Can I take Quetiapine and Viagra together?

Why this happens

Both medicines can lower blood pressure. Quetiapine blocks certain receptors (alpha-1) that help control blood pressure, and Viagra (sildenafil) relaxes blood vessels. When used together, these effects add up. Additionally, both drugs can occasionally affect the electrical rhythm of the heart.

Use this combination with caution. If you feel dizzy or lightheaded, sit or lie down immediately. Always stand up slowly from a sitting or lying position. If you experience a painful erection or one that lasts longer than 4 hours, seek emergency medical help immediately. It is best to inform your GP that you are using both of these medications.

Suicidal thoughts and self-harm

Quetiapine can increase the risk of suicidal thoughts or self-harm, particularly in young adults (under 25). You must tell someone you trust or seek medical help immediately if your mood changes or you have thoughts of hurting yourself.

Heart disease (specifically heart rhythm disorders)

Quetiapine can affect your heart rhythm (QT prolongation). This risk is higher if you already have heart disease or take other medicines that affect the heart. Seek immediate medical help if you experience palpitations, fainting, or a racing heartbeat.

Heart conditions and nitrate medications

Never take Viagra if you are using nitrate medicines (like glyceryl trinitrate or isosorbide mononitrate) for chest pain or heart failure. Combining them can cause a dangerous, life-threatening drop in blood pressure.

Priapism (prolonged erection)

If you experience an erection that lasts for more than 4 hours, seek emergency medical attention immediately. Delaying treatment can cause permanent damage to the penis.

Drowsiness and impaired coordination

Quetiapine causes significant drowsiness and can affect your balance. Do not drive or operate machinery until you know how it affects you, and be careful to avoid falls, especially when getting up from a sitting or lying position.

Diabetes and blood sugar control

Quetiapine can cause a significant increase in blood sugar levels, even if you are not diabetic. If you have diabetes, you must monitor your blood sugar more closely as your medication dose may need adjusting.

Dementia in elderly patients

There is an increased risk of stroke and death when quetiapine used to treat dementia-related psychosis in elderly patients.

Alcohol

It is best to avoid or strictly limit alcohol while taking these medicines. Alcohol can increase the sedative effects of quetiapine, making you feel very drowsy or dizzy. When combined with Viagra, alcohol can lower your blood pressure and make it harder to get an erection.

Grapefruit juice

Avoid drinking grapefruit juice or eating grapefruit. It can increase the levels of both quetiapine and sildenafil in your blood, which increases the risk of serious side effects.

Caffeine (Coffee, Tea, Energy Drinks)

Caffeine can interfere with how quetiapine works. It may reduce the effectiveness of the medicine or worsen certain side effects like restlessness. If you consume a lot of caffeine, talk to your doctor before making any sudden changes to your intake, as this can also affect your medicine levels.

High-fat meals

If you are taking the extended-release (XL) version of quetiapine, you should avoid taking it with a very heavy or high-fat meal. This can cause the medicine to be absorbed into your system too quickly (known as 'dose dumping'), which increases the risk of side effects. It is usually best to take it without food or with a light snack.

Taking Viagra with a heavy or high-fat meal (such as a burger or fried food) can delay the medicine from working, meaning it may take longer for you to see an effect.

Taking multiple medicines? Our Medicines Interaction Checker helps you check whether your prescriptions, over-the-counter medicines, and supplements are safe to take together. Simply search for your medicines to see potential interactions and what to do about them.

Disclaimer

This information is for general educational purposes only and should not be relied upon as a substitute for professional medical advice. Always consult your GP, pharmacist, or another qualified healthcare professional before making decisions about your medications. Individual circumstances may vary, and only a healthcare professional who knows your medical history can provide personalised guidance.