Metronidazole


Nitroimidazole derivative used for the treatment of anaerobic infections and trichomonas infections.
 
Incidence
Uncommon.
 
Clinical manifestations
Fever, serum sickness.
 
Bronchospasm.
 
Urticaria, maculopapular rash, fixed drug eruption, pustulosis.
 
Diagnostic methods
1.5 mg of 0.75% metronidazole vaginal gel applied to the vaginal mucosa induced wheals of 6 x 6 mm in one patient and 2.5 x 5 mm in another with severe allergic reactions to metronidazole.
 
Mechanisms
IgE-mediated hypersensitivity is likely in some cases.
 
Management
Cross-reactivity between metronidazole and tinidazole (fixed drug eruption).
 
Desensitization.
 
Two different protocols have been published:
  • 0.0025 mg to 1 000 mg in 8 steps (orally)
     
  • 5 µg to 125 mg intravenously (3h40), then 250 mg, 500 mg, 2 g orally (3 h).

References

  1. Pearlman M.D, Yashar C, Ernst S, Solomon W, "An incremental dosing protocol for women with severe vaginal trichomoniasis and adverse reactions to metronidazole", Am. J. Obstet. Gynecol., 1996 ; 174 (3): 934-6
  2. Knowles S, Chhoudhury T, Shear N.H, "Medronidazole hypersensitivity", Ann. Pharmacother., 1994 ; 28 (3): 325-6
  3. Kurohara M.L, Kwong F.K, Lebherz T.B, Klaustermeyer W.B, "Metronidazole hypersensitivity and oral desensitization", J. Allergy Clin. Immunol., 1991 ; 88 (2): 279-80

As in all diagnostic testing, the diagnosis is made by the physican based on both test results and the patient history.