Side Effects of Tadalafil and Apomorphine

Every medicine that changes blood flow or brain signalling can cause unwanted effects, and the two medicines in Curekey's ED treatment work in different ways, so their side effects differ too. Tadalafil acts on blood vessels, which explains why headache, flushing and a blocked nose are its usual complaints. Apomorphine acts in the brain, so nausea and dizziness are the effects most often reported. This page sets out what the trials found for each, what is not yet known about using them together at low doses, and how to tell an annoyance from a reason to get help.

Tadalafil: side effects in once-daily trials

The clearest data come from 12-week trials of tadalafil taken once a day at 2.5 mg or 5 mg, the two approved daily doses. The 3 mg dose in Curekey's treatment sits between them. In those trials, side effects were usually mild, and the rates were not far above placebo [1]:

About 4.1% of men on daily tadalafil stopped because of side effects, compared with 2.8% on placebo [1]. At the higher doses taken only before sex (10 to 20 mg), headache and indigestion were more common, affecting roughly one man in ten [1].

Back pain and muscle aches with tadalafil often start 12 to 24 hours after a dose and tend to ease within a couple of days. They are thought to come from the medicine's effect on blood flow in muscles rather than from any injury.

Apomorphine: side effects at the doses studied for ED

Apomorphine was studied for ED as an under-the-tongue tablet at 2 mg to 4 mg. Nausea was the most common problem. In one large crossover trial, 7.0% of men had nausea on 3 mg, compared with 1.1% on placebo, rising to 14.1% at 4 mg [2]. In a study that stepped men up from 2 mg to 4 mg, nausea affected 9.8%, dizziness 7.1% and headache 6.7%, against 0.4%, 2.4% and 4.0% on placebo [3].

Fainting was the side effect that drew most attention from regulators. Pooled data from several thousand men suggest it was rare at the doses used, but more likely at higher doses [4]. Yawning and drowsiness are listed for apomorphine at the much higher doses used in Parkinson's disease; there are no reliable figures for them at ED doses [5].

What is not known at the combination's low doses

Curekey's tablet contains 3 mg of tadalafil and 1 mg of apomorphine. It is worth being clear about the limits of the evidence:

• 1 mg of apomorphine is below every dose tested for ED. The lowest dose in trials was 2 mg. Side effects with apomorphine rose with dose, so a lower dose may be expected to cause fewer, but this has not been measured.
• No trial has tested tadalafil and apomorphine together at any dose, so there are no side-effect rates for the combination.
• The tablet is compounded, which means it is prepared by a licensed pharmacy for individual patients and has not been reviewed by the FDA for safety or effectiveness [6].

In practice, the side effects most worth watching for are those of each ingredient: headache, flushing, indigestion or a stuffy nose from tadalafil, and nausea or lightheadedness from apomorphine. If you notice something not listed here, tell your care team; reports from patients are part of how a physician judges whether a treatment suits you.

Rare but serious effects

A few effects are uncommon but need prompt action:

• Prolonged erection (priapism). An erection lasting more than four hours can damage the penis permanently if not treated [1].
• Sudden vision loss. Rare cases of a type of optic nerve damage called NAION have been reported in men taking PDE5 inhibitors such as tadalafil. A direct cause has not been proven, but men who have had it before, or who have a "crowded" optic disc, may be at higher risk [1].
• Sudden hearing loss. Sudden decrease or loss of hearing, sometimes with ringing or dizziness, has been reported [1].
• Fainting or a sharp fall in blood pressure. This is most likely when the medicine is combined with nitrates, poppers, alcohol in large amounts, or certain blood pressure medicines. Our safety guide lists the combinations to avoid.
• Allergic reactions such as a rash, swelling of the face or lips, or trouble breathing.

Managing the milder ones

Most mild side effects fade as the body adjusts over the first one to two weeks. Some practical steps that may help:

• Headache: drink enough water and limit alcohol. An over-the-counter pain reliever is often fine, but check with a pharmacist if you take other medicines.
• Indigestion: a light meal and avoiding lying down straight after taking a dose may help.
• Flushing or stuffy nose: these usually pass within hours and rarely need treatment.
• Nausea: a small snack and sipping water may help. Do not reach for ondansetron or similar anti-nausea medicines without checking with a clinician first, because that drug class is not safe with apomorphine.
• Lightheadedness: sit or lie down until it passes, stand up slowly, and avoid driving or using machinery until you know how the medicine affects you.

Do not take extra doses, change how you take the tablet, or stop and restart repeatedly without guidance. Follow the directions on your prescription label.

Message the care team, or get urgent help?

Message your care team if a mild side effect lasts more than a couple of weeks, keeps coming back, or makes you less likely to keep taking the treatment. The physician can review whether the plan still suits you.

Get emergency care straight away (call 911 or go to an emergency department) for an erection lasting over four hours, sudden changes in vision or hearing, chest pain, fainting, or signs of a severe allergic reaction.

Sources

1. Tadalafil US prescribing information (DailyMed, revised 2026)
2. Dula E, et al. Double-blind crossover comparison of 3 mg apomorphine SL with placebo and with 4 mg. Eur Urol, 2001
3. von Keitz AT, et al. Forced dose-escalation study of apomorphine SL. BJU Int, 2002
4. Bukofzer S, Livesey N. Safety and tolerability of apomorphine SL. Int J Impot Res, 2001
5. Apomorphine sublingual film prescribing information (FDA, 2020)
6. FDA. Compounding and the FDA: questions and answers

Related reading

• Is ED medication safe for you?: nitrates, heart conditions and medicine interactions to check first.
• How tadalafil works: what the medicine does and why daily doses are used.
• What apomorphine is: how a brain-acting medicine supports erections.
• The tadalafil and apomorphine combination: the reasoning and the gaps in the evidence.
• Erectile dysfunction overview: causes, treatment options and when to see a doctor.

This article is for education only and is not a substitute for professional medical advice. Do not start, stop or change a medication without speaking to a licensed clinician. If you have chest pain, an erection lasting more than four hours, or sudden loss of vision or hearing, seek emergency care.