What is the potential problem?
Taking certain medicines when you are dehydrated can result in you developing a more serious illness. The ‘Medicine Sick Day Rules’ lists medicines that should be temporarily stopped during a dehydrating illness.
ACE inhibitors: a medicine for high blood pressure and heart conditions. If you are dehydrated, these medicines can stop your kidneys working properly.
Examples: names ending in ‘pril’ such as lisinopril, perindopril, ramipril
ARBs: a medicine for high blood pressure and heart conditions. If you are dehydrated, these medicines can stop your kidneys working properly.
Examples: names ending in ‘sartan’ such as losartan, candesartan, valsartan
Diuretics: sometimes called ‘water pills’ for excess fluid and high blood pressure. These medicines can make dehydration more likely.
Examples: furosemide, bendroflumethiazide, indapamide, spironolactone
Metformin: a medicine for diabetes. Dehydration can make it more likely that you will develop a serious side effect called lactic acidosis.
NSAIDs: anti-inflammatory pain killers. If you are dehydrated, these medicines can stop your kidneys working properly.
Examples: ibuprofen, naproxen, diclofenac
Which illnesses cause dehydration?
Dehydration is the loss of fluid from your body. Vomiting, diarrhoea and fever (high temperature, sweats, shaking) can make you dehydrated. If you are sick once or have diarrhoea once, then you are unlikely to become dehydrated. Having two or more episodes of vomiting or diarrhoea can lead to dehydration: in these cases, you should follow the advice on this page.
What actions should I take?
If you develop a dehydrating illness, you should temporarily stop taking any medicine listed on this page and any other medicine identified by your health professional. It is very important that you restart your medicine once you have recovered from the illness. This would normally be after 24 to 48 hours of eating and drinking normally. When you restart your medicine, just take them as normal. Do not take extra for the doses you have missed.
This information is taken from https://ihub.scot/media/1401/20180424-web-medicine-sick-day-rules-patient-leaflet-web-v20.pdf