caused the reaction is introduced last, if at all. If all
the other drugs are re-introduced successfully, bar
this suspected culprit drug then the assumption can
be made that it caused the reaction and the patient
does not need to be rechallenged with it.
• The drugs are introduced sequentially and additively.
They can be started in small doses which are
increased over 3-4 days until normal therapeutic
doses are attained. It has to be stressed that this
incremental dosing is not a desensitisation regimen,
but is based on a theory that the total dose of the
drug ingested affects the extent of the disease.
There is no evidence at this stage to support this
approach or any other for that matter.
• Monitoring is critical to detect any reaction early. The
parameters that are monitored are the patient’s subjective
feelings of being unwell. These can include a
sore throat, itchy or burning eyes, itchy skin and
fever. Objective changes of the skin and mucosa may
lag behind as do abnormal laboratory blood parameters.
• If signs of any reaction are noted then the most
recently introduced drug is stopped immediately and
the patient is monitored closely. This drug is not reintroduced
again. Further alternative drug re-introduction
is only resumed once the patient has reached
baseline parameters again.
• For tuberculosis rechallenge, the patient must be
started on two antituberculosis drugs to which they
have not previously been exposed plus the first drug
of the rechallenge regimen. This is to avoid the development
of resistance. Delay in getting the patient to
a full complement of drugs increases the risk of
developing resistance.