Consider this: the prescription your doctor wrote for you may not be "officially" approved for your illness. Before you panic, this may not be as alarming as you think.

In the United States, President Trump recently signed a bill which brought to the top of the agenda the concept of using medicines outside their officially permitted purpose.

In the United Kingdom, a medicine's terms of use are defined by the marketing authorisation or product licence granted by the Medicines and Healthcare products Regulatory Agency (MHRA). This contains a summary of product characteristics which outlines the conditions it is intended to treat, recommended doses, warnings and side effects. It gives the comfort that the risks of the medicine have been assessed by the regulator and considered to be offset by the benefits.

However, "off-label" medicine is not as concerning as it may sound. It can include drugs used for one disease but found to be beneficial for sufferers of another, drugs given in a different way – if the drug is approved in capsule form but given in an oral solution, or drugs given at a different dose to the approved amount.

Off-label use of medicines can be beneficial. Take propranolol as an example – this drug has been approved for treatment of hypertension and the prevention of angina pectoris. However, a study in 1991 found that taking propranolol prior to an exam improved the performance of students prone to cognitive dysfunction from test anxiety. Propranolol has also been shown to assist with sports, public speaking and musical performances. Even household aspirin has off-label beneficial properties.

In 2006, a study found that in a sample of common medicines, 21% of prescriptions were for off-label use. Such practice is more common within certain subgroups of patients; in paediatrics especially there are difficulties in developing age-appropriate formulations – 78% of children discharged were taking an off-label medicine. There are clinical situations where it may be in the best interests of the patient to use a medicine off-label. It can even become the predominant treatment for an illness. For example in the US, the FDA has not approved the use of tricyclic antidepressants to treat neuropathic pain, yet that is considered to be standard treatment.

A greater responsibility is placed on healthcare professionals when they prescribe off-label medicine. They must be satisfied that this approach would best serve the needs of the patient, and pay close attention in particular to the risks associated with the off-label use of that medicine such as adverse reactions. To this end, healthcare professionals would be wise to ensure that they use consent forms which highlight that the medicine is being prescribed off-label, even if such use is commonplace.

To any anxious readers, you can comfort yourself with the knowledge that off-label use of medicines is a well-established aspect of our healthcare system. Generally, doctors are not irresponsibly throwing any and every drug in the book at a disease, they are carefully considering known beneficial results.