Cialis (tadalafil): uses, dosage, side effects and refills

Tadalafil is the long-acting member of the PDE5 inhibitor family that also includes sildenafil. Eli Lilly's Cialis was approved for erectile dysfunction on 21 November 2003 (Drugs@FDA, NDA 021368) and later gained approvals for BPH and for men with both conditions. Generic tadalafil is now widely available. ClinCalc's DrugStats recorded about 5.5 million prescriptions in 2024, ranking it 119th.

Its defining feature is duration. The half-life is 17.5 hours in healthy men, and the Cialis label says erectile function improved over placebo for up to 36 hours after a dose (Cialis label, 2.1 and 12.3). That long window is why it can be taken as a small daily dose rather than only before sex.

The same molecule is sold at 20 mg tablets under other names, Adcirca and Alyq, and as Tadliq suspension, for pulmonary arterial hypertension (PAH). Those products are dosed differently and managed by specialists. This page covers tadalafil for ED and BPH; the PAH uses are described only briefly.

FDA-approved uses of Cialis (Cialis label, section 1)

• Erectile dysfunction (ED).
• Signs and symptoms of BPH: frequency, urgency, waking at night, weak stream, straining and incomplete emptying.
• ED and BPH together.
• When tadalafil is started with finasteride for BPH, the label recommends the combination for up to 26 weeks, because tadalafil's added benefit fades over that period.

What the trials showed

• ED: in two US trials, tadalafil 20 mg raised the erectile function score by 6.9 and 9.3 points versus almost no change on placebo. The share of attempts with successful intercourse rose by 34 and 44 percentage points, compared with 5 and 4 on placebo (label, Table 11).
• BPH: 5 mg daily lowered the IPSS by 4.8 and 5.6 points in Studies J and K, versus 2.2 and 3.6 on placebo, from baselines near 17 (label, Table 19). Urine flow did not differ significantly from placebo. These are averages.

Other approved uses of tadalafil (different brands)

• PAH, to improve exercise ability, as Adcirca, Alyq or Tadliq (MedlinePlus). This is specialist care.

Off-label

MedlinePlus notes other uses may be prescribed. Use in women, or for conditions not listed above, is off-label.

Tadalafil does not increase sexual desire and does not protect against pregnancy or sexually transmitted infections (MedlinePlus; label, 5.13).

An erection depends on nitric oxide released during sexual stimulation. Nitric oxide raises cyclic GMP (cGMP) in the smooth muscle of the penis, which relaxes the muscle and lets blood fill the erectile tissue. The enzyme PDE5 breaks cGMP down. Tadalafil blocks PDE5, so cGMP lasts longer and the response to stimulation is stronger (Cialis label, 12.1). Without sexual stimulation, nothing happens.

PDE5 is also present in the prostate, bladder and their blood vessels. Relaxing smooth muscle there is thought to explain the BPH benefit, and in the lung's blood vessels it explains the PAH use.

Pharmacokinetics (label, 12.3)

• Peak levels arrive between 30 minutes and 6 hours after a dose, with a median of 2 hours.
• Food does not change absorption.
• The liver clears it through CYP3A4, which is why ketoconazole more than quadrupled exposure (AUC up 312%) and rifampin cut it by 88%.
• The half-life of 17.5 hours means daily dosing builds a steady level.

Why nitrates are dangerous. Nitrates work by delivering nitric oxide. With PDE5 blocked, the effect multiplies. In a label study, tadalafil 20 mg amplified the blood pressure drop from sublingual nitroglycerin at every time point up to 24 hours; by 48 hours, the interaction had largely disappeared (12.2).

Do not take tadalafil if you (Cialis label, section 4):

• use any nitrate, regularly or now and then: nitroglycerin tablets, spray, patch or ointment; isosorbide mononitrate or dinitrate; or recreational "poppers" (amyl or butyl nitrite);
• take riociguat (Adempas) or another guanylate cyclase stimulator;
• had a serious allergic reaction to tadalafil (Cialis or Adcirca), including Stevens-Johnson syndrome.

Tell your prescriber about:

• Heart health. The label says tadalafil is not recommended after a heart attack in the past 90 days, with unstable angina or angina during sex, heart failure (NYHA class 2 or worse) in the past 6 months, uncontrolled arrhythmia, blood pressure under 90/50 or uncontrolled hypertension, or a stroke in the past 6 months (5.1). Aortic stenosis also needs care.
• Alpha blockers such as tamsulosin or doxazosin, and other blood pressure medicines (5.6).
• Past sudden vision loss (NAION) or a "crowded" optic disc; retinitis pigmentosa (5.4).
• Conditions that raise priapism risk: sickle cell anemia, multiple myeloma, leukemia, Peyronie's disease (5.3).
• Kidney or liver disease, which changes the dose.
• Ketoconazole, itraconazole, ritonavir or other HIV protease inhibitors.
• Bleeding disorders or active stomach ulcers (5.12).

Ask: "Is my heart healthy enough for sexual activity, and what should I do if I get chest pain after taking tadalafil?"

As needed for ED (Cialis label, 2.1)

• The usual starting dose is 10 mg before sexual activity. Your prescriber may raise it to 20 mg or lower it to 5 mg.
• No more than once a day.
• MedlinePlus says it is usually taken at least 30 minutes before sex. The label notes benefit lasts up to 36 hours, so exact timing is flexible.
• Sexual stimulation is still needed.

Once daily for ED (2.2)

• Start at 2.5 mg every day at about the same time, regardless of when you have sex; it may be raised to 5 mg.

Once daily for BPH or ED with BPH (2.3, 2.4)

• 5 mg every day at about the same time.
• If you take an alpha blocker for BPH, the label says to stop it at least one day before starting tadalafil for BPH, and the combination is not recommended for BPH. Do this only on your prescriber's instruction.

For every schedule

• With or without food (2.5).
• Do not split tablets; take the entire dose (section 2).
• Limit alcohol: 5 or more drinks with tadalafil raises the risk of dizziness and low standing blood pressure (5.9).
• If you get chest pain after taking tadalafil, call 911 and tell responders when you took it. Do not take nitroglycerin unless a clinician decides it is needed under monitoring.

Your prescriber chooses the schedule and dose. The table summarizes the Cialis label for reference.

• Liver: as-needed doses should not exceed 10 mg in mild or moderate impairment; tadalafil is not recommended in severe impairment (2.6).
• Kidneys: limits tighten with creatinine clearance below 50 mL/min, as in the table. Temi's creatinine clearance calculator explains the measure.
• Older adults: exposure was 25% higher in men 65 and over, but the label sets no age-based change.
• Alpha blockers: for ED, men should be stable on the alpha blocker first and start tadalafil at the lowest dose.
• No doubling up: do not combine tadalafil with sildenafil, vardenafil, avanafil or a PAH tadalafil product (5.11).

As-needed dosing has no missed dose; you simply take it before sex, never more than once a day. On a daily schedule for ED or BPH, MedlinePlus says to take the forgotten tablet once you notice, unless the next is nearly due, in which case let it go. Never take a double dose or more than one dose in a day.

Healthy volunteers took single doses up to 500 mg, and patients took 100 mg a day, with side effects similar to normal doses (Cialis label, 10). Expect headache, flushing, indigestion, muscle aches and dizziness. Dialysis removes very little. Call 1-800-222-1222 (Poison Help) about an accidental overdose; call 911 for fainting, chest pain, a severe blood pressure drop or an erection lasting more than 4 hours.

• All nitrates, including nitroglycerin and isosorbide products, and "poppers" (alkyl nitrites).
• Riociguat.
• Heavy drinking: 5 or more units at once with tadalafil.
• Grapefruit juice in large amounts: the label says it would likely increase tadalafil exposure.
• Other ED pills, including sildenafil, vardenafil, avanafil or a PAH tadalafil product (Cialis label, 5.11).
• Ignoring warning signs: sudden vision loss, sudden hearing loss, or an erection lasting over 4 hours.

The Cialis label states tadalafil is not indicated for use in females. Animal studies showed no birth defects at exposures up to 11 times the maximum human dose, though high doses reduced pup survival in rats (Cialis label, 8.1). Tadalafil reaches rat milk at about 2.4 times plasma levels; human data are lacking (8.2). PAH treatment in pregnancy is specialist care.

Male fertility: two studies found lower sperm concentrations after 6 to 9 months of daily 10 or 20 mg, while a third did not; hormone levels were unchanged, and the clinical significance is unknown (8.3).

Tadalafil tablets are labeled for storage at 25°C (77°F), with short excursions between 15°C and 30°C permitted (Cialis label, 16). Keep the original container closed, out of the bathroom, and away from children. Bring unused tablets to a pharmacy disposal kiosk.

Related medicines, each with its own page:

• Sildenafil: a shorter-acting PDE5 inhibitor for ED, also used in PAH.
• Tamsulosin: an alpha blocker for BPH that needs care when combined with tadalafil.
• Finasteride: shrinks the prostate; approved with tadalafil for up to 26 weeks.
• Nitroglycerin: a nitrate that must never be combined with tadalafil.
• Isosorbide mononitrate: a daily nitrate, also contraindicated.
• Testosterone: treats low testosterone, a separate cause of sexual symptoms.

Tadalafil for ED or BPH is non-controlled, and Temi physicians can prescribe it after an online review. Men renewing a dose they already use pay $15 per refill review, and Temi Care members (membership) pay nothing (usetemi.com/prescription/refills, checked 5 Oct 2026). Someone new to tadalafil pays $79 for the first-time review (usetemi.com/get-prescribed, checked 5 Oct 2026), which screens for nitrate use, heart disease and blood pressure drugs. The PAH brands are specialist territory: whether a Temi physician can help there is decided individually and is never guaranteed. Reviews finish within 48 hours, and prescriptions go to your chosen pharmacy.