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Medicines explained

How common classes of medicines work, what they are used for and what to know, in plain English. Brand names are left out on purpose, and AskBioMap does not sell, recommend or promote any medicine.

Talk to your prescriber first

Never start, stop or change a medicine without talking to the doctor who prescribed it. Your pharmacist can answer questions about your medicines. For a possible poisoning or overdose, call the Poisons Information Centre on 13 11 26, or 000 in an emergency.

Pain and inflammation

Paracetamol

Examples
Paracetamol, which is also an ingredient in some other medicines
What it does
Eases mild to moderate pain and lowers a fever. How it works is not fully understood.
Used for
Mild to moderate pain, and fever. It is one of the pain relief medicines used for osteoarthritis.
Possible effects
Side effects are rare.
Good to know
Adults and children aged 12 and over should take no more than 1 gram every 4 to 6 hours, and no more than 4 grams a day. Do not take it with other medicines that contain paracetamol. Liver failure can happen if someone takes too much paracetamol and does not get help, so in a suspected overdose call the Poisons Information Centre on 13 11 26.
On the map

Sources: healthdirect Australia, Paracetamol; healthdirect Australia, Osteoarthritis

Anti-inflammatory painkillers (NSAIDs)

Examples
Ibuprofen, diclofenac and naproxen, and celecoxib, a COX-2 inhibitor
What it does
Reduce pain and inflammation by stopping injured cells from making chemicals called prostaglandins. They do not rely on a steroid.
Used for
Headaches, toothache, period cramps, inflammation, fever and arthritis. They are also used for gout attacks.
Possible effects
High blood pressure is a common side effect. More serious but less common side effects include stomach bleeding and kidney problems, and NSAIDs have been linked to a small increase in the chance of a stroke or heart attack.
Good to know
NSAIDs, including aspirin, can trigger asthma in some people. Do not take them if you have a kidney or liver condition or are pregnant or planning a pregnancy, and do not take two NSAIDs together. Heart problems raise the risk of side effects, and NSAIDs interact with some medicines, including blood thinners.
On the map

Sources: healthdirect Australia, Anti-inflammatory medicines; healthdirect Australia, Gout; healthdirect Australia, Osteoarthritis

Opioid pain relievers

Examples
Oxycodone and other opioid medicines
What it does
Strong pain medicines. Oxycodone, for example, is used only when other pain relief has not worked.
Used for
Severe pain, for example from trauma, surgery, labour or cancer.
Possible effects
Drowsiness, constipation, nausea and vomiting. All opioids can cause life-threatening breathing problems.
Good to know
Dependence can develop even when an opioid is taken exactly as prescribed. Opioids are not suitable with alcohol or other medicines that cause drowsiness, such as benzodiazepines. An overdose can stop someone breathing, and naloxone can temporarily reverse an opioid overdose. Keep opioids out of reach of children and pets, and return unused medicines to any pharmacy.
On the map

Sources: healthdirect Australia, Oxycodone; healthdirect Australia, Constipation

Heart and blood vessels

Low-dose aspirin

Examples
Aspirin
What it does
An antiplatelet blood thinner. Blood thinners help prevent blood clots from forming.
Used for
Blood thinners are prescribed after a stroke or heart attack, for an abnormal heart rhythm, and after some heart procedures.
Possible effects
Heavy bleeding is the most serious possible side effect. Bruising, bleeding gums and nose bleeds can occur.
Good to know
Aspirin can be bought without a prescription, so check the dose with your doctor. Aspirin is a risk factor for gout and is not recommended for gout attacks, and like other NSAIDs it can trigger asthma in some people.
On the map

Sources: healthdirect Australia, Blood thinners; healthdirect Australia, Anti-inflammatory medicines; healthdirect Australia, Gout

Statins

Examples
Atorvastatin, fluvastatin, pravastatin, rosuvastatin, simvastatin
What it does
Lower the level of LDL ("bad") cholesterol.
Used for
High cholesterol, which raises the risk of heart disease and stroke. Statins can help even people without diagnosed heart disease, and for people at high risk they lower that risk by around 20% on average.
Possible effects
Muscle symptoms occur in only about 5% more people taking statins than people taking a placebo. More serious muscle inflammation or muscle breakdown occurs very rarely.
Good to know
Talk to your doctor about any muscle pain or weakness, and do not stop a statin unless your doctor advises it. Research does not support the idea that CoQ10 supplements reduce muscle pain caused by statins, according to NCCIH.
On the map

Sources: NPS MedicineWise, Statin medicines: frequently asked questions; healthdirect Australia, Cholesterol; NIH NCCIH, Coenzyme Q10

ACE inhibitors and ARBs (sartans)

Examples
ACE inhibitors, whose names often end in pril, and ARBs, whose names often end in sartan
What it does
Lower blood pressure by widening blood vessels.
Used for
High blood pressure. Both are also used to treat heart failure.
Possible effects
ACE inhibitors can cause a dry cough, tiredness, high potassium, kidney problems, headache, dizziness and nausea. ARBs can cause dizziness, headache and high potassium.
On the map

Sources: healthdirect Australia, Blood pressure medicines; Heart Foundation, What is heart failure?

Beta blockers

Examples
Atenolol, bisoprolol, carvedilol, metoprolol, propranolol, sotalol
What it does
Make the heart beat more slowly and lower blood pressure by blocking the effects of the hormone adrenaline. They also relax blood vessels.
Used for
High blood pressure, angina, coronary heart disease, heart failure, abnormal heart rhythms, migraine, anxiety with a fast heart rate, and some tremors.
Possible effects
Dizziness, light-headedness or a slow heartbeat. See your doctor straight away if these happen.
Good to know
Do not stop taking beta blockers suddenly. They should be avoided or used with caution in people with asthma, and people with diabetes may need to check their blood sugar more often.
On the map

Source: healthdirect Australia, Beta blockers

Diuretics (fluid tablets)

Examples
Hydrochlorothiazide and indapamide (thiazide types), furosemide, also called frusemide (a loop diuretic), and spironolactone (potassium-sparing)
What it does
Make the kidneys produce more urine and release more electrolytes into it, removing excess water.
Used for
High blood pressure, and fluid retention due to heart failure, liver cirrhosis or kidney problems.
Possible effects
Dizziness, weakness, muscle cramps, thirst and needing to urinate more often. Some cause low potassium and others high potassium, and they can affect sodium, calcium, magnesium and uric acid. Some can cause gout.
Good to know
Take them early in the day to avoid passing urine at night. Your doctor will arrange blood tests to check kidney function and electrolytes, and should see you within 2 weeks of starting or changing the dose. Seek medical help immediately if you faint or feel very dizzy, confused or weak.
On the map

Sources: healthdirect Australia, Diuretic medicines; healthdirect Australia, Blood pressure medicines

Anticoagulants (blood thinners)

Examples
Warfarin, apixaban, dabigatran, rivaroxaban
What it does
Help prevent blood clots from forming.
Used for
Treating blood clots, and lowering the chance of clots and stroke after a heart attack or stroke, with an abnormal heart rhythm such as atrial fibrillation, or after some heart procedures.
Possible effects
Heavy bleeding is the most serious possible side effect. Bruising, bleeding gums and nose bleeds can occur.
Good to know
See a doctor straight away or go to an emergency department if you cough up blood, have black vomit or black stools, or bleeding that does not stop. Warfarin needs regular blood tests, and it helps to eat the same types of food regularly, especially foods high in vitamin K such as green leafy vegetables. Blood thinners interact with many medicines, vitamins and herbal medicines, and high doses of omega-3 supplements may cause bleeding problems with warfarin.
On the map

Sources: healthdirect Australia, Blood thinners; healthdirect Australia, Atrial fibrillation; NIH Office of Dietary Supplements, Omega-3 fatty acids fact sheet for consumers

Diabetes and metabolism

Metformin

Examples
Metformin
What it does
Makes the body more sensitive to insulin.
Used for
Type 2 diabetes.
Possible effects
The most common side effects mainly affect the stomach and bowel.
Good to know
Long-term metformin use is a risk factor for low vitamin B12, according to Pathology Tests Explained. Always speak to your doctor or diabetes nurse practitioner before reducing or stopping any diabetes medicine.
On the map

Sources: National Diabetes Services Scheme (NDSS), Medicines for diabetes fact sheet; Pathology Tests Explained, Vitamin B12 and folate

SGLT2 inhibitors

Examples
Dapagliflozin, empagliflozin
What it does
Lower blood glucose by removing extra glucose from the body through the urine.
Used for
Type 2 diabetes. They also help protect heart and kidney health, and are one of the medicine groups used for heart failure.
Possible effects
Urinary tract infections and genital thrush.
Good to know
Diabetic ketoacidosis (DKA) is a rare but serious side effect.
On the map

Sources: National Diabetes Services Scheme (NDSS), Medicines for diabetes fact sheet; Heart Foundation, What is heart failure?

Insulin

Examples
Insulin given by injection, pen or pump
What it does
Replaces insulin, the hormone that controls the amount of glucose in the blood.
Used for
All people with type 1 diabetes, and some people with type 2 diabetes.
Possible effects
Hypoglycaemia (low blood sugar) is a common and sometimes serious complication of insulin therapy.
Good to know
Drinking alcohol with insulin can increase the risk of a hypo. Diabetic ketoacidosis (DKA) is a medical emergency, and missing insulin injections is one risk. If someone has signs of DKA or becomes confused or unconscious, call triple zero (000) for an ambulance.
On the map

Sources: National Diabetes Services Scheme (NDSS), Medicines for diabetes fact sheet; healthdirect Australia, Type 1 diabetes; healthdirect Australia, Type 2 diabetes

Hormones

Thyroid hormone (levothyroxine)

Examples
Levothyroxine (thyroxine)
What it does
A synthetic version of the thyroid hormone thyroxine (T4).
Used for
Hypothyroidism (an underactive thyroid), including when it is caused by Hashimoto's disease.
Good to know
In most cases it is taken for the rest of your life, and blood tests check hormone levels so the dose can be adjusted. Biotin supplements can affect thyroid blood tests, so Pathology Tests Explained advises not taking biotin for two days before the test.
On the map

Sources: healthdirect Australia, Hypothyroidism (underactive thyroid); healthdirect Australia, Hashimoto's disease; Pathology Tests Explained, Thyroid function tests

Corticosteroids (steroid medicines)

Examples
Prednisolone tablets, and steroid creams, inhalers, nasal sprays and injections
What it does
Man-made versions of cortisol, a hormone made by the adrenal glands. They reduce inflammation.
Used for
Inflammatory diseases such as asthma, ulcerative colitis, lupus and some forms of arthritis, including rheumatoid arthritis; skin conditions such as dermatitis and eczema; hay fever (as nasal sprays); and managing Addison's disease.
Possible effects
Side effects listed by the Better Health Channel include thin skin, bruising, high blood pressure, infections, fluid retention, diabetes and thinning of the bones (osteoporosis). High doses taken by mouth can cause the features of Cushing's syndrome, and corticosteroids are a risk factor for loss of muscle mass.
Good to know
Suddenly stopping the medication can be dangerous. After long-term, high-dose use, the body may not make enough cortisol of its own for a time.
On the map

Sources: Better Health Channel (Victorian Government), Hormones: cortisol and corticosteroids; healthdirect Australia, Cushing's syndrome; healthdirect Australia, Osteoporosis; healthdirect Australia, Loss of muscle mass; Better Health Channel (Victorian Government), Rheumatoid arthritis; healthdirect Australia, Eczema; healthdirect Australia, Hay fever

Combined oral contraceptive pill

Examples
Pills containing oestrogen and progestogen
What it does
Prevents pregnancy, mainly by stopping the ovaries from releasing an egg each month.
Used for
Contraception. It can also be used to regulate periods, reduce period pain or improve acne.
Possible effects
Nausea, sore or tender breasts, headaches and irregular vaginal bleeding. It causes a very small increase in the risk of deep vein thrombosis (a blood clot), heart attack or stroke, and it is one possible cause of fluid retention.
Good to know
It is more than 99% effective when used correctly, and about 93% effective allowing for mistakes. It is not suitable for people over 35 who smoke, or for people with certain types of migraine. Vomiting within 3 hours of a pill, very severe diarrhoea, and some medications or natural remedies can make it less effective.
On the map

Sources: Better Health Channel (Victorian Government), Contraception: the combined pill; healthdirect Australia, Fluid retention

Lungs

Asthma inhalers (relievers and preventers)

Examples
Reliever puffers, and preventer inhalers that contain an inhaled corticosteroid
What it does
Relievers relax the muscles around the airways and start to work within minutes. Preventers make the airways less sensitive to triggers and reduce redness and swelling.
Used for
Asthma. Inhaled medicines are also used to treat COPD.
Possible effects
Relievers can cause a faster heart rate and shaking hands. Preventers can cause a hoarse voice and mouth thrush.
Good to know
Gargle, rinse and spit after using a preventer. Take a preventer every day as directed, even when you feel well. It can take two to four weeks to reach its full effect. Needing your reliever more than two days a week may mean your asthma is not well controlled, so see your doctor.
On the map

Sources: Better Health Channel (Victorian Government), Asthma; Asthma Australia, Relievers; Asthma Australia, Preventers; healthdirect Australia, Chronic obstructive pulmonary disease (COPD)

Digestion

Proton pump inhibitors (PPIs)

Examples
Esomeprazole, lansoprazole, omeprazole, pantoprazole, rabeprazole
What it does
Control stomach acid by reducing the amount of acid in the stomach.
Used for
Heartburn and reflux, and gastritis.
Possible effects
Headache, nausea, vomiting, diarrhoea, tummy pain, constipation and wind.
Good to know
They work best taken about 30 to 60 minutes before a meal. Taking them for longer than recommended for heartburn, usually more than 8 weeks, can increase the risk of side effects, so ask your doctor about the lowest dose that controls your symptoms. Long-term use is a risk factor for low vitamin B12, according to Pathology Tests Explained.
On the map

Sources: healthdirect Australia, Heartburn; healthdirect Australia, Gastritis medicines; Pathology Tests Explained, Vitamin B12 and folate

Mental health

SSRI antidepressants

Examples
Citalopram, sertraline
What it does
Antidepressants are thought to work by affecting the levels of several brain chemicals (neurotransmitters), including serotonin, though this is not fully understood. SSRIs are the most commonly prescribed antidepressant class in Australia.
Used for
Depression and anxiety.
Possible effects
Headaches, dizziness, nausea, weight gain, restlessness, sleep difficulties and sexual problems.
Good to know
Depression can start to improve in 2 to 4 weeks, with the full effect in 6 to 8 weeks. Stopping suddenly is likely to cause withdrawal symptoms, so reduce the dose with your doctor. A rare side effect is serotonin toxicity, which is more likely when an antidepressant is combined with other antidepressants or some other medicines, and St John's wort can cause serious serotonin-related side effects with some antidepressants. Some young people may have more thoughts of self-harm or suicide when starting an antidepressant, according to healthdirect.
On the map

Sources: healthdirect Australia, Antidepressants; healthdirect Australia, Medicines for anxiety; NIH NCCIH, St. John's wort

SNRI antidepressants

Examples
Duloxetine, venlafaxine
What it does
Antidepressants that act on serotonin and noradrenaline, two brain chemicals.
Used for
Depression, including more severe or persistent depression, anxiety, and nerve pain.
Possible effects
Nausea, weight gain, headaches, dizziness, anxiety or agitation, sweating, dry mouth and sexual problems.
Good to know
Antidepressants take several weeks to work. Stopping suddenly is likely to cause withdrawal symptoms, so reduce the dose with your doctor.
On the map

Sources: healthdirect Australia, Antidepressants; healthdirect Australia, Medicines for anxiety; healthdirect Australia, Nerve pain medication

Benzodiazepines

Examples
Diazepam, lorazepam
What it does
Increase the calming effect of certain chemicals in the brain.
Used for
Anxiety, for only a short time (2 to 4 weeks).
Possible effects
Excessive drowsiness, light-headedness, increased saliva, slurred speech and changes in vision.
Good to know
Benzodiazepines are addictive, and people can become dependent on them. Do not mix them with alcohol or other drugs, including opioids, and do not drive if you are affected.
On the map

Sources: healthdirect Australia, Medicines for anxiety; healthdirect Australia, Oxycodone

Antipsychotics

Examples
Aripiprazole, asenapine, haloperidol, olanzapine, quetiapine, risperidone
What it does
Treat symptoms such as hallucinations, delusions and extreme agitation.
Used for
Bipolar disorder. Quetiapine is also one of the medicines used for anxiety.
Possible effects
Weight gain, type 2 diabetes or increased cholesterol, drowsiness, dry mouth, sexual problems, constipation and blurred vision.
On the map

Sources: healthdirect Australia, Medicines for bipolar disorder; healthdirect Australia, Medicines for anxiety

Lithium and other mood stabilisers

Examples
Lithium, sodium valproate, carbamazepine, lamotrigine
What it does
Mood stabilisers treat or prevent mania by reducing mood swings.
Used for
Bipolar disorder, where lithium is commonly used as a long-term treatment. Lithium is also used for mania, hypomania, schizophrenia and some depression.
Possible effects
Too much lithium can harm the thyroid, kidneys and central nervous system, and long-term use can cause thyroid and kidney problems.
Good to know
Lithium needs regular blood tests to check the level is not too low or too high, plus kidney and thyroid tests. Dehydration from fever, vomiting or diarrhoea can cause lithium toxicity, and NSAIDs and some blood pressure medicines raise the risk. Drink plenty of fluids in hot weather and when exercising, and do not follow a low-salt diet. See a doctor straight away for signs of toxicity such as muscle weakness, shaking, slurred speech, confusion or severe drowsiness.
On the map

Sources: healthdirect Australia, Lithium; healthdirect Australia, Medicines for bipolar disorder; healthdirect Australia, Hypothyroidism (underactive thyroid)

ADHD stimulant medicines

Examples
Dexamfetamine, methylphenidate
What it does
Help to focus attention, shut out distraction and improve concentration.
Used for
Mainly attention deficit hyperactivity disorder (ADHD).
Possible effects
Loss of appetite, nervousness and trouble sleeping.
Good to know
Taking them with meals helps avoid stomach upsets. Report chest pain, a severe or persistent headache, a fast heartbeat or new or worsening aggression to the doctor. Do not stop them without checking with the doctor, and never give them to anyone else.
On the map

Source: Perth Children's Hospital (Child and Adolescent Health Service, WA), Dexamfetamine (dexamphetamine) or methylphenidate

Allergy and immunity

Antihistamines

Examples
Less sedating types such as bilastine, cetirizine, desloratadine, fexofenadine and loratadine; sedating types such as dexchlorpheniramine, diphenhydramine, doxylamine and promethazine
What it does
Block the action of histamine, a chemical released in allergic reactions.
Used for
Allergies and allergic reactions such as hay fever, hives and insect bites or stings. Sedating types are also used for itch, nausea and vomiting. A doctor may recommend an antihistamine when eczema itch disturbs sleep.
Possible effects
Drowsiness and dry mouth. Of the less sedating types, cetirizine is the most likely to cause sleepiness.
Good to know
Sedating antihistamines are not recommended for treating allergic reactions and should not be given to children under 2. They may increase the chance of dementia, especially in people over 65. Take care with driving.
On the map

Sources: healthdirect Australia, Antihistamines; healthdirect Australia, Hay fever; healthdirect Australia, Eczema

Antibiotics

Examples
Amoxicillin (broad-spectrum), penicillin (narrow-spectrum), and many others
What it does
Treat infections caused by bacteria. They do not work against viruses, which cause most colds, flu and COVID-19.
Used for
Bacterial infections.
Possible effects
Diarrhoea, nausea and vomiting, thrush in the mouth or vagina, and allergic reactions, most often affecting the skin.
Good to know
Take them for as long as you are told. The main cause of antibiotic resistance is antibiotic use. There is some evidence that taking probiotics during a course can reduce antibiotic-associated diarrhoea, and antibiotics can greatly reduce gut microbe populations, according to the Australian Academy of Science.
On the map

Sources: healthdirect Australia, Antibiotics; Australian Academy of Science, Gut bacteria: the inside story

Bones and joints

Bisphosphonates

What it does
Slow down the natural loss of bone density.
Used for
Osteoporosis.
Good to know
Bisphosphonates are one of several medicines for osteoporosis. Others include denosumab, romosozumab, raloxifene, menopausal hormone treatment and teriparatide. Exercises such as walking and strength training can also improve bone density, and preventing falls is part of managing osteoporosis.
On the map

Source: healthdirect Australia, Osteoporosis

Disease-modifying anti-rheumatic drugs (DMARDs)

Examples
Methotrexate, and more targeted medicines called biologics
What it does
Treat rheumatoid arthritis. Early treatment helps control the inflammation.
Used for
Rheumatoid arthritis.
Good to know
Early diagnosis matters so treatment can start quickly. NSAIDs interact with methotrexate, according to healthdirect.
On the map

Sources: Better Health Channel (Victorian Government), Rheumatoid arthritis; healthdirect Australia, Anti-inflammatory medicines

Brain and nerves

Gabapentinoids

Examples
Gabapentin, pregabalin
What it does
Anti-seizure medicines that are also used for nerve pain. Most nerve pain medicines work by calming down nerve activity.
Used for
Nerve pain. Pregabalin is also one of the medicines used for anxiety.
Possible effects
Drowsiness, weight gain, dry mouth, blurred vision and swelling (oedema).
Good to know
It is best to avoid or limit alcohol while taking medicines for nerve pain. Do not stop or change your medicines without talking to your doctor.
On the map

Sources: healthdirect Australia, Nerve pain medication; healthdirect Australia, Medicines for anxiety

General education only. For information about a specific medicine, see the consumer medicine information, ask your pharmacist, or search healthdirect medicines information.

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