An adverse drug reaction (ADR) can be defined as 'an appreciably harmful or unpleasant reaction resulting from an intervention related to the use of a medicinal product; adverse effects usually predict hazard from future administration and warrant prevention, or specific treatment, or alteration of the dosage regimen.

Examples of such adverse drug reactions include rashes, jaundice, anemia, a decrease in the white blood cell count, kidney damage, and nerve injury that may impair vision or hearing. These reactions tend to be more serious but typically occur in a very small number of people.

To many people, adverse events and side effects mean the same thing and are used interchangeably, which is incorrect. Adverse events are unintended pharmacologic effects that occur when a medication is administered correctly while a side effect is a secondary unwanted effect that occurs due to drug therapy.

The ten most common ADRs were constipation, nausea +/- vomiting, fatigue, alopecia, drowsiness, myelosuppression, skin reactions, anorexia, mucositis and diarrhoea. These ADRs have high-documented incidence rates and were also the ten most predictable ADRs in this study.

Adverse reaction. WHO, (1972) A response to a drug which is noxious and unintended, and which occurs at doses normally used in man for the prophylaxis, diagnosis, or therapy of disease, or for the modifications of physiological function.

The majority of ADRs occur as a result of the extension of the desired pharmacologic effects of a drug, often due to the substantial variability in the pharmacokinetics and pharmacodynamics seen among patients. Pharmacological, immunological, and genetic factors are involved in the pathogenesis of ADRs.

Drug rashes can appear as a variety of skin rashes, including pink to red bumps, hives, blisters, red patches, pus-filled bumps (pustules), or sensitivity to sunlight. Drug rashes may involve the entire skin surface, or they may be limited to one or a few body parts. Itching is common in many drug rashes.

Thanks and Regards,

Robert Her.