Approach to medication-induced movement disorders: Clinical sciences

Medication-induced movement disorders are a group of conditions characterized by abnormal movements resulting from exposure to certain medications. These medications often include serotonergic medications, dopamine antagonists, and anticonvulsants, which are all commonly prescribed in psychiatric treatment.

Medication-induced movement disorders can range from mild to severe and from acute to chronic. Life-threatening ones requiring emergency intervention include serotonin syndrome and neuroleptic malignant syndrome. Less severe ones include acute dystonia, postural tremor, extrapyramidal symptoms, akathisia, and tardive dyskinesia.

If a patient presents with a chief concern suggesting a medication-induced movement disorder, first, perform an ABCDE assessment to determine if they are stable or unstable. If unstable, stabilize their airway, breathing, and circulation, which may require supplemental oxygen and even endotracheal intubation. Next, obtain IV access, and consider starting IV fluids. Finally, begin continuous vital sign monitoring, including respiratory rate, pulse oximetry, and cardiac telemetry.

Once you have initiated the acute management, your next step is to obtain a focused history and physical exam, and order labs, including a CPK or creatine phosphokinase, CBC, and CMP. In unstable patients, you should think about serotonin syndrome or neuroleptic malignant syndrome.

Patients with serotonin syndrome typically report recent exposure to one or more serotonergic medications, such as serotonin reuptake inhibitors, tricyclic antidepressants, or monoamine oxidase inhibitors. Additionally, there might be exposure to synthetic opioid tramadol, the muscle relaxer cyclobenzaprine, and the antibiotic linezolid, all of which have serotonergic properties as well.

As for the physical exam, look out for elevated temperature, hypertension, tachycardia, muscle rigidity, tremor or myoclonus, hyperreflexia, diaphoresis, and even confusion and seizures in severe cases. If you see these findings, think of serotonin syndrome.

Here is a clinical pearl! The most important step in the acute management of serotonin syndrome is to discontinue the serotonergic medications immediately, followed by supportive care. Additionally, consider adding anticonvulsants if seizures are present.

Okay, let’s move on to neuroleptic malignant syndrome, which is a rare but life-threatening condition commonly associated with the use of first-generation antipsychotics. It typically arises within the first four weeks of treatment or during dose adjustments.

History usually reveals exposure to one or more antipsychotic medications. On physical exam, you may notice generalized muscle rigidity, hyperthermia with diaphoresis, and altered mental status. Additionally, your patient might have low or high blood pressure and tachycardia.

When it comes to labs, CPK is usually greater than 10 times the upper normal limit. You might also find elevated white cell count, liver enzymes, and creatinine. With these findings, you can diagnose neuroleptic malignant syndrome.

Here’s another clinical pearl! Acute treatment of neuroleptic malignant syndrome focuses on discontinuing the antipsychotic and providing supportive care. Additionally, you may consider medications like a dopamine agonist such as bromocriptine; a muscle relaxant like dantrolene; and benzodiazepines if your patient has agitation. In severe, treatment-resistant cases, electroconvulsive therapy might be necessary.

Alright, now let’s go back to the ABCDE assessment and take a look at stable patients. As before, obtain a focused history and physical exam. Patients usually report recently starting a new psychiatric medication; or increasing the dose of a psychiatric medication. They might also report abnormal movements, such as tremors, or the feeling of restlessness.

The physical exam can reveal a variety of abnormal movements depending on the underlying disorder. These include chorea, characterized by brief, involuntary, and random, irregular contractions; myoclonus, which is a brief, involuntary, shock-like jerk; or dystonia, presenting as a sudden onset of sustained contraction in a muscle or muscle group. If you see these findings, consider a medication-induced movement disorder.

Now, a type of abnormal movement present during a physical exam can help determine which movement disorder you are dealing with. Let’s start by assessing for dystonia.

Logically, if your patient has dystonia, consider acute dystonia as the diagnosis. In this case, patients may report recent use of antipsychotics, accompanied by an abrupt onset of muscle contractions. First-generation antipsychotics are associated with most cases of acute dystonia compared to second-generation ones. Among patients treated with first-generation antipsychotics, approximately 10 percent will develop acute dystonia, while only 2 percent treated with second-generation antipsychotics are affected.