ADRs

Introduction to ADRs

Adverse drug reactions (ADRs), also known as ‘side effects’, ‘adverse
drug events’, or ‘drug misadventures’, are a frequent cause of morbidity in hospital and the community. They have a significant cost both financially and in terms of quality of life. 
Few studies of ADRs have been carried out in the community so the effect on primary care is harder to assess, but studies in the hospital environment have shown the following.

• ADRs occur in 10–20 % of patients in hospital.
• ADRs are responsible for 5 % of admissions to hospital.
• ADRs might be responsible for 1 in 1000 deaths in medical wards.
• ADRs are the most common cause of iatrogenic injury in hospital
patients.

The World Health Organization (WHO) defines an ADR as follows:
‘ a drug-related event that is noxious and unintended and occurs at doses used in
humans for prophylaxis, diagnosis or therapy of disease or for the modification
of physiological function .’

However, this definition does not take into account the following
scenarios, all of which can also cause ADRs:
• overdose (including prescribing or administration errors)
• therapeutic failure
• drug interactions
• drug withdrawal.

Pharmacists have an important role in identifying, reporting, and preventing
ADRs.