# Tadalafil (Cialis): The 36-Hour Option, Daily Dosing and Costs

> Tadalafil lasts far longer than any other ED tablet and is the only one with a licensed daily dose. That changes how sex fits into a relationship. Here is how to choose between the two regimens.

- **Source:** ED Treatment Guides (https://www.edtreatmentguides.com/treatments/tadalafil)
- **Last updated:** 2025-11-18
- **Type:** treatment
- **Category:** Oral medication
- **Prescription:** Prescription only
- **Evidence:** Strong evidence
- **Onset:** 30 minutes – 2 hours
- **Duration:** Up to 36 hours (on-demand) · continuous (daily dosing)
- **Typical US cash cost:** $10–$50 per month (generic) · $70–$90 per tablet (brand Cialis)
- **Best for:** Couples who dislike planning sex around a tablet; Men who also have benign prostatic hyperplasia (BPH); Anyone who wants a daily option rather than an event-driven one
- **Not for:** Anyone taking nitrates or riociguat; Men who get significant back or muscle pain from it; People who want the effect to clear quickly
- **Common side effects:** Headache; Indigestion; Back pain; Muscle aches; Nasal congestion; Facial flushing

## Key points

- Tadalafil's half-life is around 17.5 hours, which gives a useful window of up to 36 hours from a single on-demand dose.
- It is the only PDE5 inhibitor licensed for **daily** low-dose use, which removes the need to plan sex around a tablet entirely.
- It is also approved for benign prostatic hyperplasia, so it can treat two problems with one prescription.
- Food has little effect on absorption — a genuine practical advantage over sildenafil.
- Back and muscle pain is the characteristic side effect, usually appearing 12–24 hours after a dose.

## How tadalafil differs from the rest

Pharmacologically, tadalafil does the same job as sildenafil: it blocks PDE5 so the cyclic GMP produced during arousal survives longer, and blood flow into the penis is sustained. The difference is entirely about how long the molecule stays in the body.

**Why the duration differs**

| Property | Sildenafil | Tadalafil |
| --- | --- | --- |
| Half-life | About 4 hours | About 17.5 hours |
| Useful window | 4–6 hours | Up to 36 hours |
| Effect of food | Fatty meals delay onset | Minimal |
| Daily dosing licensed | No | Yes, 2.5–5 mg |
| PDE6 (retinal) effect | Some — hence the blue tinge | Negligible |
| PDE11 effect | Minimal | Yes — the suspected cause of back and muscle ache |

> **Where the '36 hours' figure comes from**
>
> It is the window during which the drug is still present at levels shown to improve erections in trials — not a claim about how long an erection lasts. You still need arousal, every time.

## Daily dosing vs on-demand

This is the real decision with tadalafil, and it is as much about how you want your relationship to work as about pharmacology.

**Two ways to take the same drug**

|  | On-demand | Daily |
| --- | --- | --- |
| Typical dose | 10 mg (range 5–20 mg) | 2.5 mg or 5 mg every day |
| Timing | At least 30 minutes before sex | Same time each day, sex whenever |
| Frequency limit | No more than once daily | Continuous |
| Best suited to | Sex once or twice a week, or unpredictable schedules | Sex twice a week or more; couples who value spontaneity |
| Steady state reached | N/A | About 5 days |
| Also treats BPH | No | Yes — 5 mg daily is licensed for prostate symptoms |
| Monthly cost (generic) | Often lower — you buy fewer tablets | Often similar, because the daily tablets are low strength |

Daily dosing has one under-appreciated psychological benefit: it decouples the tablet from the sexual event. For men whose ED has a large performance-anxiety component, removing the ritual of 'take pill, now perform' can matter more than the pharmacology. See [daily vs on-demand compared in detail](https://www.edtreatmentguides.com/compare/daily-vs-on-demand).

> **Tip**
>
> If you have both ED and urinary symptoms from an enlarged prostate, raise daily tadalafil with your clinician specifically. One prescription addressing both problems is often cheaper and simpler than two.

## How well it works

Head-to-head evidence puts tadalafil and sildenafil in the same effectiveness bracket — around **60–70%** of men respond, with the same reduction in men who have diabetes or have had prostate surgery. Where studies have asked men to state a preference after trying both, tadalafil usually wins, and the reason given is almost always the longer window rather than a firmer erection.

As with any PDE5 inhibitor, judge it over four to eight attempts at an adequate dose, not over one disappointing evening.

## Side effects

- **Headache** — the most common effect, as with the whole class.
- **Back pain and muscle ache** — characteristic of tadalafil, reported by roughly 1 in 20 men. It typically appears 12–24 hours after a dose, lasts a day or two, and responds to a simple analgesic. If it is persistent, a lower dose or a different molecule usually solves it.
- **Indigestion and reflux**.
- **Nasal congestion and flushing**.
- **Visual side effects are rare** compared with sildenafil, because tadalafil barely touches the retinal enzyme.

> **Get emergency care**
>
> An erection lasting longer than **4 hours** (priapism) is a medical emergency and needs an emergency department, not a phone call. Sudden loss of vision or hearing after a dose also needs same-day medical attention.

> **The long half-life cuts both ways**
>
> If you develop a side effect, it takes longer to clear. And critically: after a dose of tadalafil, at least **48 hours** must pass before nitrate medication can be given safely — double the interval required for sildenafil. Anyone with cardiac disease should weigh that carefully.

## Who should not take it

> **Absolute contraindication**
>
> Never combine any PDE5 inhibitor with nitrate medication — nitroglycerin tablets or spray, isosorbide mononitrate or dinitrate, or recreational 'poppers' (amyl/butyl nitrite). The combination can cause a sudden, dangerous drop in blood pressure. It is also contraindicated with riociguat (Adempas). If you take nitrates for chest pain, tell every prescriber before starting an ED medication. [Read the full safety guide](https://www.edtreatmentguides.com/guides/pde5-safety).

- **Alpha-blockers** — tadalafil is somewhat better tolerated alongside them than other PDE5 inhibitors, but the combination still needs a careful, low starting dose.
- **Strong CYP3A4 inhibitors** — ritonavir, ketoconazole, itraconazole, clarithromycin. Dose reduction and frequency limits apply.
- **Severe kidney or liver impairment** — daily dosing is generally not recommended; on-demand dosing is capped.
- **Recent cardiovascular event** or unstable cardiac disease, until cleared.
- **Previous NAION** or hereditary retinal disease.

## What it costs

Generic tadalafil arrived in the US in 2018 and prices fell sharply. Because the daily regimen uses low-strength tablets and the on-demand regimen uses fewer of them, the monthly cost of the two approaches often lands closer together than people expect.

**Typical US cash prices**

| Route | Typical price |
| --- | --- |
| Generic on-demand, retail pharmacy with a discount card | $10–$40 for 30 tablets |
| Generic daily 5 mg, retail pharmacy with a discount card | $15–$50 per month |
| Generic via telehealth subscription | $15–$45 per month |
| Brand-name Cialis | $70–$90 per tablet |

_US cash estimates as of the update date above. Verify current pricing before buying — see our [cost and insurance guide](https://www.edtreatmentguides.com/guides/cost-and-insurance)._

## Frequently asked questions

### Does tadalafil really last 36 hours?

The drug remains at effective levels for up to about 36 hours in most men, so you can have sex at any point in that window without taking anything else. It does not mean a 36-hour erection, and it does not remove the need for arousal.

### Should I choose daily or on-demand?

If you have sex roughly twice a week or more, or if planning around a tablet is itself part of the problem, daily dosing usually suits better. If sex is less frequent or unpredictable in timing but not in planning, on-demand is simpler and often cheaper.

### Can I switch between the two regimens?

Yes, with your prescriber's guidance. Do not overlap them — starting daily dosing the day after a 20 mg on-demand dose stacks the drug unnecessarily.

### Why does my back hurt the day after?

Tadalafil weakly blocks a related enzyme, PDE11, found in skeletal muscle. That is the leading explanation for the delayed back and muscle ache. It is not dangerous, but if it is bothering you, a lower dose or a different molecule usually fixes it.

### Can I take it with food or alcohol?

Food has minimal effect, which is a practical advantage over sildenafil. Alcohol in moderation is fine; heavy drinking works against you in every respect.

### Is tadalafil safe long term?

Daily tadalafil has been studied and used for years in both ED and BPH with a stable safety profile. Long-term use should still be reviewed periodically with your clinician, particularly if your other medications change.

## Sources

- U.S. Food and Drug Administration. [Drugs@FDA — approved drug products and prescribing information](https://www.accessdata.fda.gov/scripts/cder/daf/)
- American Urological Association. [Erectile Dysfunction: AUA Guideline](https://www.auanet.org/guidelines-and-quality/guidelines/erectile-dysfunction-(ed)-guideline) (2018)
- National Institute of Diabetes and Digestive and Kidney Diseases. [Treatment for Erectile Dysfunction](https://www.niddk.nih.gov/health-information/urologic-diseases/erectile-dysfunction/treatment)
- Cleveland Clinic. [Erectile Dysfunction](https://my.clevelandclinic.org/health/diseases/10035-erectile-dysfunction)

## Related pages

- [Sildenafil (Viagra): How It Works, Dosing, Cost and Side Effects](https://www.edtreatmentguides.com/treatments/sildenafil)
- [Viagra vs Cialis: Which One Should You Try First?](https://www.edtreatmentguides.com/compare/viagra-vs-cialis)
- [Daily vs On-Demand Tadalafil: Which Regimen Fits Your Life?](https://www.edtreatmentguides.com/compare/daily-vs-on-demand)
- [PDE5 Inhibitor Safety: Interactions, Contraindications and Emergencies](https://www.edtreatmentguides.com/guides/pde5-safety)

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_This page is general health information, not medical advice. It cannot account for your own history, medications or risk factors. Talk to a licensed clinician before starting, stopping or changing any treatment._

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