Can carbidopa (CARBIDOPA)-levodopa cause a rash?

Carbidopa-Levodopa and Skin Rash

Yes, carbidopa-levodopa can cause skin rash, which is specifically listed as an adverse reaction in the FDA drug label, and there are documented cases of allergic reactions specifically to the carbidopa component.1

Evidence from FDA Drug Label

The official FDA drug label for carbidopa-levodopa clearly documents skin reactions among its adverse effects, including:

• Rash
• Increased sweating
• Pruritus (itching)
• Urticaria (hives)
• Henoch-Schönlein purpura
• Bullous lesions (including pemphigus-like reactions)
• Angioedema 1

Specific Case Evidence

A documented case report describes a 77-year-old woman with Parkinson's disease who developed an allergic reaction specifically to carbidopa, manifesting as:

• Pruritic generalized rash
• Conjunctival injection
• Rhinorrhea
• Excessive sweating
• Hypertension

Importantly, these symptoms occurred immediately after carbidopa/levodopa administration regardless of manufacturer. The symptoms resolved completely with antihistamine and steroid treatment, and did not recur when the patient was switched to benserazide/levodopa, confirming that the allergic reaction was specific to carbidopa rather than levodopa. 2

Management of Carbidopa-Levodopa Skin Reactions

If a patient develops a rash while taking carbidopa-levodopa:

1. Assess severity:

   • Mild localized rash: May be monitored with antihistamines
   • Extensive rash or signs of systemic reaction: Requires immediate medical attention
   • Any bullous lesions or exfoliative reactions: Immediate discontinuation is recommended

2. Treatment options:

   • Topical therapies (lotions or glucocorticoids)
   • Systemic antihistamines
   • Short courses of systemic steroids for more severe reactions

3. For severe reactions:

   • Temporary interruption or dose reduction of carbidopa-levodopa
   • Consider switching to an alternative formulation (e.g., benserazide/levodopa) if the reaction is specifically to carbidopa 2

Clinical Considerations

• The rash may be part of a hypersensitivity reaction that could involve other symptoms
• Patients with a history of drug allergies may be at higher risk
• The onset of rash can occur at any time during treatment
• Patients should be educated about this potential side effect and instructed to report any skin changes promptly

Conclusion

While carbidopa-levodopa is generally well-tolerated, healthcare providers should be aware that skin rash is a documented adverse effect. In cases of suspected allergic reaction, careful evaluation is needed to determine whether the reaction is to carbidopa, levodopa, or an excipient in the formulation, as this will guide appropriate management decisions.