How do medicines work?

Even the healthiest of us needs a helping hand now and again, and more and more of us take medicines to reduce the risk of future medical problems as well as to treat symptoms.

You must have seen all the hoo-ha in the media in recent years about the threat of our antibiotics becoming useless. It may be scary, but it could just happen - more and more bacteria are becoming resistant to antibiotics. The good news is that we're fighting back. Smarties are just as likely to 'cure' a viral infection as antibiotics are, and they have fewer side effects (except for your waistline). That's why your doctor won't prescribe antibiotics unless he's confident you have a bacterial infection. The more we take, the more resistance grows. But not taking a full course of antibiotics, even if you feel better, can also lead to resistance - and the chance the infection will come back.

I have a confession. Nobody actually knows exactly how antidepressants work - although we think they act partly to top up your natural levels of chemical messengers inside the brain. They don't speed up or slow down recovery. Depression often settles within six months or so - which is why doctors recommend you stick with antidepressants for at least six months after you feel better (or longer if it's not the first time you've been depressed). If you keep taking them once the depression has gone, you won't feel any different. So the only way to be sure if you're feeling fine because your depression has settled, rather than because of the tablets, is to stop them. But don't do this without discussing it with your doctor. Coming off antidepressants too fast can cause side effects, so take advice from them about how to tail them off to minimise problems.

Lots of my patients are worried about side effects from steroids. They're widely prescribed for conditions from asthma to eczema to diseases caused by an overactive immune system, because they damp down inflammation. In high doses they can increase blood pressure and blood sugar, cause weight gain and thin your skin and bones. But the dose of steroids in creams and inhalers is tiny compared to the dose in tablets, because they're applied or delivered straight to where they're needed. That means very little is absorbed into the rest of your body, and side effects are uncommon unless you use stronger topical steroids for long periods.

In the same way that food goes off, medicines change over time - especially once the sealed box or tube is opened. Expiry dates are there for a reason! Never use medicines that are past their expiry date or have been open too long. At best, they're likely to be less effective - at worst they may be contaminated with germs.

Lots of medicines have drowsiness as a side effect. Most of them are recommended before bedtime. Simvastatin - a commonly prescribed cholesterol-lowering medicine - should be taken at bedtime not because of drowsiness, but because it isn't absorbed into your system as well at other times. The most commonly prescribed alternative, atorvastatin, can be taken at any time of day.

The majority of medicines are broken down in your liver or removed from your body through your kidneys. Side effects like feeling sick, tummy pain and diarrhoea are often worse when levels reach their peak in your blood. 'Slow release' versions of a medicine are absorbed into (and removed from) your system more slowly. This smooths out the peak levels in your bloodstream, which may help reduce side effects.

Your pharmacist is your best ally! They can advise on interactions between drugs, how to take them and much more. It's important to remember that even 'natural' remedies like herbal medicines can have side effects, and can interact with other tablets you take. Do tell your pharmacist about all the tablets you take, not just the prescribed ones. It's always better if possible to speak to your doctor or pharmacist before stopping your medicine - you've been given it for a reason

Lots of my patients feel sick with some of the medication I prescribe (it makes me very unpopular, but I don't do it on purpose, I promise!). Often, taking medicines with food will slow down the rate they're absorbed into your bloodstream. This can reduce side effects. However, some medicines (like the antibiotic flucloxacillin) don't work as well if they're taken with food.

With thanks to 'My Weekly' magazine where this article was originally published.

Disclaimer: This article is for information only and should not be used for the diagnosis or treatment of medical conditions. Patient Platform Limited has used all reasonable care in compiling the information but make no warranty as to its accuracy. Consult a doctor or other health care professional for diagnosis and treatment of medical conditions. For details see our conditions.