Can I take Guanfacine and Tizanidine together?

Why this happens

Both guanfacine and tizanidine are 'alpha-2 agonists'. This means they work in a similar way to relax blood vessels and slow down the nervous system. When used together, their effects add up, leading to a much stronger impact on blood pressure, heart rate, and alertness than either drug would have on its own.

What you should do

You should speak to your doctor before taking these medicines together. If your doctor decides you need both, they may start you on a lower dose and monitor your blood pressure and heart rate closely. Avoid driving or operating machinery until you know how this combination affects you. Get up slowly from a sitting or lying position to prevent dizziness.

Important precautions

Low blood pressure and heart rate

Both medicines can significantly lower your blood pressure and heart rate. Do not stop taking them suddenly, as this can cause a dangerous 'rebound' spike in blood pressure and a rapid heartbeat. Always taper the dose gradually under medical supervision.

Liver impairment

Tizanidine can cause serious liver damage. You must have regular blood tests to check your liver function, especially during the first few months of treatment. Seek immediate medical help if you notice yellowing of the skin or eyes.

Severe drowsiness and sedation

These medicines cause significant drowsiness that is much stronger when they are taken together or with alcohol. This can severely impair your ability to drive or operate machinery safely.

Stopping treatment suddenly

Do not stop taking tizanidine suddenly. Doing so can cause a rapid rise in blood pressure and heart rate. Your dose must be reduced gradually.

Food and drink warnings

Alcohol

It is best to avoid or strictly limit alcohol while taking these medicines. Both guanfacine and tizanidine cause drowsiness and can lower your blood pressure. Alcohol will significantly increase these effects, making you feel very dizzy, sleepy, or lightheaded, and increasing the risk of falls or accidents.

High-fat meals

Taking this medicine with a high-fat meal can significantly increase the amount of medicine absorbed into your bloodstream. This increases the risk of side effects like low blood pressure, slow heart rate, and extreme sleepiness. You should take it at the same time each day, either with or without food, but avoid high-fat meals at the time of dosing.

Grapefruit juice

Grapefruit juice can stop your body from breaking down guanfacine properly. This can lead to higher levels of the medicine in your blood, increasing the risk of side effects. Avoid drinking grapefruit juice while taking this medicine.

Caffeine (Coffee, Tea, Energy Drinks)

You should avoid or strictly limit caffeine while taking tizanidine. Caffeine can interfere with how your body breaks down this medicine, leading to higher levels of tizanidine in your blood. This can increase the risk of side effects like low blood pressure, a slow heart rate, and extreme sleepiness.

Using other medicines

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.