With some 8500 conventional drugs on the market, it's difficult to bear all possible interactions in mind. So, here in brief is what you need to know of the main adverse reactions related to the most commonly used medications.
- Atorvastatin. Used to lower cholesterol, taking vitamin B3 (niacin; also in vitamin B complex) at the same time could bring on muscle weakness and dysfunction.
- Acetylsalicylic acid (aspirin). Its blood-thinning effects last three days, so never take aspirin-containing medication within three days of surgery, botox or tooth extraction. Taking an anti-inflammatory at the same time will increase the risk of stomach bleeds 10-fold.
- Azathioprine. An immunosuppressant used for inflammatory bowel disease and rheumatoid arthritis, this is not be taken with the gout prophylactic allopurinol (Zyloric), which halts azathioprine metab-olism, causing life-threatening anaemia.
- Celecoxib. A painkiller for osteoarthritis, rheumatoid arthritis and ankylosing spondylitis, taking it with any antiplatelet (blood-thinning) drug substantially raises the risk of haemorrhage.
- Dextromethorphan. Found in Vicks products, and in over-the-counter cough and cold remedies, taking this with mono-amine oxidase inhibitors, such as tranyl-cypromine, for depression and Parkin-son's may result in agitation with fever.
- Diclofenac and ibuprofen. Used to treat pain and inflammation, and as part of a complex medication (such as Nurofen Cold & Flu), gastrointestinal ulceration and bleeding are common; there is also a small risk of erectile dysfunction.
- Indomethacin. Another painkiller often given for joint disease, this reduces the blood-pressure-lowering action of diur-etics, beta-blockers and ACE inhibitors, thus increasing the risk of cardiovascular events.
- Loperamide. Used against diarrhoea, one tablet works over three days, and taking quinidine, a cardiac antiarrhythmic, at the same time leads to a two- or threefold increase of loperamide in the blood, causing abdominal cramps, dizziness, urticaria (rash), drowsiness and intestinal obstruction (paralytic ileus).
- Metformin. Prescribed for diabetes, taking blood-thinners (acenocoumarol, nicocoumalone, warfarin) at the same time leads to a greater risk of stroke.
- Methotrexate. An immuno-suppressant used to induce abortion in early pregnancy, this lowers the white-blood-cell count, so predisposing to infections, fatigue and other symptoms resembling HIV infection.
- Naproxen. An anti-inflammatory used for rheumatic, gouty and arthritic condi-tions, when cortisone preparations are taken at the same time, the risk of a stomach ulcer is significantly increased.
- Pantoprazole. Taken for duodenal ulcers and gastroesophageal reflux, but at the same time as the blood-thinning drug clopidogrel, pantoprazole inhibits the blood-thinning action of the latter.
- Paracetamol. Biodegraded over two days, taking phenobarbital (say, for insomnia) at that time should be avoided because of a risk of liver damage. Those taking anti-epileptic medications containing phenobarbital need to abstain from paracetamol altogether.
- Prednisolone. Used to suppress inflammatory disorders, this affects the stomach when taken with long-term medications for rheumatoid conditions. When an antiplatelet drug is added to the mix, the result can be internal haemorrhage.
- Pregabalin. Used for chronic pain such as diabetic neuropathy, fibromyalgia, post-herpetic neuralgia and spinal discopathy, this drug (marketed as Lyrica) is one of four drugs for which a Pfizer subsidiary pleaded guilty to misbranding "with the intent to defraud or mislead". Pfizer agreed to pay the colossal sum of $2.3 billion (lb1.4 billion) in settlement. Pregabalin also substantially intensifies the effects of psychotropic benzodiaze-pines, such as lorazepam, by increasing their hypnotic and especially their amnesic effects (causing memory loss).
- Simvastatin. Taken to reduce cholesterol levels, when taken together with antibiotics such as erythromycin and clarithromycin, serious muscle and kidney damage may ensue.