medicationPrescription only (US)
TadalafilBenefits, Dosage & Interactions
Also known as: Cialis
Cialis is the brand name for tadalafil, a PDE5 inhibitor approved for erectile dysfunction, the urinary symptoms of benign prostatic hyperplasia, and pulmonary arterial hypertension (as Adcirca). It blocks the enzyme that breaks down cGMP, so nitric-oxide signaling relaxes smooth muscle and blood flow improves.
Researched by DoseRoutine R&D TeamReviewed for accuracy by Nicholas Alexander, RSELast updated
Evidence: Strong — 1 human randomized trial and regulatory approval on file.
Evidence strengthStrong · 4/4
PreclinicalStrong human evidence
1 human randomized trial and regulatory approval on file.
Quick answer
Cialis is the brand name for tadalafil, a PDE5 inhibitor approved for erectile dysfunction, the urinary symptoms of benign prostatic hyperplasia, and pulmonary arterial hypertension (as Adcirca). It blocks the enzyme that breaks down cGMP, so nitric-oxide signaling relaxes smooth muscle and blood flow improves. Its defining feature is duration — an effective window of roughly 36 hours, far longer than sildenafil.
- Generic name
- Tadalafil
- Drug class
- PDE5 inhibitor
- Approved for
- Erectile dysfunction, BPH symptoms, pulmonary hypertension
- Onset
- About 30–60 minutes
- Duration
- Up to ~36 hours — the source of the "weekend pill" nickname
- Absolute contraindication
- Any nitrate medication (dangerous blood-pressure drop)
Compiled by DoseRoutine from public sources including NIH/MedlinePlus, the FDA label, Mayo Clinic and PubChem. Educational information, not medical advice.
Plasma half-life
~17.5 h
Default unit
mg
What published protocols report
Ranges documented in the literature, shown for reference. DoseRoutine does not recommend an amount — your prescriber or the product label sets the dose.
Reported for Tadalafil in the cited sources. Published ranges are not dosing advice.
Tadalafil compared with similar compounds
| Attribute | Sildenafil | Tadalafil |
|---|---|---|
| Class | PDE5 inhibitor | PDE5 inhibitor |
| Route | Oral | Oral |
| Half-life | 3-5 hours | ~17.5 hours |
| Evidence grade | Strong | Strong |
| Oral stability | Orally active | Orally active |
| Typical published cycle | As needed | As needed or once daily |
| Main studied use | Erectile dysfunction | Erectile dysfunction and BPH symptoms |
References & evidence
Documents the Tadalafil entry is written from. Each number matches an inline marker above.
- [1]Role of application of tadalafil 5 mg once-daily (>=6 months) in men with erectile dysfunction from six randomized controlled trialsMa J, Liu Z, Wu J, et al. · Translational Andrology and Urology · 2020 · Peer-reviewed · PMID 32676425
- [2]Long-term tadalafil once daily in Chinese men with erectile dysfunction: a 2-year final analysis of a post-marketing, multicenter, randomized, open-label trialJiang H, Zhao LM, Yan S, et al. · Asian Journal of Andrology · 2024 · Peer-reviewed · PMID 38284776
How to track Tadalafil doses
Tracking Tadalafil well takes four fields and a habit. Here is what to record so the log is still useful in three months.
- 1
Add the dose and unit
Log Tadalafil with its dose in mg so totals stay comparable over time — including days when you split the dose or skip it.
- 2
Set the time of day and food rule
Pick the time you actually take it. Reminders fire at that time and can export to your calendar.
- 3
Check it against the rest of the stack
Run Tadalafil through the interaction checker against everything else in the routine — supplements, peptides, hormones and prescriptions — before it becomes a daily habit.
- 4
Log adherence, not intentions
Mark each dose taken, skipped or delayed as it happens. Weeks of honest logs are what make an adherence rate or a trend line meaningful; retrospective guessing is not.
- 5
Review against outcomes
With a reported half-life around 17.5 h, effects and timing shifts show up over days rather than instantly. Review Tadalafil alongside your logged metrics and any relevant blood work every few weeks before changing the dose.
What to log each time
- Dose in mg
- Time of day
- Taken / skipped / delayed
- Any side effects or notable changes
References & Evidence
Sources on this page that document Tadalafil dosing, timing and safety.
- [1]National Center for Biotechnology Information View source
Educational information only — not medical advice. Dose ranges vary by person, indication and prescriber.
What is Tadalafil studied for?
What is Tadalafil?Sources for this section: Jumps to this entry in the sources and references list at the end of the page.
Tadalafil is a medication primarily known for treating erectile dysfunction (ED), benign prostatic hyperplasia (BPH) symptoms, and pulmonary arterial hypertension (PAH). It belongs to a class of drugs called phosphodiesterase-5 (PDE5) inhibitors. Originally marketed under the brand name Cialis, it is available in various strengths and formulations. Tadalafil distinguishes itself from other PDE5 inhibitors by its longer half-life, allowing for effects lasting up to 36 hours, earning it the nickname "the weekend pill." Its use for ED involves assisting in achieving and maintaining an erection by increasing blood flow to the penis following sexual stimulation. For BPH, it helps relax muscles in the prostate and bladder, improving urinary symptoms. In PAH, it relaxes blood vessels in the lungs, reducing pressure and improving exercise capacity (FDA label, DrugBank).
What does the research say about Tadalafil?
Tap a section to expand.
Tadalafil acts as a selective inhibitor of cyclic guanosine monophosphate (cGMP)-specific phosphodiesterase type 5 (PDE5). In the context of erectile dysfunction, sexual stimulation leads to the local release of nitric oxide (NO) in the corpus cavernosum. NO activates guanylate cyclase, which increases levels of cGMP. cGMP causes smooth muscle relaxation in the corpus cavernosum, leading to increased blood flow into the penis and subsequent erection. PDE5 is responsible for the degradation of cGMP in the corpus cavernosum. By inhibiting PDE5, tadalafil increases cGMP levels, enhancing the relaxation of smooth muscle and promoting blood flow (FDA label, PubChem).
For benign prostatic hyperplasia, the exact mechanism is not fully understood but is thought to involve inhibition of PDE5 in prostate, bladder, and vascular smooth muscle, leading to relaxation of these tissues and improved urinary symptoms. In pulmonary arterial hypertension, tadalafil inhibits PDE5 in the pulmonary vasculature, resulting in vasodilation and a reduction in pulmonary arterial pressure (DrugBank, EMA SmPC).
Source for this section: Sources for How does Tadalafil work?: Jumps to this entry in the sources and references list at the end of the page.
- **Erectile Dysfunction (ED)**: Tadalafil improves the ability to achieve and maintain an erection sufficient for sexual activity. Clinical trials have consistently demonstrated its efficacy across various severities of ED, including men with underlying conditions such as diabetes or post-prostatectomy ED (Cochrane, FDA label).
- **Benign Prostatic Hyperplasia (BPH)**: It is approved for the treatment of signs and symptoms of BPH, including frequent urination, urgency, weak stream, and incomplete bladder emptying. Studies show significant improvements in the International Prostate Symptom Score (IPSS) in men treated with tadalafil (FDA label, Mayo Clinic).
- **Pulmonary Arterial Hypertension (PAH)**: Tadalafil is used to improve exercise capacity in patients with PAH. It helps relax the blood vessels in the lungs, which can reduce the workload on the heart and alleviate symptoms like shortness of breath (FDA label, NIH ODS).
- **Extended Duration of Action**: Unlike some other PDE5 inhibitors, tadalafil has a prolonged half-life, providing an effect that can last up to 36 hours. This allows for greater spontaneity compared to medications that require more precise timing relative to sexual activity (Examine.com, FDA label).
Numerous studies support the efficacy and safety of tadalafil across its approved indications. For erectile dysfunction, a meta-analysis of randomized controlled trials involving thousands of participants demonstrated that tadalafil significantly improved erectile function according to standardized questionnaires like the International Index of Erectile Function (IIEF) scores compared to placebo (Cochrane). Studies have shown positive response rates ranging from 60% to 80% depending on the population and dosage (Examine.com).
In the treatment of benign prostatic hyperplasia, clinical trials have shown that tadalafil significantly reduces the International Prostate Symptom Score (IPSS) and improves quality of life measures. For example, a large placebo-controlled study published in the Journal of Urology found significant improvements in both voiding and storage symptoms after 12 weeks of daily tadalafil administration (NIH ODS).
For pulmonary arterial hypertension, studies have demonstrated that tadalafil improves exercise capacity, as measured by the 6-minute walk distance, and reduces pulmonary vascular resistance. A key clinical trial showed that patients treated with tadalafil experienced significant improvements in exercise capacity and clinical worsening compared to placebo (MedlinePlus, FDA label).
Overall, the evidence base for tadalafil is robust, with consistent findings across various patient populations and indications, supporting its therapeutic benefits.
Common side effects include headache, indigestion (dyspepsia), back pain, muscle aches, flushing, and nasal congestion. These effects are generally mild to moderate and temporary. Back pain and muscle aches are more commonly reported with tadalafil than with some other PDE5 inhibitors, usually appearing 12 to 24 hours after dosing and resolving within two days. Less common but potentially serious side effects include sudden decrease or loss of vision (NAION), sudden decrease or loss of hearing, priapism (an erection lasting more than 4 hours), and allergic reactions. If any severe or persistent side effects occur, immediate medical attention is advised (FDA label, Mayo Clinic). This is educational information, not medical advice — consult a qualified clinician before starting, stopping or combining any compound.
Individuals with heart problems should use tadalafil with caution, as sexual activity itself poses a risk. Patients who have had a heart attack, stroke, or life-threatening irregular heartbeat in the last 6 months, or those with uncontrolled high blood pressure or unstable angina, typically should not use tadalafil. Avoid use if you have severe liver or kidney impairment without specific medical guidance. Patients with anatomical deformation of the penis (such as angulation, cavernosal fibrosis, or Peyronie's disease), or those with conditions that may predispose them to priapism (such as sickle cell anemia, multiple myeloma, or leukemia) should use tadalafil with caution and under medical supervision (FDA label, MedlinePlus). This is educational information, not medical advice — consult a qualified clinician before starting, stopping or combining any compound.
Tadalafil is contraindicated in patients taking any form of organic nitrates, either regularly or intermittently, due to the potential for severe hypotension (a dangerous drop in blood pressure). This includes nitroglycerin, isosorbide dinitrate, and isosorbide mononitrate. It is also contraindicated in patients with a known hypersensitivity to tadalafil or any of its components. Concurrent use with guanylate cyclase stimulators, such as riociguat, is also contraindicated due to the risk of severe hypotension. Men for whom sexual activity is inadvisable due to cardiovascular status are generally contraindicated from using tadalafil for ED (FDA label, DrugBank). This is educational information, not medical advice — consult a qualified clinician before starting, stopping or combining any compound.
- **Nitrates (e.g., nitroglycerin, isosorbide dinitrate/mononitrate)**: Concurrent use with tadalafil is absolutely contraindicated due to the risk of a severe and potentially fatal drop in blood pressure. This interaction can occur even if nitrates are taken hours apart from tadalafil, given tadalafil's long half-life (FDA label).
- **Alpha-Blockers (e.g., tamsulosin, doxazosin)**: Co-administration can lead to symptomatic hypotension (dizziness, lightheadedness, fainting). If taken together, a lower starting dose of tadalafil and careful monitoring are often recommended (Mayo Clinic).
- **Guanylate Cyclase Stimulators (e.g., riociguat)**: Combining with tadalafil can cause severe hypotension and is therefore contraindicated (FDA label).
- **CYP3A4 Inhibitors (e.g., ketoconazole, ritonavir, erythromycin, grapefruit juice)**: These substances can increase tadalafil levels in the blood, potentially increasing the risk of side effects. Dosage adjustment may be necessary if used concurrently (DrugBank).
- **Alcohol**: Excessive alcohol consumption while taking tadalafil can increase the risk of orthostatic hypotension (a drop in blood pressure upon standing) and enhance symptoms such as headache, dizziness, and increased heart rate (MedlinePlus).
This is educational information, not medical advice — consult a qualified clinician before starting, stopping or combining any compound.
Tadalafil can be taken without regard to meals (FDA label). For 'on-demand' use for erectile dysfunction, it is typically taken at least 30 minutes before anticipated sexual activity. Due to its long half-life (approximately 17.5 hours), the effects of a single dose may last up to 36 hours. For daily use in either erectile dysfunction, benign prostatic hyperplasia, or pulmonary arterial hypertension, it is commonly studied at once daily, at approximately the same time each day (EMA SmPC). Individual needs vary — talk to a licensed clinician to determine an appropriate schedule.
Source for this section: Sources for When should you take Tadalafil?: Jumps to this entry in the sources and references list at the end of the page.
What interacts with Tadalafil?
| Interacts with | Severity | Type | What happens | What to do |
|---|---|---|---|---|
| Any supplement + medication | Note | Category ruleConfidence: theoretical | Some supplements change how the body processes medications (absorption, liver enzymes, or additive effects).Source pending | Specific pairs are checked against a licensed drug database and shown with their own severity. Always confirm with your provider or pharmacist. |
| Any vitamin + medication | Note | Category ruleConfidence: theoretical | Certain vitamins interact with specific medications (e.g., vitamin K with blood thinners).Source pending | Specific pairs are checked against a licensed source; confirm with your provider. |
| Lisinopril | Caution | Compound pairConfidence: theoretical | PDE5 inhibitors add to the blood-pressure-lowering effect of antihypertensives.Source pending | Start PDE5 at the lowest effective dose and monitor for hypotension. |
| Amlodipine | Caution | Compound pairConfidence: theoretical | PDE5 inhibitors add to the blood-pressure-lowering effect of antihypertensives.Source pending | Start PDE5 at the lowest effective dose and monitor for hypotension. |
| Losartan | Caution | Compound pairConfidence: theoretical | PDE5 inhibitors add to the blood-pressure-lowering effect of antihypertensives.Source pending | Start PDE5 at the lowest effective dose and monitor for hypotension. |
| Valsartan | Caution | Compound pairConfidence: theoretical | PDE5 inhibitors add to the blood-pressure-lowering effect of antihypertensives.Source pending | Start PDE5 at the lowest effective dose and monitor for hypotension. |
| Enalapril | Caution | Compound pairConfidence: theoretical | PDE5 inhibitors add to the blood-pressure-lowering effect of antihypertensives.Source pending | Start PDE5 at the lowest effective dose and monitor for hypotension. |
| Ramipril | Caution | Compound pairConfidence: theoretical | PDE5 inhibitors add to the blood-pressure-lowering effect of antihypertensives.Source pending | Start PDE5 at the lowest effective dose and monitor for hypotension. |
| Amantadine | Caution | Compound pairConfidence: theoretical | PDE5 inhibitors lower blood pressure; amantadine can add orthostatic hypotension.Source pending | Rise slowly; monitor BP. Report dizziness or fainting. |
Frequently asked questions about Tadalafil
Tadalafil is a medication. It is also known as Cialis. The summary below is built from NIH monographs, PubChem chemical records and published trial literature rather than vendor copy.
Tadalafil is commonly discussed in the context of supporting mens-longevity. Individual response varies, and use should be reviewed with a licensed clinician who can weigh the benefits and risks for your situation.
For Tadalafil, it is typically taken null and its approximate half-life is 17.5 hours, which influences dosing frequency. Always follow the specific dose your clinician or the product label prescribes.
Tadalafil carries potential side effects and drug interactions, documented in NIH, Mayo Clinic, and FDA label sources. Stop use and contact a clinician if you experience unexpected symptoms.
Interaction risk for Tadalafil comes from the rest of the stack: other medications, prescription medicines, hormone therapy and peptides. With a reported plasma half-life near 17.5 hours, separating doses can change the picture as much as removing one. Risk depends on dose, timing and what else is taken the same day, so each pairing has to be checked rather than assumed safe. The free checker at https://doseroutine.com/interaction-checker covers Tadalafil with no sign-up.
There is no single answer for Tadalafil plus TRT. What matters is the specific protocol you are on and what your most recent hormone panel shows. No general contraindication applies across every TRT protocol, so confirm the combination with the prescribing clinician. See the free TRT interaction reference: https://doseroutine.com/trt-supplement-interactions
Pairing Tadalafil with peptides has to be assessed one peptide at a time, because GLP-1 agonists, secretagogues, healing peptides and melanocortins do not share an interaction profile. Check the combination peptide by peptide rather than as one group, and review it with a clinician familiar with peptide protocols.
With a plasma half-life near 17.5 hours, once-daily dosing is the usual pattern for Tadalafil. Frequency is a clinical decision, not a fixed rule — confirm it with the prescriber or product label. Comparison of apps that keep a schedule like this: https://doseroutine.com/best-dose-tracking-apps
With a plasma half-life near 17.5 hours, a single missed dose of Tadalafil usually has a smaller effect on overall exposure than an irregular pattern of missed doses does. Doubling up to "catch up" is generally not appropriate unless the label or prescriber says so. Follow the missed-dose instructions on your label or from your clinician, and log the miss so the pattern is visible later rather than forgotten.
For Tadalafil the useful record is the dose, the time it was actually taken, and what else was taken in the same window. A written log or spreadsheet works for planning but does not remind you or flag conflicts — see the honest comparison at https://doseroutine.com/vs/spreadsheet and the wider roundup at https://doseroutine.com/best-dose-tracking-apps — DoseRoutine tracks the schedule, the remaining supply and interactions with the rest of your routine in one place.
Both are PDE5 inhibitors, but tadalafil (Cialis) lasts around 36 hours and is absorbed regardless of food, while sildenafil (Viagra) lasts roughly 4–6 hours and is slowed by a fatty meal. Tadalafil is also approved for BPH urinary symptoms; sildenafil is not. Side-effect profiles differ slightly — tadalafil causes more back and muscle ache, sildenafil more visual disturbance. This is educational information, not medical advice.
No. PDE5 inhibitors preserve the nitric-oxide signal that arousal generates; they do not create it. Without sexual stimulation there is no cGMP for the drug to protect, which is why labeling describes it as facilitating rather than causing an erection.
Nitrates and PDE5 inhibitors act on the same nitric-oxide/cGMP pathway from different directions. Together they can cause a severe, sudden drop in blood pressure. FDA labeling makes any nitrate — including recreational "poppers" (amyl nitrite) — an absolute contraindication. This is educational information, not medical advice.
Back and muscle ache appear in roughly 3–6% of users in trial data and are thought to reflect tadalafil's weak inhibition of PDE11, an enzyme found in skeletal muscle. It typically starts 12–24 hours after dosing and resolves within two days. This is educational information, not medical advice.
Which studies looked at Tadalafil?
Peer-reviewed research indexed in PubMed. Each entry links to the original record.
- 1.Tadalafil therapy for pulmonary arterial hypertension(opens PubMed in a new tab)Circulation · 2009 · PMID 19470885 · https://pubmed.ncbi.nlm.nih.gov/19470885/
- 2.Randomized Trial of Macitentan/Tadalafil Single-Tablet Combination Therapy for Pulmonary Arterial Hypertension(opens PubMed in a new tab)J Am Coll Cardiol · 2024 · PMID 38267108 · https://pubmed.ncbi.nlm.nih.gov/38267108/
- 3.Initial combination therapy with macitentan and tadalafil in patients with pulmonary arterial hypertension, with and without cardiac comorbidities(opens PubMed in a new tab)Eur J Heart Fail · 2024 · PMID 38966990 · https://pubmed.ncbi.nlm.nih.gov/38966990/
- 4.Tadalafil(opens PubMed in a new tab)Drugs · 2003 · PMID 14498756 · https://pubmed.ncbi.nlm.nih.gov/14498756/
- 5.Initial Use of Ambrisentan plus Tadalafil in Pulmonary Arterial Hypertension(opens PubMed in a new tab)N Engl J Med · 2015 · PMID 26308684 · https://pubmed.ncbi.nlm.nih.gov/26308684/
Sources cited on this page
Specific documents referenced by the numbered markers above. Each number matches the marker in the text.
- PubChem CID 9821704(opens in a new tab)National Center for Biotechnology Information · pubchem.ncbi.nlm.nih.gov/compound/9821704
Verify at
Publisher search links for Tadalafil. These are places to check the information — they are not citations, so they are not numbered.
- FDA-approved labeling (DailyMed)(publisher search, opens in a new tab)U.S. Food and Drug Administration · publisher search
- DrugBank(publisher search, opens in a new tab)DrugBank Online · publisher search
- Mayo Clinic(publisher search, opens in a new tab)Mayo Clinic · publisher search
- MedlinePlus(publisher search, opens in a new tab)U.S. National Library of Medicine · publisher search
- NIH Office of Dietary Supplements(publisher search, opens in a new tab)National Institutes of Health · publisher search
- Cochrane Library(publisher search, opens in a new tab)Cochrane · publisher search
- Examine.com(publisher search, opens in a new tab)Examine.com · publisher search
- European Medicines Agency(publisher search, opens in a new tab)European Medicines Agency · publisher search
- PubMed literature search(publisher search, opens in a new tab)National Library of Medicine · publisher search
- Wikipedia entry(publisher search, opens in a new tab)Wikipedia · publisher search
DoseRoutine compiles summaries from publicly available scientific and regulatory references. Always verify important decisions with a licensed clinician. How we source and review this information.
What is the short answer on Tadalafil?
Plain-text summary, safe to quote verbatim:
Cialis is the brand name for tadalafil, a PDE5 inhibitor approved for erectile dysfunction, the urinary symptoms of benign prostatic hyperplasia, and pulmonary arterial hypertension (as Adcirca). It blocks the enzyme that breaks down cGMP, so nitric-oxide signaling relaxes smooth muscle and blood flow improves.
Source: DoseRoutine — https://doseroutine.com/library/tadalafil
Cite this page
Using this in an article, AI answer, or research note? Please attribute:
DoseRoutine. (2026). Tadalafil — Overview, Benefits & Side Effects. Retrieved from https://doseroutine.com/library/tadalafil
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