Hello Susan,

Thank you for asking your query at DoctorSpring.

Change or substitution of TB medication should be considered only if the adverse effects are very serious like sever liver dysfunction or life threatening allergic reaction. I do understand fatigue and the abdominal discomfort could be troubling, but unfortunately he will have to move on with it. Fatigue should improve with nutritious food and rest. Abdominal pain could be due to Drug induced gastritis for which he might be getting anti ulcer / PPI drugs like Omeprazole.

Any unnecessary discontinuation or change in the drug will put your brother in risk for a resistant TB infection called MDRTB (Multi drug resistant TB). That is the reason why change in medication is not recommended. All the medications are of 6 months duration (min) and has its own side effects. Rifamipicin and Isoniazid are the most commonly used and efficient ones among them.
So changing drugs will put you 1) risk for MDRTB 2) slow resolution 3)More treatment duration 4) other side effects may occur
Most of the patients suffer from some kind of side effects. But that should not deter them from taking the drug for successful completion of the treatment. Your brother in law needs motivation and support from you and I feel you should not encourage the idea of ‘changing’ medication at all !

I hope this helps
Please feel free to ask follow-up questions.
Thank you