In a series of patients reported by Miller and colleagues,5 131 who had a drug-induced movement disorder continued on the offending medication for, on average, 6 months after onset of symptoms. In a study by Esper and coworkers of DIP patients at movement disorder clinics, average time to correct diagnosis after symptoms were reported was 1.8 years.1
Our patient exhibited symptoms for 1 month before the correct diagnosis was made, at her third visit for those symptoms.
CASE: Resolved
The patient was hospitalized and the anti-emetics discontinued upon the neurologist’s diagnosis. Diphenhydramine and benztropine were started to counteract extrapyramidal symptoms.
Within 24 hours, neurologic symptoms improved strikingly.
At discharge, the patient was able to walk without assistance and had normal facial expressions. The tremor had ceased.
At 6-week follow-up, neurologic symptoms had not returned.
Our patient’s complaints encompassed the full range of extrapyramidal side effects—akathisia (leg restlessness), trouble swallowing and drooling (acute dystonic reaction), tremor, cogwheel rigidity, and dysarthria (parkinsonism).
Of new cases of parkinsonism among a series of 95 patients seen at a geriatric clinic, 51% were given a diagnosis of DIP.6 In a large, prospective study by Bateman and colleagues in northern Great Britain, the incidence of metoclopramide-induced dystonia was 1 in 213; akathisia, 1 in 320; and DIP, 1 in 512.7 The incidence of prochlorperazine-induced dystonia was 1 in 702, akathisia 1 in 937, and parkinsonism 1 in 312. Most retrospective cases of metoclopramide-induced parkinsonism occur in the elderly (older than 60 years).5,8,9
Parkinsonism develops when the striatal dopamine levels fall below 80% of expected (normal) values. This may explain why certain populations in whom the dopamine level is already low, such as the elderly, may be more susceptible to DIP.9
It is difficult to discern which anti-emetic was responsible for our patient’s symptoms; both may be guilty. In the time-line of the case, symptoms manifested when prochlorperazine was started and appeared to have been compounded by addition of metoclopramide. The literature shows that both medications can produce extrapyramidal reactions and parkinsonism.
Symptoms of DIP usually resolve within weeks or months in most patients. In fact, problems that persist beyond 6 months after the medication is withdrawn should raise suspicion of primary Parkinson’s disease or a permanent sequela, such as tardive dyskinesia.3,5
In short, failure to diagnose and treat DIP prolongs the patient’s suffering, which could be relieved by doing something as simple as stopping the agents in question.