Specific allergies

ALLERGIES TO PENICILLINS

Z88.0

DESCRIPTION

Patients may present with immediate (e.g. anaphylaxis, bronchospasm, angioedema) or delayed reactions (most commonly maculopapular rash without systemic involvement; rarely SJS/TEN or other systemic reactions).

GENERAL AND SUPPORTIVE MEASURES

Stop penicillin.

MEDICINE TREATMENT

If an antibiotic is still required, treat with a suitable alternative antibiotic class according to the condition.

Milder infections e.g. upper respiratory tract infections, impetigo, mild cellulitis:

  • Macrolide, e.g. Azithromycin, oral, 10 mg/kg/day for 3 days.

Severe infections e.g. osteomyelitis, pneumonia:

  • Third generation cephalosporin, provided there is no history of immediate hypersensitivity (see below, cross-reactivity of other β-lactams).

Alternative antibiotics for Gram positive infections:

  • Clindamycin, oral, 6 mg/kg/dose 6 hourly.

OR

  • Vancomycin, IV, 15 mg/kg 8 hourly.

Urinary Tract Infection

  • Neonates: Ciprofloxacin, oral, 6 mg/kg/dose 12 hourly.
  • Infants: Ciprofloxacin, oral, 6 mg/kg/dose 8 hourly.
  • > 1 year of age: Ciprofloxacin, oral, 10 mg/kg/dose 12 hourly.

Prophylaxis in rheumatic heart disease or post splenectomy, consider:

  • Macrolide e.g.
    • < 11 years: Azithromycin, oral, 10 mg/kg/day, 3 times weekly.
    • ≥ 11 years: Azithromycin, oral 250 mg daily.

LoEIII [2]

Cross-reactivity of other β-lactams in patients with penicillin allergy
The risk of cross-reactivity to cephalosporins in penicillin allergic patients is low. Consequently, only avoid oral cephalosporins in patients with a history of anaphylaxis to penicillin.
In hospitalised patients, and in those with mild reactions such as rash to aminopenicillin, cephalopsporins should not be avoided if indicated for infection. If concerned, discuss with expert and/or consider test dose.

Risk of cross-reactivity is very low with carbapenems, and these agents can be used without allergy assessment in penicillin allergic patients.

If no alternative antibiotic is available, consider desensitisation after consultation with a specialist. Desensitisation to be done by a specialist, in a tertiary facility.

REFERRAL

  • In cases where desensitisation is considered.

Consult a specialist:

  • For alternative antibiotics in all patients with severe immediate reactions.

ALLERGIES TO SULPHONAMIDES

Z88.2

DESCRIPTION

The commonest sulphonamide allergies are related to co-trimoxazole, especially when used in HIV-infected patients for P. jirovecii treatment and/or prophylaxis.

Patients may present with:

  • a morbilliform or maculopapular rash only, usually within a few days of starting treatment (most common presentation),
  • a rash with fever, which may progress to
  • a drug-induced rash with eosinophilia and systemic symptoms (DRESS) usually with hepatitis (usually within 1–2 weeks of treatment commencement)
  • SJS/TEN, or
  • an immediate hypersensitivity reaction (rare).

GENERAL AND SUPPORTIVE MEASURES

Stop the sulphonamide-containing drug. Severe cutaneous drug reactions with or without organ involvement require admission and specialist review to optimise supportive management. See SJS/TEN .

MEDICINE TREATMENT

Options for HIV-infected patients requiring treatment for P. jirovecii pneumonia with history of mild reaction, e.g. rash to prior co-trimoxazole exposure:

  • Dapsone, oral, 2 mg/kg daily.
    • Maximum dose: 100 mg (1 tablet) daily.
    • Note: Dapsone is a sulphone, not a sulphonamide, but there are cases of cross-reactivity with sulphonamide allergy but reactions are usually mild. Avoid dapsone if there is a history of anaphylaxis, SJS/TEN, or rash with systemic involvement.

If no alternative antibiotic is available, consider desensitisation after consultation with a specialist. Desensitisation to be done by a specialist in a tertiary facility.

REFERRAL

  • In cases where desensitisation is considered. Consult a specialist.
  • For alternative antibiotics in all patients with severe immediate reactions.