Toxicity, Medication-Induced Dystonic Reactions
- Author: Geofrey Nochimson, MD; Chief Editor: Asim Tarabar, MD more...
Background
Dystonic reactions are adverse extrapyramidal effects that often occur shortly after the initiation of neuroleptic drug therapy. These reactions may occur with a wide variety of medications. Dystonic reactions (ie, dyskinesias) are characterized by intermittent spasmodic or sustained involuntary contractions of muscles in the face, neck, trunk, pelvis, and extremities.[1] Dystonic reactions are rarely life threatening, yet are very uncomfortable and often produce significant anxiety and distress for patients. Fortunately, treatment is extremely effective, and motor disturbances resolve within minutes.
Pathophysiology
Although dystonic reactions are occasionally dose related, these reactions are more often idiosyncratic and not predictable. They appear to result from drug-induced alteration of dopaminergic-cholinergic balance in the nigrostriatum (ie, basal ganglia). Most drugs produce dystonic reactions by nigrostriatal dopamine D2 receptor blockade, which leads to an excess of striatal cholinergic output. High-potency D2 receptor antagonists are most likely to produce an acute dystonic reaction.[2] Agents that balance dopamine blockade with muscarinic M1 receptor blockade are less likely to produce a dystonic reaction. Paradoxically, an alternative cause of dystonic reactions may be increased nigrostriatal dopaminergic activity that occurs as a compensatory response to dopamine receptor blockade.
Epidemiology
Frequency
United States
Incidence of acute dystonic reactions varies according to individual susceptibility, drug identity, dose, and duration of therapy. For patients on neuroleptics, the overall incidence of dystonic reactions is approximately 2%.[3]
Mortality/Morbidity
In rare instances, airway management may be needed.
Dystonic reactions are typically not life threatening and result in no long-term effects.
Sex
Incidence of dystonic reactions is greater in males than in females.
Age
These reactions are most common in children, teens, and young adults (ie, 5-45 years).
The risk of reaction decreases as age increases.
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