Can I take Doxazosin and Furosemide together?

Why this happens

Both medicines work to lower blood pressure but in different ways. Doxazosin relaxes your blood vessels, while furosemide (a 'water tablet') removes excess fluid from your body. When used together, their effects add up, which can lead to an excessive drop in blood pressure.

Be careful when getting up from a sitting or lying position; move slowly to give your body time to adjust. Your doctor may want to monitor your blood pressure more closely or adjust your doses when starting this combination. If you feel very dizzy or faint, sit or lie down immediately and contact your doctor.

First-dose hypotension

Doxazosin can cause a sudden drop in blood pressure, especially after the very first dose. This may make you feel dizzy or faint when standing up. It is recommended to take your first dose at bedtime to avoid falls.

Cataract surgery

If you are due to have eye surgery for cataracts, you must tell your surgeon you are taking doxazosin. It can cause a complication called 'Floppy Iris Syndrome' which the surgeon needs to prepare for.

Dehydration and electrolyte imbalance

Furosemide can cause severe loss of body water and salts. You must seek medical advice if you develop severe vomiting, diarrhoea, or signs of dehydration like extreme thirst or muscle cramps.

Sulphonamide allergy

If you are allergic to 'sulpha' medicines (such as certain antibiotics like co-trimoxazole), you may also have a serious allergic reaction to furosemide.

Gout

Furosemide can increase the levels of uric acid in your blood, which may trigger a painful gout attack or make existing gout worse.

Alcohol

It is best to avoid or strictly limit alcohol while taking these medicines. Both doxazosin and furosemide lower your blood pressure; alcohol also has this effect. Combining them can cause your blood pressure to drop too low, leading to dizziness, lightheadedness, or fainting, especially when standing up.

Liquorice (Natural/Black)

Avoid eating large amounts of natural black liquorice. It can cause your body to lose potassium and retain salt, which opposes the effect of furosemide and may worsen heart or blood pressure conditions.

Caffeine (Coffee, Tea, Energy Drinks)

Limit your intake of caffeine. Caffeine is a mild diuretic and can increase the water-loss effect of furosemide, potentially increasing the risk of dehydration or electrolyte imbalances.

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.