Tadalafil
Medication
PDE5 inhibitor
other
Not medical advice. Check with your doctor or pharmacist before you start, stop or change the timing of anything you take.
How to use
What it’s for
HealthHub: erectile dysfunction, enlarged prostate, pah
When to take
HealthHub: as-needed dosing works from 30 min to 36 hours
Take with
HealthHub: with or without food · grapefruit interacts
Pros & cons
Pros
- HealthHub: effective for up to 36 hours
- SG label: 5 mg daily covers ed and enlarged prostate
- HealthHub: taken with or without food
Cons
- HealthHub: flushing, headache, nasal congestion
- SG label: any organic nitrate is a contraindication
- HealthHub: rare priapism, sudden vision or hearing loss
Sources
- HSA — Listing of Registered Therapeutic Products (data.gov.sg open dataset, 5,511 rows, cached in full and filtered locally) · read 2026-08-27
what it says
“All 32 registered tadalafil products read Forensicclassification 'Prescription Only' — SIN12181P CIALIS TABLET 20 mg · SIN13632P CIALIS TABLET 5 mg · SIN16839P SYNERRV · SIN16131P TADAFIL 20 · SIN16072P TADACCORD 20 · SIN16580P TADILAS”
- HealthHub (National Medication Information workgroup, SG) — Tadalafil: what is this medication for · read 2026-08-27
what it says
“Tadalafil is used to treat erectile dysfunction … It can also be used for urinary symptoms associated with benign prostatic hyperplasia (enlarged prostate) … Tadalafil is also used to treat high blood pressure in the blood vessels in the lungs”
- HealthHub — Tadalafil: how should I take this medication · read 2026-08-27
what it says
“When taking this medication on an as-needed basis, take before sexual activity. It starts to work within 30 minutes and is effective for up to 36 hours … This medication may be taken with or without food.”
- HealthHub — Tadalafil: common side effects · read 2026-08-27
what it says
“Facial flushing where the skin on your face feels hot; Giddiness due to lowering of blood pressure; Headache; Nausea; Back pain, muscle aches, pain in arms and legs; Nasal congestion”
- HealthHub — Tadalafil: rare but serious side effects · read 2026-08-27
what it says
“Priapism (an erection that will not go away) … Sudden vision loss in one or both eyes can be a sign of a serious eye problem called non-arteritic anterior ischemic optic neuropathy (NAION). Sudden hearing decrease or hearing loss”
- HealthHub — Tadalafil: precautions on nitrates and alpha-blockers · read 2026-08-27
what it says
“The combination of nitrates with tadalafil may lead to a dangerous fall in your blood pressure … You are taking medicines called Alpha-1 Blockers (such as Tamsulosin, Terazosin, Prazosin, Alfuzosin), as the combination may further lower your blood pressure.”
- HealthHub — Tadalafil: what precautions should I take · read 2026-08-27
what it says
“You recently had a stroke or a heart attack, low blood pressure or uncontrolled high blood pressure. You have severe heart, liver or kidney problem. You have certain rare inherited eye diseases (such as retinitis pigmentosa)”
- HealthHub — Tadalafil: what food or medication should I avoid · read 2026-08-27
what it says
“Avoid taking grapefruit, or grapefruit juice as they may interact with your medication and increase the risk of side-effects.”
- Singapore National Drug Formulary (HSA/MOH) — CIALIS TABLET 20 MG [SIN12181P], section 4.1 Therapeutic indications · read 2026-08-27
what it says
“Treatment of erectile dysfunction (ED) in adult males … Treatment of the signs and symptoms of benign prostatic hyperplasia (BPH) … Cialis is not indicated for use by women.”
- Singapore National Drug Formulary — CIALIS TABLET 20 MG [SIN12181P], section 4.2 Posology, Cialis for Use as Needed · read 2026-08-27
what it says
“The recommended dose is 10mg taken prior to anticipated sexual activity. In those patients in whom tadalafil 10mg does not produce an adequate effect, the maximum dose is 20mg and the maximum dosing frequency is once per day.”
- Singapore National Drug Formulary — CIALIS TABLET 20 MG [SIN12181P], BPH and ED/BPH dosing · read 2026-08-27
what it says
“Benign Prostatic Hyperplasia: The recommended dose is 5mg, taken at approximately the same time every day … Erectile Dysfunction and Benign Prostatic Hyperplasia: The recommended dose is 5mg”
- Singapore National Drug Formulary — CIALIS TABLET 20 MG [SIN12181P], men with renal impairment · read 2026-08-27
what it says
“Moderate (creatinine clearance 31 to 50 ml/min): … the maximum dose is 10mg not more than once in every 48 hours. Severe … The maximum dose is 5mg not more than once in every 72 hours”
- Singapore National Drug Formulary — CIALIS TABLET 20 MG [SIN12181P], patients taking CYP3A4 inhibitors · read 2026-08-27
what it says
“For patients taking concomitant potent inhibitors of CYP3A4, such as ketoconazole or ritonavir, the maximum recommended dose of Cialis is 10mg, not to exceed once every 72 hours”
- Singapore National Drug Formulary — CIALIS TABLET 20 MG [SIN12181P], section 4.3 Contraindications (nitrates, riociguat) · read 2026-08-27
what it says
“administration of Cialis to patients who are using any form of organic nitrate is contraindicated … The co-administration of PDE5 inhibitors, including tadalafil, with guanylate cyclase stimulators, such as riociguat, is contraindicated”
- Singapore National Drug Formulary — CIALIS TABLET 20 MG [SIN12181P], cardiac and ocular contraindications · read 2026-08-27
what it says
“Cialis must not be used in men with cardiac disease for whom sexual activity is inadvisable … Cialis is contraindicated in patients who have loss of vision in one eye because of non-arteritic anterior ischaemic optic neuropathy (NAION)”
Updated 2026-08-29. Every line above traces to a numbered source. Kozen-X is not a medical device and does not give medical advice. It lists what published sources have written down — nothing more. A pair not listed is unrecorded, not cleared. Before you start, stop or re-time anything, talk to your doctor or pharmacist.