The development of subsensitivity to chlorpheniramine.
The Journal of Allergy and Clinical Immunology
|July 1, 1985
Summary
Subsensitivity to antihistamines, like chlorpheniramine, develops within 7 to 21 days of treatment. This diminished drug effect, observed via skin prick tests (PSTs), cannot be fully reversed by increasing the dosage.
Area of Science:
- Pharmacology
- Immunology
- Dermatology
Background:
- Antihistamines are crucial for managing allergic reactions.
- Understanding the development of drug tolerance is essential for effective long-term treatment.
Purpose of the Study:
- To investigate the emergence of subsensitivity to antihistamines during therapy.
- To determine if increased dosage can overcome this diminished drug response.
Main Methods:
- A double-blind crossover study involving 10 subjects receiving chlorpheniramine or placebo.
- Titrated prick skin tests (PSTs) to histamine and antigen were performed at intervals.
- Wheal area, serum drug levels, and response to dosage increase were measured.
Main Results:
- Maximal skin test suppression occurred on days 3 or 7, with significantly less suppression by day 21.
- Doubling the chlorpheniramine dose did not restore maximal suppression.
- No significant correlation was found between serum drug levels and PST suppression.
Conclusions:
- Subsensitivity to antihistamines develops between 7 and 21 days of therapy.
- This tolerance cannot be fully overcome by doubling the dose.
- The mechanism may involve increased histamine H1 receptor numbers rather than induced metabolism.
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