What is the next step in managing a patient with severe itching and formication?

Management of Formication (Sensation of Bugs Crawling on Skin)

The next step in managing a patient complaining of itching and feeling like bugs are crawling on her skin should be a thorough evaluation for delusional infestation, including screening for substance use, medication side effects, and underlying medical conditions, followed by appropriate psychiatric referral if primary causes are ruled out. 1, 2, 3

Initial Assessment

Key History Elements to Obtain:

• Duration and characteristics of the sensations
• Presence of visible skin lesions or rashes
• Recent medication changes or new prescriptions
• History of substance use (particularly cocaine, amphetamines)
• Psychiatric history
• Medical conditions (diabetes, renal disease, liver disease, malignancy)
• Recent travel history
• Exposure to potential infestations

Physical Examination Focus:

• Careful skin examination for evidence of:
  • True infestation (scabies, lice, etc.)
  • Rashes or lesions
  • Self-inflicted excoriations
  • Evidence of substance use (track marks, nasal septum changes)

Diagnostic Approach

Rule Out True Infestations:

• Consider skin scraping or biopsy if any suspicious lesions
• Examine any "specimens" the patient may bring (the "matchbox sign")

Laboratory Testing:

• Complete blood count
• Comprehensive metabolic panel (liver and kidney function)
• Thyroid function tests
• Drug screening (critical for detecting substance-induced formication) 3

Management Algorithm

1. If evidence of true infestation is found:

   • Treat according to specific infestation guidelines 4

2. If substance use is identified:

   • Address the substance use disorder as primary treatment
   • Explain the connection between substance use and formication 2, 3
   • Refer to addiction treatment services

3. If medication-induced formication is suspected:

   • Review all medications for potential causative agents
   • Common culprits include anti-Parkinsonian agents, antidepressants, stimulants, and antiepileptics 5
   • Consider medication adjustment in consultation with prescribing physician

4. If underlying medical condition is identified:

   • Treat the primary condition (renal disease, liver disease, etc.)
   • Provide symptomatic relief for pruritus 4

5. If primary delusional infestation is suspected:

   • Psychiatric referral for evaluation and treatment
   • Consider antipsychotic medication (olanzapine has shown efficacy) 1
   • Establish therapeutic alliance and avoid confrontational approach

Symptomatic Management

For Pruritus Relief:

• Topical treatments:

  • Emollients and moisturizers
  • Medium-potency topical corticosteroids for limited periods 4
  • Topical antihistamines (use with caution due to sensitization risk)

• Oral medications:

  • Hydroxyzine 25mg three to four times daily for adults 6
  • Non-sedating antihistamines for daytime use
  • Consider gabapentin or pregabalin for neuropathic symptoms 4

Common Pitfalls to Avoid

1. Dismissing the patient's concerns - Even if no physical cause is found, the sensations are real to the patient

2. Confrontational approach - Directly challenging the patient's beliefs can damage therapeutic relationship

3. Overlooking substance use - Up to 33% of patients with delusional infestation may have positive drug screens but not disclose use 3

4. Missing secondary causes - Always rule out medical conditions, medications, and substances before diagnosing primary delusional disorder

5. Inadequate follow-up - These patients require consistent monitoring and support

Special Considerations

• Patients with formication often have poor insight into their condition
• Building trust is essential for treatment adherence
• A non-judgmental, empathetic approach improves outcomes
• Consider involving family members or caregivers with patient permission
• Document findings carefully, including any specimens brought by the patient

By following this systematic approach, you can effectively manage patients presenting with formication while addressing both the underlying causes and providing symptomatic relief.