<unk> s may be classified by e.g. cause and severity. Cause *Type A: Augmented pharmacologic effects - dose dependent and predictable :Type A reactions, which constitute approximately 80% of<unk> s, are usually a consequence of the drug’s primary pharmacological effect (e.g. bleeding when using the anticoagulant warfarin) or a low therapeutic index of the drug (e.g. nausea from digoxin), and they are therefore predictable. They are dose-related and usually mild, although they may be serious or even fatal (e.g. intracranial bleeding from warfarin). Such reactions are usually due to inappropriate dosage, especially when drug elimination is impaired. The term ‘side effects’ is often applied to minor type A reactions. * Type B: Idiosyncratic Types A and B were proposed in the 1970s, and the other types were proposed subsequently when the first two proved insufficient to classify<unk> s. Seriousness The U.S Food and Drug Administration defines a serious<unk>  event as one when the patient outcome is one of the following: * Death * Life-threatening * Hospitalization (initial or prolonged) * Disability - significant, persistent, or permanent change, impairment, damage or disruption in the patient's body function/structure, physical activities or quality of life. * Congenital abnormality * Requires intervention to prevent permanent impairment or damage Severity is a point on an arbitrary scale of intensity of the<unk>  event in question. The terms "severe" and "serious", when applied to<unk>  events, are technically very different. They are easily confused but can not be used interchangeably, requiring care in usage. A headache is severe if it causes intense pain. There are scales like "visual analog scale" that help clinicians assess the severity. On the other hand, a headache is not usually serious (but may be in case of subarachnoid haemorrhage, subdural bleed, even a migraine may temporally fit criteria), unless it also satisfies the criteria for seriousness listed above.
Adverse drug reaction
Bullous drug reaction
Anticonvulsant hypersensitivity syndrome
Idiosyncratic drug reaction
Drug interaction
Foreign body reaction
Drug intolerance
Paraneoplastic syndrome