Some people who take statins experience muscle pain and/or weakness, which tends to affect the large muscle groups such as the calves, thighs, buttocks and upper arms and to be symmetrical in nature. This is most likely to occur in the first three months of treatment. A blood test for creatinine kinase (CK) can be used to assess muscle damage. Other adverse effects or cautions include:

• Hepatic toxicity: It is recommended that liver function tests (transaminases) are checked at baseline, three months and 12 months. Statins are contraindicated in active liver disease or if there are unexplained persistent elevations of the transaminase levels
• New onset diabetes: Some people who take a statin are at greater risk of diabetes, regardless of whether they take a statin or not. It is generally considered that the risk of statin-induced diabetes is low and outweighed by the potential benefits on CV risk. Lifestyle modification should be reinforced
• Common side effects: These affect up one in 10 statin users and include allergic reactions, headache, nausea, constipation, wind, indigestion, diarrhoea, inflammation of the nasal passages, pain in the throat or nose bleeds. If symptoms appear to be statin-related for non-allergic reactions, stopping the statin and re-challenging when symptoms have resolved, with an alternative statin or reduced dosage if preferred, can be a successful strategy
• Contraindications: Statins are contraindicated in pregnancy and breastfeeding.

Drug interactions

There are a number of significant drug interactions with statins that may affect the choice of statin or limit the maximum dosage that can be prescribed. In 2014, the MHRA produced an updated alert highlighting statin interactions, but this list is not exhaustive and up-to-date information should also be consulted.

Grapefruit and/or grapefruit juice should also be avoided when taking simvastatin and limited to no more than one small glass of juice per day in patients taking atorvastatin. There is no interaction between rosuvastatin, pravastatin or fluvastatin and grapefruit.

Interactions with herbal and OTC medicines should also be taken into consideration.