eMedicine Specialties > Dermatology > Psychocutaneous Diseases
Delusions of Parasitosis: Treatment & Medication
Updated: Feb 12, 2008
- Overview
- Differential Diagnoses & Workup
- Treatment & Medication
- Follow-up
Treatment
Medical Care
The only clear method to clear the delusion that underlies DP is the administration of psychotropic medications. However, the disease can remit on its own. If the sensation of itch is related to some actual disease or substance use rather than a monosymptomatic hypochondriacal psychosis, the disease can be treated, or the substance inducing the sensation can be eliminated.
It is vitally important that the practitioner does not "use the delusion" to encourage the patient to accept certain treatments. While getting the patient to take a medication, such as risperidone, may help the condition, telling them that it is a medication that "kills the parasites", reinforces and validates the delusion. Even giving the patient a course of topical permethrin "just in case" may strengthen the delusion and make it that much more difficult later on. Every DP patient can recount the visit on which his or her suspicions of infestation were "confirmed."
Serotonergic antidepressants may have a role in the treatment of these patients.15,16
Reichenberg et al17 reported on a patient whose DP was cured overnight by having him stop taking cetirizine and doxepin (25 mg), as well as any over-the-counter medications.
Rocha and Hara18 reported that aripiprazole at 15 mg for 8 weeks and then 7.5 mg/d was effective for DP treatment. They stated:
Szepietowski et al19 sent out 172 specially designed questionnaires to dermatologists regarding DP patients; 118 responded. The questions and resulting percentages are as follows:Aripiprazole has a unique pharmacologic profile that is different from other atypical antipsychotic drugs. It is considered a partial dopaminergic agonist acting on both postsynaptic dopamine D2 receptors and presynaptic autoreceptors. It acts as a weak stimulator (so-called “partial” agonist) at dopamine D2 receptors, with the potential for exerting either antagonistic (inhibitory) or agonistic (stimulating) effects, depending on the sensitivity of the receptors and availability of dopamine, its natural agonist in the brain. In addition, aripiprazole displays partial agonism at serotonin (1A) receptors and antagonism at serotonin (2A) receptors.
- Had seen at least one patient with DP - 84.7%
- Had 1-2 cases of DP over the preceding 5 years - 33%
- Had seen 3-5 such patients over the preceding 5 years - 28%
- Had diagnosed no cases of DP during the past 5 years - 23%
- Had more than 10 patients with DP over the past 5 years - 7%
- Were currently treating a patient with DP - 20%
- Always request a psychiatric opinion about their patients with DP - 40.75%
- Often ask for a psychiatric opinion about their patients with DP 28.8%
- Use their own pharmacological treatment, mostly sedatives and anxiety-relieving drugs - 15.3%.
Consultations
A psychiatrist should be consulted if the dermatologist cannot or will not prescribe the necessary medications. Most patients with DP are reluctant to see a psychiatrist, and the dermatologist may be more successful in giving the referral if they have gained the patient's trust after several clinic visits instead of immediately after meeting the patient.
Medication
The current treatment of choice is risperidone20,21 or olanzapine.22 The older treatment of choice is pimozide.23
The most common adverse effects of pimozide are extrapyramidal symptoms, including stiffness and, occasionally, a special inner sense of restlessness called akathisia. Effective treatment of such extrapyramidal reactions includes benztropine 1-2 mg up to 4 times daily as needed or diphenhydramine 25 mg 3 times daily.
Antipsychotics
Used to treat psychoses.
Risperidone (Risperdal)
Binds to dopamine D2 receptor with 20 times lower affinity than for 5-HT2 receptor. Improves negative symptoms of psychoses and reduces incidence of extrapyramidal adverse effects.
Adult
1-2 mg qd initially
Pediatric
Not indicated
Coadministration with carbamazepine may decrease effects; risperidone may inhibit effects of levodopa; clozapine may increase risperidone levels.
Hypersensitivity
Pregnancy
C - Fetal risk revealed in studies in animals but not established or not studied in humans; may use if benefits outweigh risk to fetus
Precautions
May cause extrapyramidal reactions, hypotension, tachycardia, and arrhythmias
Olanzapine (Zyprexa)
May inhibit serotonin, muscarinic and dopamine effects.
Adult
2.5 mg/d
Pediatric
Not indicated
Fluvoxamine may increase effects of olanzapine; antihypertensives may increase risk of hypotension and orthostatic hypotension; levodopa, pergolide, bromocriptine, charcoal, carbamazepine, omeprazole, rifampin, and cigarette smoking may decrease effects of olanzapine.
Documented hypersensitivity
Pregnancy
C - Fetal risk revealed in studies in animals but not established or not studied in humans; may use if benefits outweigh risk to fetus
Precautions
Caution in narrow-angle glaucoma, cardiovascular disease, cerebrovascular disease, prostatic hypertrophy, seizure disorders, hypovolemia, and dehydration
Pimozide (Orap)
Antipsychotic of the diphenylbutylpiperidine class. It is used to treat DP and Tourette disorder.
Adult
1-12 mg/d
Pediatric
<12 years: Not established
>12 years: Administer as in adults
Increases toxicity of MAOIs, alfentanil, CNS depressants, and guanabenz
Documented hypersensitivity; history of cardiac arrhythmias or long QT syndrome; presently receiving macrolide antibiotics
Pregnancy
C - Fetal risk revealed in studies in animals but not established or not studied in humans; may use if benefits outweigh risk to fetus
Precautions
ECG recommended at initiation and regular intervals thereafter; careful observation for extrapyramidal symptoms, especially in geriatric patients
More on Delusions of Parasitosis |
| Overview: Delusions of Parasitosis |
| Differential Diagnoses & Workup: Delusions of Parasitosis |
 Treatment & Medication: Delusions of Parasitosis |
| Follow-up: Delusions of Parasitosis |
| References |
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References
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Further Reading
Keywords
DP, DOP, insect infestation, matchbox sign, monosymptomatic hypochondriacal psychosis, delusion of infestation, delusional parasitosis, delusional infestation, folie à deux, folie partagé, morgellons disease.
