Skip to main content

Advertisement

Nonirritant concentrations and amount of active ingredient in drug patch tests optimal concentrations for DPTs

Background

Drug patch tests (DPTs) with medications suspected of causing an allergic reaction represent a method of diagnostic testing that is low risk, as DPTs can reproduce delayed hypersensitivity to drugs and entail only a moderate re-exposure of patients to potential offending drugs. We assessed the non-irritating concentration of DPTs to determine the amount of active ingredient (AI) contained in the drugs used in the tests.

Method

From a retrospective, single-center study of all patients treated during a 6-year period for etiological investigations following a drug eruption, each potentially responsible drug was tested from the commercially available preparation diluted to 30% of its concentration in water, petrolatum, or alcohol. Data collection was performed with a customized computer database. For each type of DPT studied, the numbers of positive and negative tests were recorded. The amount of AI contained in the DPT (as a percentage) was then calculated after weighing each tablet.

Results

Of the 5,558 DPTs studied, all were nonirritant. The average concentration of AI was 9.8%; 25% of DPTs had an AI concentration less than 2%, and 25% displayed an AI concentration above 16%. The AI concentration ranged from 0.05% (digoxin) to 30% (paracetamol lyophilisate).

Discussion

The actual concentrations of the AI in DPTs done at 30% of the commercially available form varied from 0.05% to 27.08% when tablets were used. Any report of the results of a DPT must give the exact concentration of the AI applied.

Conclusion

These data provide thresholds for the non-irritating concentration of 89 different drugs, and will help to standardize DPT methods.

Author information

Correspondence to Annick Barbaud.

Rights and permissions

Reprints and Permissions

About this article

Verify currency and authenticity via CrossMark

Keywords

  • Digoxin
  • Paracetamol
  • Active Ingredient
  • Actual Concentration
  • Allergic Reaction