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Toxicity, Medication-Induced Dystonic Reactions
Updated: Sep 30, 2008
Introduction
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. 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. 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.
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%.
Mortality/Morbidity
- In rare instances, airway management may be needed.
- Dystonic reactions typically are 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.
Clinical
History
Dystonic reactions most often occur shortly after initiation of drug treatment; 50% occur within 48 hours and 90% occur within 5 days of initiation of treatment. Risk factors include family history of dystonia, recent history of cocaine or alcohol use, or treatment with a potent dopamine D2 receptor antagonist (eg, fluphenazine, haloperidol).
- Onset of symptoms is sudden, usually within minutes to days of initiating or increasing dose of causative agent.
- Obtain history from others if patient is not able to speak.
- Obtain medication history, including new medications and/or dosage increase.
Physical
- Physical examination findings may include any of the following:
- Oculogyric crisis, deviation of eyes in all directions
- Buccolingual crisis
- Protrusion of tongue
- Trismus
- Forced jaw opening
- Difficulty in speaking
- Facial grimacing
- Torticollis, usually associated with oculogyric and buccolingual crisis
- Opisthotonic crisis
- Lordosis or scoliosis
- Tortipelvic crisis - Typically involves hip, pelvis, and abdominal wall muscles, causes difficulty with ambulation
- Mental status is unaffected.
- Vital signs are usually normal.
- Remaining physical examination findings are normal.
Causes
- Drug-related adverse effects
- Neuroleptics (antipsychotics), antiemetics, and antidepressants are the most common causes of drug-induced dystonic reactions.
- Acute dystonic reactions have been described with every antipsychotic.
- Alcohol and cocaine use increase risk.
- Predisposing factors
- Family history of dystonia
- Viral infections
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References
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Further Reading
Keywords
medication-induced dystonic reactions, dystonic reaction, neuroleptic drug therapy, drug treatment, neuroleptics, neuroleptic agents, dyskinesia, acute dystonic reaction, neuroleptic drugs, involuntary muscle contractions
