to moderate impairment; avoid in severe impairment (no information available). Dose adjustments With intravenous use for Pulmonary arterial hypertension: Manufacturer advises if usual dose not tolerated, consider dose reduction to 10 mg twice daily in mild to moderate impairment. With oral use for Pulmonary arterial hypertension: Manufacturer advises if usual dose not tolerated, consider dose reduction to 20 mg twice daily in mild to moderate impairment. When used for Erectile dysfunction: Manufacturer advises consider initial dose reduction to 25 mg in mild to moderate impairment; adjust according to response.
Renal impairment
Dose adjustments When used for Erectile dysfunction: Consider initial dose of 25 mg if creatinine clearance less than 30 mL/minute. M See Prescribing in renal impairment . With oral use for Pulmonary arterial hypertension: If usual dose not tolerated, consider dose reduction to 20 mg twice daily. M With intravenous use for Pulmonary arterial hypertension: If usual dose not tolerated, consider dose reduction to 10 mg twice daily. M
Medicinal forms
Solution,Tablet,Suspension,Solution
Clinical governance
**Author:** MedNext Clinical Team. **Clinical reviewer:** Dr Shameer Deen, MBBS, MS, MRCS. **Sources:** BNF, Indian Pharmacopoeia, CIMS India. **Correction:** Report errors at support@mednext.academy.
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