Co-trimoxazole desensitisation
Only for use on the advice of Micro/ID
Desensitisation to co-trimoxazole can be undertaken in certain patients, who have experienced an adverse reaction to co-trimoxazole, when alternatives are considered unsuitable.
Patients should be referred to the Infectious Disease (ID) team for co-trimoxazole desensitisation and ID will oversee the process. The desensitisation process should occur either as in-patient under ID team supervision or as an out-patient under the ID team in Day Unit.
Symptoms of co-trimoxazole hypersensitivity and suggested management
|
Grade/symptoms |
Management |
|
GRADE 1 Erythema |
Continue co-trimoxazole prophylaxis or treatment with careful and repeated observation and follow-up. Provide symptomatic treatment, such as antihistamines. |
|
GRADE 2 Diffuse maculopapular rash,dry desquamation |
Continue co-trimoxazole prophylaxis or treatment with careful and repeated observations and follow-up. Provide symptomatic treatment, such as antihistamines. |
|
GRADE 3 Vesiculation, mucosal ulceration |
Discontinue co-trimoxazole until the adverse effect has completely resolved (usually two weeks), and then consider reintroduction or desensitisation. |
|
GRADE 4 Exfoliative dermatitis, Stevens-Johnson syndrome, erythema multiforme, moist desquamation, toxic epidermal necrolysis and drug rash with eosinophilia and systemic symptoms (DRESS) |
Co-trimoxazole should be permanently discontinued. The patient’s allergy status (including the nature, severity and date of the reaction) should be updated on EPR and communicated with the GP. These patients should not be re-challenged with co-trimoxazole. |
When to attempt desensitisation
Desensitisation CAN be attempted two weeks following a non-severe reaction (Grade 1, 2 or 3) to co-trimoxazole which has prompted discontinuation of the drug.
When NOT to attempt desensitisation
Desensitisation should NOT be attempted in a patient who has had the following reactions to co-trimoxazole, sulfadiazine and sulfasalazine:-
- Any Grade 4 reaction (listed in table above)
- Anaphylaxis/anaphylactoid reaction
Desensitisation Procedure
- Ensure this takes place in acute clinical setting where staff are trained in the management of anaphylaxis and emergency drugs are readily available.
- Take verbal consent from the patient and explain the procedure and potential risk of recurrence of reaction. Advise the patient they may need to attend clinic daily for 7 days to complete the desensitisation.
- Perform observations. There is no need to routinely insert an intravenous cannula.
- Prescribe and administer co-trimoxazole, according to the table below
- If the patient is being desensitised to receive prophylaxis and target dose is 480mg then they do no need to be prescribed the 960mg test dose.
- Observe for 1 hour in in-patient setting. Only perform observations if clinical concern. The patient can then be discharged home to return for the next dose on the following day.
|
|
Total oral dose of co-trimoxazole |
Volume of co-trimoxazole oral suspension (240mg/5ml) |
|
Day 1 |
96 mg |
2ml |
|
Day 2 |
192 mg |
4ml |
|
Day 3 |
288 mg |
6ml |
|
Day 4 |
384 mg |
8ml |
|
Day 5 |
480 mg |
10ml of 240mg/5ml suspension OR 1 x 480mg tablet |
|
Day 6 onwards |
960 mg |
20ml of 240mg/5ml suspension OR 2 x 480mg tablets |
Interpretation of results
-
If a severe reaction occurs: the desensitisation regimen is terminated and the patient is labelled on EPR "allergy to co-trimoxazole"*.
-
If a minor reaction occurs: repeat the same step for an additional day.
-
If the reaction subsides, advance to the next step.
-
If the reaction worsens, the desensitisation regimen is terminated and the patient is labelled on EPR "allergy to co-trimoxazole"*.
-
Inform the patient's GP of the results of the desensitisation, indicating whether the patient is tolerant or intolerant of co-trimoxazole.
If co-trimoxazole is stopped for more than one day, the desensitisation regimen restarts again from Day 1 of the regimen.
*If patient has "allergy to co-trimoxazole" then include the nature, severity and date of the reaction on EPR and communicate this to the patient's GP.
References
WHO 2006. Guidelines on Co-trimoxazole Prophylaxis for HIV related infections among children, adolescents and adults. Recommendations for a public health approach. WHO Guidelines. Pages 24-25