eMedicine Specialties > Dermatology > Psychocutaneous Diseases

Delusions of Parasitosis: Treatment & Medication

Author: Noah S Scheinfeld, MD, JD, FAAD, Assistant Clinical Professor, Department of Dermatology, Columbia University; Consulting Staff, Department of Dermatology, St Luke's Roosevelt Hospital Center, Beth Israel Medical Center, New York Eye and Ear Infirmary; Private Practice
Contributor Information and Disclosures

Updated: Feb 12, 2008

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:

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.

Szepietowski et al19 sent out 172 specially designed questionnaires to dermatologists regarding DP patients; 118 responded. The questions and resulting percentages are as follows:

  • 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.

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.

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

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.

Contributor Information and Disclosures

Author

Noah S Scheinfeld, MD, JD, FAAD, Assistant Clinical Professor, Department of Dermatology, Columbia University; Consulting Staff, Department of Dermatology, St Luke's Roosevelt Hospital Center, Beth Israel Medical Center, New York Eye and Ear Infirmary; Private Practice
Noah S Scheinfeld, MD, JD, FAAD is a member of the following medical societies: American Academy of Dermatology
Disclosure: Nothing to disclose.

Medical Editor

Franklin Flowers, MD, Chief, Division of Dermatology, Professor, Department of Medicine and Otolaryngology, University of Florida College of Medicine
Franklin Flowers, MD is a member of the following medical societies: American College of Mohs Micrographic Surgery and Cutaneous Oncology, Lipoplasty Society of North America, Southwest Pediatric Nephrology Study Group, Southwestern Oncology Group, Southwestern Surgical Congress, Special Operations Medical Association, State Medical Society of Wisconsin, Swedish Medical Association, Sydenham Society, Tennessee Medical Association, Tennessee Radiological Society, Texas Medical Association, Texas Pediatric Society, Texas Society of Plastic Surgeons, Undersea and Hyperbaric Medical Society, Uniformed Services Academy of Family Physicians, United States and Canadian Academy of Pathology, United States Pharmacopeial Convention, US Virgin Islands Medical Society, Utah Medical Association, Vermont State Medical Society, Vestibular Disorders Association, Virginia Society of Otolaryngology-Head and Neck Surgery, West Virginia State Medical Association, Western Occupational and Environmental Medical Association, Western Orthopaedic Association, Western Section American Urological Association, Western Surgical Association, Wilderness Medical Society, World Association of Societies of Pathology and Laboratory Medicine, World Medical Association, World Society for Stereotactic and Functional Neurosurgery, and Wyoming Medical Society
Disclosure: Nothing to disclose.

Pharmacy Editor

David F Butler, MD, Professor of Dermatology, Texas A&M University College of Medicine; Director, Division of Dermatology, Scott and White Clinic; Director Dermatology Residency Training Program, Scott and White Clinic
David F Butler, MD is a member of the following medical societies: Alpha Omega Alpha, American Academy of Dermatology, American Medical Association, American Society for Dermatologic Surgery, American Society for MOHS Surgery, Association of Military Dermatologists, and Phi Beta Kappa
Disclosure: 3M Pharmaceutical Grant/research funds Other; Graceway Pharmaceuticals Grant/research funds Other

Managing Editor

Jeffrey Meffert, MD, Assistant Clinical Professor of Dermatology, University of Texas Health Science Center-San Antonio
Jeffrey Meffert, MD is a member of the following medical societies: American Academy of Dermatology
Disclosure: Nothing to disclose.

CME Editor

Catherine Quirk, MD, Clinical Assistant Professor, Department of Dermatology, Brown University
Catherine Quirk, MD is a member of the following medical societies: Alpha Omega Alpha and American Academy of Dermatology
Disclosure: Nothing to disclose.

Chief Editor

Dirk M Elston, MD, Director, Department of Dermatology, Geisinger Medical Center
Dirk M Elston, MD is a member of the following medical societies: American Academy of Dermatology
Disclosure: Nothing to disclose.

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