Pseudoephedrine


Many drugs contain cathecholamine derivatives (local anesthetics, eye drops with neosynephrine, nasal vasoconstrictives).
 
Incidence
Low.
 
Clinical manifestations
Urticaria, eczema (oral absorption of pseudoephedrine), fixed drug eruption, scarlatin-like rash.
 
Acute conjunctivitis with eczema of the eyelids (neosynephrine containing eye drops).
 
Diagnostic methods
Cutaneous testing.
 
Prick-tests and patch-tests with pseudoephedrine 1%, 5% in water or pet. (patch-tests).
 
Mechanisms
Immediate hypersensitivity is exceptional.
 
Delayed contact hypersensitivity is more frequent.
 
Mechanism is unknown in toxic shock syndrome and in most rashes.
 
Management
Avoidance.
 
Cross-reactivity may exist among cathecholamine derivatives.
 
There are 2 types of derivatives:
  • ephedrine, pseudoephedrine and norephedrine derived from a molecular structure of phenyl propanolamine type.These molecules have a very close structure and can cross-react.
     
  • epinephrine and phenylephrine do not seem to cross-react with the first group. Thus sensitization to pseudoephedrine does not contra-indicate the use of eye drops containing neosynephrine and the use of epinephrine containing local anesthetics.

References

  1. Thomas P, Rueff F, Pryzbilla B, "Severe allergic contact blepharoconjunctivitis from phenylephrine in eye drops, with corresponding T-cell hyperresponsiveness in vitro", Contact. Dermatitis, 1998; 38: 41-3
  2. Rochina A, Burches E, Morales C, Braso J.V, Pelaez A, "Adverse reaction to pseudoephedrine", J. Invest. Allergol. Immunol., 1995; 5: 235-6
  3. Tomb R.R, Lepoittevin J.T, Espinassouze F, Heid E, Foussereau J, "Systemic contact dermatitis from pseudoephedrine", Contact. Dermatitis., 1991; 24: 86-8
  4. Taylor B.J, Duffill M.B, "Recurrent pseudo-scarlatina and allergy to pseudoephedrine hydrochloride", Br. J. Dermatol., 1988; 118: 827-9

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