Head-to-head clinical analysis & difference comparison: details on mechanism of action, dosing, half-life, interactions, and maternal-fetal safety.
CIALIS vs FINASTERIDE AND TADALAFIL
Clinician-reviewed, head-to-head comparison of mechanism, dosing, pharmacokinetics, and safety profiles.
Last clinically reviewed: July 2026 · OpiCalc Medical Review Team
Phosphodiesterase-5 (PDE5) inhibitor; increases c GMP levels, causing smooth muscle relaxation and vasodilation in the corpus cavernosum, enhancing erectile function.
Finasteride is a 5α-reductase inhibitor that inhibits conversion of testosterone to dihydrotestosterone (DHT). Tadalafil is a phosphodiesterase-5 (PDE5) inhibitor that enhances nitric oxide-mediated vasodilation by increasing cyclic guanosine monophosphate (c GMP) in smooth muscle.
Treatment of erectile dysfunction,Treatment of benign prostatic hyperplasia,Treatment of pulmonary arterial hypertension (as Adcirca)
Treatment of benign prostatic hyperplasia (BPH)
Tadalafil 10 mg or 20 mg orally as needed at least 30 minutes before sexual activity; maximum dosing frequency once daily. Alternative: 2.5 mg or 5 mg once daily for daily use.
One capsule containing finasteride 5 mg and tadalafil 5 mg orally once daily.
The terminal elimination half-life of tadalafil is approximately 17.5 hours in healthy subjects, which supports once-daily dosing for erectile dysfunction and once-daily use for benign prostatic hyperplasia. This long half-life distinguishes it from other PDE5 inhibitors.
Finasteride: 6-8 hours (elderly ~8 hours); Tadalafil: 17.5 hours (enables once-daily dosing).
Primarily hepatic via CYP3A4; minor pathways include CYP2C9 and glucuronidation.
Finasteride is extensively metabolized in the liver via CYP3A4; tadalafil is primarily metabolized by CYP3A4.
Following oral administration, tadalafil is predominantly eliminated by hepatic metabolism. The metabolites are excreted mainly in feces (approximately 61% of the dose) and to a lesser extent in urine (approximately 36% of the dose). No unchanged parent drug is detected in urine.
Finasteride: 57% feces, 39% urine (metabolites); Tadalafil: 36% urine, 61% feces (mostly metabolites).
Tadalafil is 94% bound to plasma proteins, primarily to albumin. The protein binding is independent of drug concentration over a wide range.
Finasteride: 90% bound to albumin and alpha-1-acid glycoprotein; Tadalafil: 94% bound to albumin.
The apparent volume of distribution (Vd/F) is approximately 63 L (or roughly 0.9 L/kg for a 70 kg individual), indicating distribution into tissues beyond the vascular space, including the penis and other target organs.
Finasteride: 76 L/kg (1.1 L/kg in elderly); Tadalafil: 63-77 L/kg (extensive tissue distribution).
Absolute oral bioavailability of tadalafil has not been formally determined; however, the drug is well absorbed after oral administration, with peak plasma concentrations reached in 0.5 to 6 hours (median 2 hours). Food does not affect the extent of absorption (AUC), though it may delay the rate (Tmax) by about 1–2 hours.
Finasteride: 63% oral (80% relative to IV); Tadalafil: 80% oral (bioavailability unaffected by food).
Cr Cl 30-50 m L/min: 5 mg once daily (max) for daily use; as-needed dosing: 10 mg not to exceed once every 48 hours. Cr Cl <30 m L/min: not recommended. Hemodialysis: not studied.
No adjustment for mild-moderate renal impairment (Cr Cl ≥30 m L/min). Avoid in severe renal impairment (Cr Cl <30 m L/min) or on dialysis due to increased tadalafil exposure.
Child-Pugh A and B: no dose adjustment necessary for as-needed dosing; daily use: caution, start at 5 mg once daily. Child-Pugh C: not recommended.
Child-Pugh A: no adjustment. Child-Pugh B: limit tadalafil dose to 5 mg (same as given); use caution. Child-Pugh C: avoid use.
Not indicated for pediatric patients under 18 years.
Not indicated in pediatric patients; safety and efficacy not established.
No dose adjustment required solely based on age; consider renal function and concomitant medications.
No dose adjustment required; monitor for orthostatic hypotension and dizziness, as elderly may be more sensitive to vasodilatory effects.
None
There is no FDA black box warning for the combination product. Individual components have warnings: Finasteride exposure during pregnancy may cause abnormalities of male external genitalia; Tadalafil is contraindicated in patients taking guanylate cyclase stimulators (e.g., riociguat) and nitrates.
Risk of hypotension with vasodilators or alpha-blockers,Contraindicated with nitrates due to severe hypotension risk,Patients with left ventricular outflow obstruction (e.g., aortic stenosis) should avoid use,Caution in patients with hypotension, severe hepatic impairment, or end-stage renal disease,Risk of priapism: advise immediate medical attention for erections lasting >4 hours,Decreased visual or hearing ability requiring discontinuation
Risk of priapism (tadalafil); sudden hearing loss (tadalafil); orthostatic hypotension with concomitant antihypertensives; prostate-specific antigen (PSA) level reduction (finasteride); risk of high-grade prostate cancer (finasteride); use in women of childbearing potential (finasteride teratogenicity).
Concomitant use of nitrates (any form) or riociguat,Hypersensitivity to tadalafil,Concomitant use with alpha-blockers (except for BPH with appropriate dosing)
Hypersensitivity to finasteride or tadalafil; concurrent use of nitrates or guanylate cyclase stimulators (e.g., riociguat); women who are or may become pregnant (finasteride teratogenicity).
Avoid high-fat meals prior to dosing as they may delay absorption and reduce peak plasma concentration. Avoid large quantities of grapefruit juice (more than 1 liter per day) as it may increase tadalafil exposure via CYP3A4 inhibition.
Avoid grapefruit and grapefruit juice as they increase tadalafil plasma concentrations. Alcohol may potentiate hypotension and dizziness. High-fat meals may delay tadalafil absorption but do not reduce efficacy.
FDA Pregnancy Category B. Animal studies show no evidence of teratogenicity or embryotoxicity. No adequate, well-controlled studies in pregnant women. Risk cannot be ruled out; use only if clearly needed.
Finasteride: Contraindicated in pregnancy due to risk of hypospadias in male fetuses (Category X). Tadalafil: Category B; no fetal harm in animal studies, but insufficient human data. Avoid combination in pregnant women.
Excretion in human milk unknown. Not recommended for use in nursing mothers. M/P ratio not determined.
Finasteride: Excreted in breast milk (M/P ratio unknown); not recommended. Tadalafil: Presence in breast milk unknown; avoid due to potential adverse effects.
No specific dose adjustments studied in pregnancy. Use lowest effective dose if necessary, with caution for increased plasma volume and renal clearance potentially altering pharmacokinetics.
Contraindicated in pregnancy; pharmacokinetic changes in pregnancy do not apply as use is not recommended. No dose adjustment applicable.
Tadalafil (Cialis) has a 17.5-hour half-life allowing once-daily dosing for ED or daily for BPH/LUTS. Avoid use with nitrates; may cause prolonged erection. Onset of action is 30-60 minutes, and effect may last up to 36 hours. Use with caution in patients with left ventricular outflow obstruction or severe hepatic impairment.
Finasteride and tadalafil combination is used for benign prostatic hyperplasia (BPH). Tadalafil may cause priapism; advise immediate medical attention for erections lasting >4 hours. Finasteride decreases serum PSA by ~50%; double PSA values for interpretation. Avoid coadministration with strong CYP3A4 inhibitors (e.g., ketoconazole) due to increased tadalafil exposure. Tadalafil is contraindicated with nitrates due to severe hypotension. Assess cardiovascular stability before prescribing tadalafil.
Do not take tadalafil if you take any form of nitrate medication (e.g., nitroglycerin) for chest pain.,Seek immediate medical help if you have an erection lasting more than 4 hours.,Avoid alcohol consumption as it may increase the risk of dizziness and low blood pressure.,Take tadalafil at least 30 minutes before sexual activity; effect can last up to 36 hours.,For daily use, take at the same time each day without regard to timing of sexual activity.,Grapefruit and grapefruit juice may increase tadalafil levels; avoid large amounts.,Inform your doctor of all medications you take, especially alpha-blockers, antihypertensives, and antifungal or antibiotic drugs.
Take the medication at the same time daily with or without food.,Seek emergency care for erections lasting longer than 4 hours.,Inform your doctor about all medications, especially nitrates or alpha-blockers.,Finasteride may reduce PSA levels; do not stop taking before PSA testing without consulting your doctor.,Avoid grapefruit juice as it may increase side effects.,Tadalafil may cause dizziness or syncope; avoid driving if affected.
No interactions on record
"Tadalafil, a phosphodiesterase-5 (PDE5) inhibitor, potentiates the hypotensive effect of trandolapril, an angiotensin-converting enzyme (ACE) inhibitor, by enhancing cyclic guanosine monophosphate (cGMP)-mediated vasodilation. This additive hemodynamic effect can lead to symptomatic hypotension, particularly in patients with volume depletion, pre-existing low blood pressure, or those on multiple antihypertensives. Clinically, this interaction manifests as a risk of excessive blood pressure reduction, especially when tadalafil is taken within 4-6 hours of trandolapril administration."
"Posaconazole, an azole antifungal, is a potent inhibitor of CYP3A4, while tadalafil is a CYP3A4 substrate. Coadministration significantly increases tadalafil exposure, leading to elevated risk of adverse effects such as hypotension, syncope, and priapism. The interaction is well-documented and requires dose adjustment or avoidance."
"Tadalafil, a phosphodiesterase-5 (PDE5) inhibitor, potentiates the vasoconstrictive and hypertensive effects of xylometazoline, an alpha-1 adrenergic receptor agonist. This occurs through tadalafil's inhibition of cGMP degradation in vascular smooth muscle, which counteracts the normal nitric oxide-mediated vasodilation and enhances the pressor response to alpha-agonists. Clinically, this interaction can lead to excessive and prolonged increases in blood pressure, potentially resulting in hypertensive crisis, especially in patients with underlying cardiovascular conditions."
Explore head-to-head clinical comparisons of other medications in the same therapeutic classes.
Common clinical questions about CIALIS vs FINASTERIDE AND TADALAFIL, answered by our medical review team.
CIALIS is a PDE5 Inhibitor that works by Phosphodiesterase-5 (PDE5) inhibitor; increases c GMP levels, causing smooth muscle relaxation and vasodilation in the corpus cavernosum, enhancing erectile function.. FINASTERIDE AND TADALAFIL is a PDE5 Inhibitor that works by Finasteride is a 5α-reductase inhibitor that inhibits conversion of testosterone to dihydrotestosterone (DHT). Tadalafil is a phosphodiesterase-5 (PDE5) inhibitor that enhances nitric oxide-mediated vasodilation by increasing cyclic guanosine monophosphate (c GMP) in smooth muscle.. They differ in pharmacokinetic profiles, FDA-approved indications, and side effect profiles.
Potency comparisons between CIALIS and FINASTERIDE AND TADALAFIL depend on the specific clinical indication. These are both PDE5 Inhibitor agents and are not directly interchangeable by dose. A physician or clinical pharmacist should guide any therapeutic switching decisions.
The standard adult dose of CIALIS is: Tadalafil 10 mg or 20 mg orally as needed at least 30 minutes before sexual activity; maximum dosing frequency once daily. Alternative: 2.5 mg or 5 mg once daily for daily use.. The standard adult dose of FINASTERIDE AND TADALAFIL is: One capsule containing finasteride 5 mg and tadalafil 5 mg orally once daily.. Dosing should always be individualized based on indication, renal and hepatic function, age, and other patient factors.
No direct drug-drug interaction has been formally documented between CIALIS and FINASTERIDE AND TADALAFIL in current clinical databases. However, individual patient risk factors including other medications, organ function, and comorbidities should always be evaluated by a qualified healthcare provider.
The maternal-fetal safety profiles differ. CIALIS is classified as Category C. FDA Pregnancy Category B. Animal studies show no evidence of teratogenicity or embryotoxicity. No adequate, well-controlled studies in pregnant women. Risk cannot be ruled out; use. FINASTERIDE AND TADALAFIL is classified as Category A/B. Finasteride: Contraindicated in pregnancy due to risk of hypospadias in male fetuses (Category X). Tadalafil: Category B; no fetal harm in animal studies, but insufficient human da. Always consult a maternal-fetal medicine specialist before taking either drug during pregnancy or lactation.