Journal of the Louisiana State Medical Society
Table 2: Second Generation Antipsychotics Recommended for Delusional Infestations: Comparison of Dosing Schedules and Adverse Effects Medications: generic names Olanzapine Risperidone Ziprasidone Medications: trade names Zyprexa® Risperdal® Geodon® Daily dosing schedule 5 mg po q day hs 2 mg po q day hs
Advance over 2 days from 20 mg bid to 40 mg tid (120 mg/day)
Weight gain
+++
++
0/+
Hyperglycemia
+ +
0 0
0 0
Dyslipidemias
Sedation
++
++
+
Hypotension
+
+ +
0
Anticholinergic effects
+++
+
+++: High effect; ++: Moderate effect; +: Minimal effect; 0: No effect
ups for evidence of parasitosis, psychological counseling, and the use of the newer neuroleptic medications, especially the second-generation or atypical antipsychoticmedications, including olanzapine, risperidone, and ziprasidone. 1,2,16-19 Unlike pimozide and all other first-generation antipsychot- ics, the second-generation antipsychotics carry less risk of precipitating cardiac arrhythmias, especially prolonged QT intervals and torsades de pointes , extra-pyramidal syndromes, and tardive dyskinesias. 1,12-14 Several reports have now confirmed that relatively small daily doses of these atypical antipsychotics or neuro- leptics are dramatically effective in reducing the delusions of infestation. 1,13,14 Some of the atypicals are associated with sedation, weight gain, and hyperglycemia, especially olanzapine; but all have significantly lower potentials for causing cardiac arrhythmias, extrapyramidal syndromes, and tardive dyskinesias than the first generation antipsy- chotics. 1,13,14 Table 2 compares the adverse effects of the second-generation antipsychotics recommended for the management of delusional infestations and their dosing schedules. In 2006, Narumoto and co-investigators reported a case that has now provided significant scientific support for a physiochemical mechanismof dopaminergic and serotoner- gic neurotransmitter dysfunction in delusional infestation and for the continued use of second-generation antipsychot- ics in treating the disorder. 14 In their case, a patient devel- oped delusional infestation following an acute, ischemic stroke in the right temporoparietal region and was treated with risperidone with rapid, dramatic improvement. 14 A pre-treatment single-photon emission computerized tomography (SPECT) scan showed a global decrease in re- gional cerebral blood flow (rCBF), but a post-treatment scan showed marked increase in rCBF in the region of the brain infarct and in the basal ganglia bilaterally. 14 This report was the first objective confirmation using sensitive neuroimaging techniques of the utility of second-generation antipsychotics
in the management of the disorder by increasing rCBF in specific brain regions. 14 In addition, the neuroimaging study demonstrated an association between reduced rCBF and the dysesthesias of delusional infestation and the reversal of dysesthesias with the restoration of rCBF, suggesting an ischemic mechanism for the disorder. 14 Although some reports have suggested that cases of delusional infestation are increasing today, especially in arid and tropical regions where arthropod-borne infectious dis- eases are hyperendemic, most studies have now confirmed a relatively stable incidence rate over time and similar disease demographics worldwide. 15 The management strategies for delusional infestations have, however, changed significantly over time with second-generation, atypical antipsychotics offering safer adverse effect profiles and better prognoses than earlier therapies with first-generation, typical antipsy- chotics. The most effective current management strategies for delusional infestations include empathetic history-taking and active listening to the patient; careful exclusion of true parasitoses, such as mite infestations and cercarial derma- titis, and neurodegenerative or cerebrovascular disorders; and a therapeutic regimen that includes a second-generation neuroleptic agent. REFERENCES 1. Meehan WJ, Badreshia S, Mackley CL. Successful treatment of delusions of parasitosis with olanzapine. Arch Dermatol 2006; 142: 352-355. 2. Donabedian H. Delusions of parasitosis. Clin Infect Dis 2007; 45: 131-134. 3. Wilson JW, Miller HE. Delusion of parasitosis. Arch Dermatol Syphiol 1946; 54: 39-56. 4. Freudenmann RW, Lepping P. Delusional infestation. Clin Microbiol Rev 2009; 22: 690-732. 5. Bourgeois ML, Duhamel P, Verdoux H. Delusional parasitosis: folie à deux and attempted murder of a family physician. Br J Psychaitr 1992; 161: 709-711.
158 J La State Med Soc VOL 166 July/August 2014
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