Taking medicines safely

Written by: 
Steve Chaplin, medical writer

Taking medicines safely

There is a mass of information about medicines. How can you decide what's really important?

There is no simple answer: factors that are critical for one medicine may not matter much for others. So it is important to be careful about where you get your information from and how you use it.

Included on this page:

What information can I trust?

If you have a question about your medicine, there are several sources of information:

  • The patient information leaflet (PIL) or package insert that usually comes with your medicine aims to tell you everything you need to know about taking the medicine. It is included in the packaging with branded and non-branded (generic) medicines in many countries, but may not be provided with traditional or complementary medicines (such as herbal or homeopathic products)
  • Many manufacturers have a telephone helpline for patients. The number may be provided on the PIL or packaging of your medicine
  • If the PIL or helpline cannot answer your question, a health professional, such as your doctor, nurse or pharmacist, is the best person to provide information that applies specifically to you.

When to take a medicine

You might want a medicine to act at a particular time - for example, you wouldn't take a sleeping pill in the morning, unless you were doing shift work. Some medicines aren't reliable unless they're taken at the same time each day, for example the progestogen-only contraceptiveA term used to describe something that prevents pregnancy. pill (mini-pill). Some medicines need to be taken before or after a meal - food can increase or reduce the amount absorbed from the stomach - whereas for others the effect of food is not important. Food can reduce the likelihood of some side effects: if you take aspirin with food, you are less likely to get indigestionDiscomfort after eating..

How to take a medicine

Most people take a tablet or capsule with water because it's easier to swallow; this also helps to move the tablet into the stomach. But not all liquids are equally good for this purpose. Some medicines shouldn't be taken with grapefruit juice, as it affects the body's processing of the drug, for example, some calciumAn element that forms the structure of bones and teeth and is essential to many of the body's functions. channel blockers (taken for high blood pressure The pressure of blood within the arteries.- hypertensionHigh blood pressure.) and some statinsA class of drugs that inhibit cholesterol formation in the liver. (used to lower cholesterolA substance present in many tissues and an important constituent of cell membranes although high concentrations of a certain type of cholesterol in the blood are unhealthy.). The effects of the anticoagulantA medication that prevens blood from clotting, or which reduces the likelihood of the blood to clot. warfarin (taken to reduce clotting, or to 'thin the bloodA fluid that transports oxygen and other substances through the body, made up of blood cells suspended in a liquid.') are increased by cranberry juice, making accidental bleeding more likely.

If you lie down after taking a tablet there is a chance that it could get stuck in the throat, and some medicines can cause damage to the oesophagusThe gullet, the part of the gastrointestinal system that extends down from the mouth cavity to the stomach. in this situation. For example, if you have osteoporosis and you take a bisphosphonate like alendronate, you take it after getting up in the morning and then remain standing or sitting upright for at least 30 minutes.

How much to take

It's important never to take more than the prescribed or recommended dose of any medicine.

The dose you are prescribed of a prescription medicine, or the recommended dose of an over-the-counter medication, is a balance between maximising the good and minimising the bad effects of a medicine. If you increase the dose, you can change the balance in favour of side effects. In some cases, higher doses make the side effects worse without any extra benefit. For a few medicines, like theophylline (used to treat asthma and chronicA disease of long duration generally involving slow changes. bronchitis) and the anti-epileptic drug phenytoin, side effects can quickly become severe with small increases in dose.

Stopping a medicine

It is not sensible to stop taking any prescribed medicine without consulting your doctor. While it may be safe to just stop taking some medicines without doing yourself any immediate harm, this is not true for all medicines. Therefore it is important to consult your doctor before stopping taking any drug that has been prescribed for you.

You might want to stop taking a medicine if you think that it is causing side effects. In this case, talk to your doctor, nurse or pharmacist as soon as you can - preferably before changing the way you take the medicine. You might be advised that it is all right to take a lower dose instead of stopping.

In addition, it's important to be aware that when you stop taking a medicine, you lose the benefit of treatment. This is important. For example, a medicine that reduces stomach acid (a proton pump inhibitor or PPI) is often prescribed to prevent an NSAID (non-steroidal anti-inflammatoryAny drug that suppresses inflammation drug) causing a stomach ulcer Any abnormal break in the epithelium, the outer layer of cells covering the open surfaces of the body.- if you stop taking it, the risk that the NSAID will harm your stomach increases. Some medicines can cause side effects if you stop taking them suddenly. Examples include benzodiazepines such as diazepam, which are used to combat anxiety,  and some antidepressants such as fluoxetine  and citalopram. If you want to stop, you'll need to reduce the dose over a few weeks. It is important to ask your doctor about the best way to do this.

Breaking a tablet

For many medicines it doesn't matter if you break a tablet in two to make it easier to swallow. However for others, this would stop the drug from working properly. For example, some tablets have an outer layer (called an enteric coating) that protects the medicine from being destroyed by stomach acid. Another reason to swallow certain tablets whole is  that they have been designed to release the medicine over a long period of time. This might, for example, lower the risk of side effects - examples include morphine, theophylline and nifedipine (used to lower bloodA fluid that transports oxygen and other substances through the body, made up of blood cells suspended in a liquid. pressure). This type of tablet or capsule is called modified-release (shortened to m/r), sustained-release or slow-release (s/r). If you want to break up tablets, check with your doctor or pharmacist that this will not affect their actions.

Missing a dose

With some medicines it doesn't matter if you miss an occasional dose: if you miss the morning dose of an NSAID, for example, you might get a bit more pain in the evening but otherwise nothing will happen. You won't notice a missed dose of a statinOne of a class of drugs that inhibit cholesterol formation in the liver.. But if you keep missing doses, the medicine will be less effective in the long term. If, for example, you have asthma and you keep missing doses of your inhaled steroid, your asthma control will be worse.

You may want to change the time you take your medicines for religious reasons, such as a festival. Check with your religious leader to be sure you actually need to, and then talk to a health professional about the safest way of doing so.

It can be important to take every dose. If you miss a dose of an oral contraceptiveA term used to describe something that prevents pregnancy., you might get pregnant. If you stop taking an antibiotic before the course has finished, your infectionInvasion by organisms that may be harmful, for example bacteria or parasites. might return. If you miss an insulinA hormone produced by the beta cells of the pancreas that acts to lower blood glucose levels. injection, your bloodA fluid that transports oxygen and other substances through the body, made up of blood cells suspended in a liquid. sugar will go up.

Driving and operating machinery

You will be warned not to drive or operate machinery if you're taking certain medicines. These tend to be medicines that affect behaviour or mood (antidepressants, antipsychotics) or daytime wakefulness (sleeping pills, some antihistamines, opioid analgesicsAnother term for painkillers.) because they make you less alert and interfere with your hand-eye coordination. Many people get used to these effects and, with time, they can resume their activities safely. It's not possible to predict who will be affected or how long the effects will last.

Drinking alcohol

It is safe to drink while taking some medicines and if alcohol is not actually mentioned in the patient information leaflet, there should be no problem. However, with many medicines alcohol should not be taken. Alcohol slows down the brain, and if you have a drink while taking medicines with side effects that affect the brain (such as the ones that can make you sleepy) you'll get a bigger effect and you'll feel even sleepier. If you take a large dose of the medicine and lots of alcohol, you may lose consciousness and could risk your life.

Alcohol also affects the metabolismThe chemical reactions necessary to sustain life. (the body's processing) of some drugs, notably warfarin, and this may change their effects. Conversely, some medicines can interfere with the metabolismThe chemical reactions necessary to sustain life. of alcohol: the most important example is the antibacterial drug metronidazole - take this with alcohol and you're likely to feel sick.

To be sure about the advisability of drinking while taking a course of medicines, you can always ask a health professional such as your doctor or pharmacist.

Pregnancy and breast-feeding

It is important for women who are pregnant or are trying to get pregnant not to take any medicines of any sort - including over-the-counter drugs, traditional and complementary remedies - without first checking with a health professional that it is safe to do so. Your doctor or pharmacist can advise which medicines are safest to take when pregnant or breast-feeding. Although it's difficult to prove that a medicine is perfectly safe for a foetus or breast-feeding infant, some older drugs have not been linked with problems after many years' use.

Children and older people

In general, children and older people (usually those over 65) are more at risk of side effects than other people. This is because they may metabolise and excrete medicines differently from the rest of the population and are more sensitive to the medicines' effects. Usually they need to take a smaller and/or less frequent dose. New medicines for adults are often introduced without being tested for their effects in children and they are not recommended for certain age groups.

Taking other medicines at the same time

Some medicines can safely be taken together, others cannot. A drug interaction occurs when one drug changes the metabolismThe chemical reactions necessary to sustain life. or the effects of another.

For example, the anti-tuberculosis drug rifampicin increases the activity of enzymes in the liverA large abdominal organ that has many important roles including the production of bile and clotting factors, detoxification, and the metabolism of proteins, carbohydrates and fats. that metabolise many other drugs, including oestrogens, corticosteroidsA group of hormones that are produced by the adrenal glands, which sit on top of the kidneys., sulphonylureas and anticoagulants. As a result, these medicines become less effective. Some medicines do the opposite, with equally undesirable side effects: they reduce the activity of liverA large abdominal organ that has many important roles including the production of bile and clotting factors, detoxification, and the metabolism of proteins, carbohydrates and fats. enzymes and so increase the effects of other medicines.

Many people take a medicine they've bought from a pharmacy or complementary therapist while taking another one prescribed by their doctor. Mixing medicines in this way can make them less effective or make side effects worse. For example, the herb St John's Wort reduces the effectiveness of many drugs, including warfarin, several anti-HIV drugs, oral contraceptives and some anti-epileptic drugs.

If you're taking a medicine and you want to start another (of any sort), it's important first to check with the doctor, nurse or pharmacist that it is safe.

When to avoid medicines

Some medical conditions make side effects more likely. These include: some long-term illnesses; allergy or hypersensitivity to a medicine or its ingredients, and reduced liverA large abdominal organ that has many important roles including the production of bile and clotting factors, detoxification, and the metabolism of proteins, carbohydrates and fats. or kidney function (which can reduce the metabolismThe chemical reactions necessary to sustain life. or excretion of many drugs). This might mean that someone should not take a particular medicine at all (called a contraindication) or it might mean that they can do so if the doctor has taken the risk into account and believes it is safe to take the medicine (called a precaution). It is important to tell your doctor if you have any conditions that might need extra caution when taking medicines.

  1. British National Formulary. Link
  2. US National Institutes of Health. Health information. Link
  3. WHO list of essential medicines. Link