Interventions for Tuberculosis Control and Elimination 2002

necessary). If the event occurs in the continuation phase when the patient
is on isoniazid plus ethambutol, the latter should be replaced by thioacetazone
or rifampicin.
The patient with vestibulo-cochlear toxicity
Vestibulo-cochlear toxicity is virtually always due to streptomycin. It is
often, but not always, dose-dependent. Thus, it should first be checked
whether the dosage given is appropriate to weight and age (toxicity increases
with both). If the dose cannot be reduced or if dose reduction fails to
improve the symptomatology, streptomycin should be stopped and not be
given again (unless the drug resistance pattern makes its use imperative).
As streptomycin is usually given only in the intensive phase as a fourth
companion drug, it can be stopped without replacement. Streptomycin
should never be given to pregnant women because of the potential risk of
causing deafness in the unborn child.
The patient with neurologic symptoms
A distinction should be made between peripheral and central nervous system
toxicity from anti-tuberculosis medications.
Peripheral neuropathy, presenting as paresthesia, such as tingling and
numbness, starting at the feet with proximal spread is the usual manifestation.
408 Myalgias, weakness, and ataxia may accompany these symptoms.
Peripheral neuropathy is usually due to isoniazid, is rare and occurs usually
only in malnourished or alcohol-dependent patients. Pyridoxine is
effective in treating this condition, but the dosage for treatment should not
exceed 50 mg per day, as there might be antagonism with isoniazid, 108
although the clinical relevance of this antagonism is not clear.
Infrequently, toxic psychosis and epileptic convulsions may occur with
isoniazid, and very rarely, in patients with signs of malnutrition or malabsorption,
a pellagroid syndrome (with dermatitis, diarrhea, and dementia)
has been reported. Pyridoxine is usually effective for treating such cases.
The patient with hypersensitivity reactions
or muco-cutaneous signs and symptoms of toxicity
Cutaneous adverse drug events, ranging from pruritus, to rashes, and most
severely to toxic epidermal necrolysis, sometimes accompanied by fever,
may be caused by thioacetazone, isoniazid, rifampicin, streptomycin, or
89