Adverse Drug Reactions

Adverse reactions to medications can be broadly classified into allergic(5-10% of reactions) or non-allergic types. Allergic reactions relate to the body’s immune system overreacting to the medication(s) and can be serious or life threatening.

Non-allergic reactions

Overdosage or toxic- too much of the medication is taken or the levels of the drug in the body are too high
Side Effects – undesirable but usually unavoidable effects at the usual dose of medication. For example, dry mouth with anti-histamines. These occur with all medications to some degree but the benefits of treatment usually outweigh the potential side effects. This can be determined by the patient and health care provider.
Drug-drug interactions- medications given together occasionally can increase, decrease or cancel the effects of each other. All medications taken should be discussed with the health care provider and pharmacist.
Intolerance – when reactions to a medication occur below the desirable effective dose or before completion of treatment
Idiosyncratic (or unexpected) – this is an effect of a drug opposite of what would be expected. This response may be inherited, due to age, or due to differences in drug metabolism. For example, Benadryl may make a small child hyperactive and an adult drowsy.

Allergic/Pseudoallergic

An allergic reaction to a drug occurs when a persons’ immune system responds to the intact medication or to one of its components. Allergic drug reactions occur most commonly to antibiotics, anti-inflammatory medications, anti-seizure medications, vaccines, radiographic contrast material, and biological agents such as latex. Symptoms are generally either immediate or occur within 24-48 hours of starting the medication and include rashes, vomiting, diarrhea, difficulty breathing, or swelling of joints, face, or extremities. These reactions require immediate medical attention.