Tadalafil and Olanzapine: Can They Be Taken Together?

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What is tadalafil and olanzapine used for?

Tadalafil is a prescription medicine used to treat erectile dysfunction (ED) in men [4]. It belongs to a group of medicines called PDE5 inhibitors, which work by relaxing blood vessels in the penis, allowing increased blood flow when you are sexually aroused. Tadalafil is the active ingredient in branded Cialis and is available as a generic medicine in the UK. It can be taken on-demand (10 mg or 20 mg at least 30 minutes before sex, with effects lasting up to 36 hours) or as a daily low dose (2.5 mg or 5 mg) [4].

Olanzapine is an antipsychotic medicine used to treat conditions such as schizophrenia and bipolar disorder [12]. It works by affecting certain chemicals in the brain, particularly dopamine and serotonin, helping to stabilise mood and reduce symptoms like hallucinations, delusions, or mania. Olanzapine is usually taken once daily, and the dose varies depending on the condition being treated and individual response. Like many antipsychotic medicines, olanzapine can cause side effects including weight gain, drowsiness, and changes in blood pressure [12].

Is there an interaction between tadalafil and olanzapine?

There is no well-documented major direct interaction between tadalafil and olanzapine reported in standard UK prescribing references [3][4][12]. This means that many men taking olanzapine can use tadalafil for erectile dysfunction, provided their prescriber has reviewed their full medical history and current medicines. However, both medicines can affect blood pressure, which is an important consideration.

Tadalafil lowers blood pressure slightly by relaxing blood vessels throughout the body, not just in the penis [4]. Olanzapine can also cause changes in blood pressure, including low blood pressure (hypotension) or dizziness, particularly when standing up quickly (postural hypotension) [12]. When two medicines that can both lower blood pressure are taken together, there is a theoretical risk that the combined effect could cause symptoms such as dizziness, light-headedness, or fainting, especially when moving from sitting to standing.

This does not mean the combination is unsafe for everyone, but it does mean your prescriber will need to assess your individual risk. They will consider factors such as your usual blood pressure, whether you experience dizziness with olanzapine, any other medicines you take, and your overall cardiovascular health. Most men taking a stable dose of olanzapine can use tadalafil without problems, but the assessment must be personalised.

How the interaction works in plain English

Think of blood pressure as the force pushing blood through your arteries. Tadalafil relaxes the walls of blood vessels, making it easier for blood to flow and slightly reducing the pressure. Olanzapine can also affect the nervous system's control of blood pressure, sometimes causing it to drop, particularly when you stand up. If both medicines are working at the same time, the combined blood-pressure-lowering effect might be more noticeable in some people, leading to dizziness or feeling faint. This is why your prescriber checks your blood pressure, asks about any dizziness you've experienced, and may start you on a lower dose of tadalafil if needed.

When to get urgent help

• Erection lasting longer than 4 hours (priapism) – call 999 or go to A&E immediately
• Sudden loss of vision in one or both eyes – seek urgent medical help
• Sudden decrease or loss of hearing, possibly with ringing in the ears – seek urgent medical help
• Chest pain during or after sex – stop activity, call 999, and tell them you have taken tadalafil
• Severe dizziness, fainting, or very fast/irregular heartbeat – seek same-day GP advice or call NHS 111

Call 999 or go to A&E in an emergency, or contact NHS 111 for urgent advice.

What does your prescriber check before prescribing tadalafil with olanzapine?

When you request tadalafil through an online consultation at Cured Pharmacy or see your GP, the prescriber will ask about all your current medicines, including olanzapine, and review your medical history [1][2]. They will specifically check your blood pressure (or ask when it was last measured), whether you experience dizziness or fainting, and whether you have any heart or circulation problems. If you take other medicines that lower blood pressure—such as medicines for high blood pressure, alpha-blockers for prostate symptoms, or other antipsychotics—the prescriber will assess the combined risk carefully.

The prescriber will also check for any absolute contraindications to tadalafil, such as use of nitrates (GTN spray, isosorbide mononitrate or dinitrate), nicorandil, riociguat, or recreational drugs called 'poppers' (amyl or alkyl nitrites) [4]. Do not take tadalafil together with any of these medicines or substances, as the combination can cause a dangerous fall in blood pressure. If you are taking any potent CYP3A4 inhibitors (such as ritonavir, ketoconazole, itraconazole, or clarithromycin), the prescriber will adjust the tadalafil dose or consider whether it is suitable, as these medicines can raise tadalafil levels in the blood [4].

The prescriber will also consider whether sexual activity is safe for you. Tadalafil is not suitable if you have had a recent heart attack or stroke, have unstable angina, severe heart failure, very low blood pressure, or certain eye conditions such as previous sudden vision loss (NAION) [4]. If you have any concerns about your heart health or blood pressure, discuss them openly during your consultation—erectile dysfunction can sometimes be an early warning sign of cardiovascular disease, and your GP can arrange further checks if needed [1][2].

Practical advice for taking tadalafil and olanzapine together

If your prescriber approves tadalafil while you are taking olanzapine, there are several practical steps you can take to use it safely. First, take tadalafil exactly as prescribed—do not take more than the recommended dose or use it more often than once a day (for on-demand doses) [4]. If you are prescribed the 10 mg or 20 mg on-demand dose, take it at least 30 minutes before you plan to have sex; the effect can last up to 36 hours, so you do not need to rush. If you are on daily tadalafil (2.5 mg or 5 mg), take it at the same time each day, regardless of when you plan sexual activity [4].

Be cautious when standing up, especially in the first few hours after taking tadalafil, as this is when the blood-pressure-lowering effect is strongest. If you feel dizzy or light-headed, sit or lie down until the feeling passes, and avoid driving or operating machinery until you know how the combination affects you. Limit alcohol while using tadalafil, as heavy drinking can worsen erectile dysfunction, increase the risk of side effects, and add to the blood-pressure-lowering effect [4]. Grapefruit juice can raise tadalafil levels in the blood, so it is best to avoid it [4].

Do not stop or change your olanzapine dose without speaking to the doctor who prescribed it, even if you experience side effects. Olanzapine is an important medicine for managing your mental health, and stopping it suddenly can cause withdrawal symptoms or a relapse of your condition. If you think olanzapine is contributing to erectile dysfunction (some antipsychotic medicines can affect sexual function), talk to your psychiatrist or GP—they may be able to adjust your treatment. Never take tadalafil alongside another PDE5 inhibitor (such as sildenafil or vardenafil) or with nitrates, nicorandil, riociguat, or poppers [4].

Starting on a lower dose

Your prescriber may suggest starting with a lower dose of tadalafil (such as 10 mg on-demand or 2.5 mg daily) to see how you tolerate it while taking olanzapine [4]. This cautious approach allows you and your prescriber to assess whether you experience any dizziness or other side effects before considering a higher dose. If the lower dose is effective and well tolerated, there may be no need to increase it. If it is not quite enough, your prescriber can review and adjust the dose at a follow-up consultation, provided your blood pressure and overall health remain stable.

At a glance

Warning signs and when to seek help with tadalafil and olanzapine

Most men taking tadalafil and olanzapine together do not experience serious problems, but it is important to know the warning signs that need urgent attention. Seek immediate medical help (call 999 or go to A&E) if you experience an erection that lasts longer than four hours (priapism), even if it is not painful [4]. Priapism is a medical emergency that requires urgent treatment to prevent permanent damage to the penis. Also seek urgent help if you have sudden loss of vision in one or both eyes, or sudden decrease or loss of hearing, which may be accompanied by ringing in the ears or dizziness [4].

If you develop chest pain during or after sexual activity, stop and seek medical help immediately—do not take nitrate medicines (such as GTN spray) if you have used tadalafil in the past 48 hours, as the combination can cause a dangerous drop in blood pressure [4]. Tell the paramedics or doctor that you have taken tadalafil. If you experience severe dizziness, fainting, or a very fast or irregular heartbeat, seek same-day medical advice from your GP or call NHS 111.

Common side effects of tadalafil include headache, indigestion, back pain, muscle aches, flushing, and a blocked or runny nose [4]. These are usually mild and go away on their own. If side effects are troublesome or persistent, contact your prescriber—they may be able to adjust your dose or suggest an alternative treatment. If you develop new or worsening symptoms while taking olanzapine (such as increased dizziness, confusion, or changes in mood), contact the doctor who prescribed it as soon as possible.

Other erectile dysfunction treatments and olanzapine

If tadalafil is not suitable or effective for you, there are other licensed treatments for erectile dysfunction available in the UK [1][2]. Sildenafil (generic Viagra) is another PDE5 inhibitor that works in a similar way to tadalafil but has a shorter duration of action—about four to six hours [3]. It is taken about one hour before sex and is available in 25 mg, 50 mg, and 100 mg doses. Like tadalafil, sildenafil can lower blood pressure, so the same precautions apply when taking it with olanzapine: your prescriber will assess your individual risk and may start you on a lower dose.

Other PDE5 inhibitors include vardenafil (generic Levitra), which is taken 25 to 60 minutes before sex and lasts about four to five hours [5], and avanafil (Spedra), which works faster (15 to 30 minutes) and is cleared from the body more quickly [6]. All PDE5 inhibitors have similar interactions and precautions, so if you are taking olanzapine, the same careful assessment applies regardless of which PDE5 inhibitor you choose. Your prescriber will help you decide which medicine and dose are most suitable based on your lifestyle, how often you plan to have sex, and your response to treatment.

If oral tablets are not suitable, other options include alprostadil cream (Vitaros) applied to the tip of the penis, or alprostadil injections (Caverject) into the side of the penis [7]. These work by a different mechanism and do not have the same blood-pressure interactions as PDE5 inhibitors, but they require training and are usually considered if tablets have not worked. There is also a topical gel called Eroxon, which is a medical device available without prescription. Your GP or a specialist can discuss all the options with you and refer you to a urology or sexual health service if needed [1][2].

Can I use Viagra Connect or Cialis Together from a pharmacy?

Viagra Connect (sildenafil 50 mg) and Cialis Together (tadalafil 10 mg) are pharmacy medicines available without a prescription after a consultation with a pharmacist in a registered pharmacy [1]. However, if you are taking olanzapine or any other prescribed medicine, you must tell the pharmacist during the consultation. The pharmacist will assess whether it is safe for you to buy the medicine over the counter or whether you should see your GP or use a prescription service for a fuller assessment. In many cases, men taking medicines like olanzapine are advised to use a prescription service (such as Cured Pharmacy's online consultation) so that a prescriber can review your full medical history and current medicines in detail before approving treatment.

In summary

• No major direct interaction between tadalafil and olanzapine is commonly reported in clinical practice
• Both medicines can lower blood pressure, so your prescriber will assess your individual risk carefully
• Most men on stable olanzapine can use tadalafil safely, often starting on a lower dose
• Tell your prescriber about all medicines you take, including olanzapine and any other antipsychotics
• Seek urgent help if you have an erection lasting over 4 hours or sudden vision or hearing loss

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