In pharmacology, tolerability refers to the degree to which overt
adverse effects
An adverse effect is an undesired harmful effect resulting from a medication or other intervention, such as surgery. An adverse effect may be termed a "side effect", when judged to be secondary to a main or therapeutic effect. The term complic ...
of a drug can be tolerated by a patient.
Tolerability of a particular drug can be discussed in a general sense, or it can be a quantifiable measurement as part of a clinical study. Usually, it is measured by the rate of "dropouts", or patients that forfeit participation in a study due to extreme adverse effects. Tolerability, however, is often relative to the severity of the medical condition a drug is designed to treat.
For instance, cancer patients may tolerate significant pain or discomfort during a chemotherapeutic study with the hope of prolonging survival or finding a cure, whereas patients experiencing a benign condition, such as a headache, are less likely to.
As an example,
tricyclic antidepressant
Tricyclic antidepressants (TCAs) are a class of medications that are used primarily as antidepressants. TCAs were discovered in the early 1950s and were marketed later in the decade. They are named after their chemical structure, which contains ...
s (TCAs) are very poorly tolerated and often produce severe side effects including
sedation
Sedation is the reduction of irritability or agitation by administration of sedative drugs, generally to facilitate a medical procedure or diagnostic procedure. Examples of drugs which can be used for sedation include isoflurane, diethyl ether, ...
,
orthostatic hypotension
Orthostatic hypotension, also known as postural hypotension, is a medical condition wherein a person's blood pressure drops when they are standing up ( orthostasis) or sitting down. Primary orthostatic hypotension is also often referred to as ne ...
, and
anticholinergic
Anticholinergics (anticholinergic agents) are substances that block the action of the acetylcholine (ACh) neurotransmitter at synapses in the central nervous system, central and peripheral nervous system.
These agents inhibit the parasympatheti ...
effects, whereas newer antidepressants have far fewer adverse effects and are well tolerated.
Drug tolerability should not be confused with
drug tolerance
Drug tolerance or drug insensitivity is a pharmacological concept describing subjects' reduced reaction to a drug following its repeated use. Increasing its dosage may re-amplify the drug's effects; however, this may accelerate tolerance, further ...
, which refers to subjects' reduced reaction to a drug following its repeated use.
See also
*
Side effect
In medicine, a side effect is an effect of the use of a medicinal drug or other treatment, usually adverse but sometimes beneficial, that is unintended. Herbal and traditional medicines also have side effects.
A drug or procedure usually use ...
References
Clinical pharmacology
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