Multiple medications and drug interactions

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Key points

  • The more drugs you take, the greater the risk of drug interactions and side-effects.
  • It’s important to tell your doctors and pharmacists about all the other medicines you take.
  • An annual medication review is an opportunity to check that your medicines are right for you.

Many people with HIV need to take several other medicines to treat other health conditions. This may be necessary for your health, but taking multiple medications (sometimes called ‘polypharmacy’) can occasionally cause problems.

The more drugs you take, the greater the risk of experiencing drug interactions and side-effects. A drug interaction is when one medicine affects how another medicine works. For example, taken together, one medicine may increase the side-effects of another medicine.

If you have lots of medication to take, it can become harder to keep track of when to take each one. You may be less motivated to keep up your adherence to all your medication.

Also, sometimes, people end up taking medicines which they no longer need. This is more likely to happen if you see several doctors.

Practical advice

It is important that anyone prescribing or dispensing medication knows about all other medicines and drugs that you are taking – this includes those prescribed by another doctor; over-the-counter medicines (including inhalers and nasal sprays); supplements, herbal and alternative treatments; and recreational drugs.

One way you can do this is to have a list of all the medicines and drugs you take – note down the name of each drug and what you take it for. Bring the list with you whenever you see a doctor or pharmacist.

Alternatively, there are also smartphone apps and booklets you can use to keep a record of your medications. Some of these can also help remind you of when you need to take your pills too. Another way you can show the pharmacist everything you take is to have photos of the medicine packages on your phone.

It’s best to always go to the same high-street chemist (community pharmacy). This will mean that your prescription records are in the same place, allowing the pharmacist to check for potential drug interactions.

If possible, tell the pharmacist about the anti-HIV drugs you are taking. Community pharmacies often have a private area for consultations, or you could write the name of the drugs down and hand them to him or her. If you do need to mention the name of your anti-HIV drugs, it’s very unlikely that anyone around you will recognise what they are used to treat.

It's very helpful to have an annual medication review. This could be done by the pharmacist at your HIV clinic, your community pharmacist, or one of your doctors. The National Institute for Health and Care Excellence (NICE) recommends that people with long-term conditions and people taking multiple medications have regular reviews.


drug interaction

A risky combination of drugs, when drug A interferes with the functioning of drug B. Blood levels of the drug may be lowered or raised, potentially interfering with effectiveness or making side-effects worse. Also known as a drug-drug interaction.


An essential organ involved in digestion of food and excretion of waste products from the body.


The act of taking a treatment exactly as prescribed. This involves not missing doses, taking doses at the right time, taking the correct amount, and following any instructions about food.


A feeling of unease, such as worry or fear, which can be mild or severe. Anxiety disorders are conditions in which anxiety dominates a person’s life or is experienced in particular situations.


A mental health problem causing long-lasting low mood that interferes with everyday life.

When you have the review, put everything you take (prescribed medicines; over-the-counter medicines; supplements, herbal and alternative treatments) in a bag and bring it with you. Make sure you mention any alcohol, recreational or street drugs you take as well as these can also interact with your medication. Discuss any symptoms or side-effects that you have been experiencing.

After a medication review, the pharmacist or doctor may recommend some changes, such as stopping a medicine that you no longer need, switching a medicine to a newer or better version, or reducing the number of times a day you need to take medicines. The review may show that there is a medicine which you need but have not been getting.

Especially if you are taking a large number of medicines at different times of the day, a pill box with compartments for the days of the week and times of the day may be useful. It may help you keep track of what you need to take, when. Your pharmacist can give you advice on other ways to help you maintain your adherence. 

The University of Liverpool provides an online tool to check for interactions between anti-HIV drugs, other medications and recreational drugs. You enter the names of the medication you are taking and the results are provided with a traffic-light system: if the result is red or amber, it’s worth checking with your doctor or pharmacist. If it’s green, there shouldn’t be any problem. Visit or download the Liverpool HIV iChart app for iPhone or android.

More information about drug interactions and side-effects

Some drug combinations are contraindicated – which means you definitely should not take them together. Reasons for this include serious side-effects, or interactions which make one or both drugs ineffective or toxic. 

Other interactions are less dangerous, but still need to be reviewed by a healthcare professional. Levels of one or both drugs in your blood may be affected and you may need to change the doses you take. 

Interactions are possible between anti-HIV drugs and a wide range of other medication. Some anti-HIV drugs can interact with antihistamines, asthma inhalers or nasal sprays (which contain steroids) and treatments for indigestion that are bought over the counter. Interactions may occur with drugs used to manage heart health (including drugs to keep cholesterol or blood pressure under control, or to help prevent heart failure); medication for depression and anxiety; and drugs used to manage pain.

"It is important that anyone prescribing or dispensing medication knows about all other medicines and drugs that you are taking."

Anti-HIV drugs can also interact with recreational drugs. Some herbal and alternative treatments (such as St John’s Wort and echinacea) can lower levels of some anti-HIV drugs.

Some combinations of medicines are especially problematic. If you are taking several different medicines that can affect your brain and nervous system, you are much more likely to experience drowsiness, confusion or memory problems. This can lead to falls and accidents.

Another factor that can have an impact is age. As we get older, our bodies change and process medicines differently. The liver and kidneys may work more slowly, affecting the way a drug breaks down and is removed from the body. As a result of weight loss, decreased body fluid or increased fatty tissue, medicines and drugs may stay in the body longer and cause more severe side-effects. For these reasons, your doctors may change some of your drugs to medicines which put less strain on your liver and kidneys, or lower the dose you take.

Next review date

Thanks to Heather Leake Date, Chris Sandford and Sonali Sonecha for their advice.