Tadalafil (Cialis): How It Works, How Long It Lasts, When to Take It

Tadalafil is one of the medicines I discuss with patients most often, both with men who have erection problems and with men aged 40–60 who also have urinary symptoms from an enlarged prostate. The best-known brand name is Cialis, but in Thailand there are several generic brands containing the same active drug. This article explains how the medicine works and how to use it safely.

How tadalafil works

Tadalafil belongs to the PDE5 inhibitor group. When you are sexually aroused, your body produces a substance called cGMP, which relaxes the blood vessels in the penis so blood can flow in. The PDE5 enzyme breaks cGMP down. The medicine helps cGMP last longer, so erections come more easily and hold better.

It is important to understand that the medicine does not cause an erection on its own. You still need arousal and sexual stimulation, and it does not increase sex drive. If the main problem is a lack of desire, hormones, stress or your relationship should be looked at, for example symptoms of low testosterone.

1. 1Sexual arousalThe pill does not cause an erection by itself; arousal is needed first
2. 2Body makes cGMPPenile blood vessels relax and blood flows in
3. 3Drug blocks PDE5PDE5 normally breaks down cGMP, so the drug helps it last
4. 4Easier, longer erectionErections come more easily and last better

Tadalafil does not increase sexual desire.

Its standout feature: it can work for up to 36 hours

Tadalafil has a half-life of about 17.5 hours, much longer than sildenafil. The advantages patients often mention are:

1. No need to rush. You don't have to time sex to a particular hour.
2. It feels more natural. Intimacy can happen at the couple's own pace.
3. It covers a long window, for example from Friday evening to Saturday morning.
4. A low daily dose is possible for some men.

Food has little effect on how it is absorbed, but avoid heavy drinking, because alcohol both makes erections harder and increases the chance of low blood pressure.

How it is used (as assessed and prescribed by a doctor)

On demand

Taken before sexual activity, generally at least 30 minutes to 1–2 hours beforehand. Common doses are 10 or 20 mg, and it should not be taken more than once a day. This suits men who have sex less often. Read more in Tadalafil 10 mg vs 20 mg: what's the difference?

Low daily dose

2.5–5 mg once a day at the same time each day. Blood levels become steady after about 5 days of continuous use. This suits men who have sex regularly, don't want to plan ahead, or also have an enlarged prostate (the dose used for an enlarged prostate is 5 mg a day). See the comparison in Daily vs on-demand tadalafil.

The dose may need to be lower in men with reduced kidney or liver function, or who take certain other medicines. This is why a doctor needs to assess you first.

On demand

As needed

• Taken at least 30 minutes to 1-2 hours before sex
• Commonly 10 or 20 mg
• No more than once a day
• Suits people who have sex less often

Low daily dose

Daily use

• 2.5-5 mg once a day, same time
• Steady drug level after about 5 days
• Suits people with regular activity
• Also helps enlarged prostate symptoms

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Dose and pattern are as assessed by your doctor. A lower dose may be needed with reduced kidney or liver function.

Possible side effects

• Headache, flushing, stuffy nose
• Indigestion, heartburn
• Back pain or muscle aches, which are more common with tadalafil than with other drugs in the group. They usually appear 12–24 hours after a dose and settle on their own.
• Dizziness from a slight drop in blood pressure

Most side effects are mild and lessen with continued use. If they bother you a lot, tell your doctor so the dose can be adjusted or the medicine changed.

Contraindications and medicines to be careful with

• Riociguat, used for pulmonary hypertension, must not be used together with it.
• Alpha-blockers for blood pressure (including some prostate medicines) can be used with it, but low blood pressure is a risk.
• Strong CYP3A4 inhibitors, such as some antifungals and HIV medicines containing ritonavir or cobicistat, raise tadalafil levels, so the dose must be reduced.
• Men with severe heart disease, a recent heart attack or stroke, or very low blood pressure need a doctor's assessment first.

Read more about the dangers of poppers in Poppers: what they are and the risks you need to know.

Symptoms that mean going to hospital immediately

• An erection lasting more than 4 hours (priapism), which risks permanent tissue damage
• Chest pain or tightness, fainting or nearly fainting
• Sudden blurred vision or loss of vision in one eye
• Sudden loss of hearing or severe ringing in the ears

Why you shouldn't buy it and take it yourself

These medicines need a doctor's assessment, because your heart, your other medicines and the cause of your ED all need checking, and ED may be a sign of diabetes or high blood pressure you don't yet know about. Medicines sold online also carry the risk of being fake or not containing the dose on the label.

At Dr. Kris Clinic we assess your symptoms, look for related causes such as low testosterone, diabetes or stress, and then choose the form of treatment that suits your body and lifestyle, in person in Surat Thani or online, with consultations in English available. For the overall treatment picture, read Erectile dysfunction (ED).