Drug Interaction Report

ADJUST DOSING INTERVAL: Systemic antihistamines may diminish the response to the trichophyton diagnostic skin test and lead to falsely insignificant or false-negative results. The proposed mechanism is inhibition of histamine release in the skin leading to suppression of the wheal and flare response. This interaction has been documented in numerous studies examining allergenic extracts and different antihistamines, but clinical data with the trichophyton diagnostic skin test are not readily available.

MANAGEMENT: The labeling for the trichophyton skin test recommends avoiding use of antihistamines for at least 24 hours prior to skin testing, though longer may be required depending on the specific antihistamine in question. Consultation with the labeling of the individual antihistamine as well as any relevant local and/or national guideline(s) is advisable.

GENERALLY AVOID: Alcohol may potentiate some of the pharmacologic effects of CNS-active agents. Use in combination may result in additive central nervous system depression and/or impairment of judgment, thinking, and psychomotor skills.

MANAGEMENT: Patients receiving CNS-active agents should be warned of this interaction and advised to avoid or limit consumption of alcohol. Ambulatory patients should be counseled to avoid hazardous activities requiring complete mental alertness and motor coordination until they know how these agents affect them, and to notify their physician if they experience excessive or prolonged CNS effects that interfere with their normal activities.