You have been assigned to care for Mr. U, a 32-year-old man who has been diagnosed with TB. He goes to the public health department daily to receive his dose of isoniazid and rifampin. Ms. O is your clinical instructor for the day. She has a reputation for asking a lot of questions about the patient's medications. Ms. O asks you the following questions.

 

1.    "How do the drugs isoniazid and rifampin work? Why has Mr. U been prescribed two drugs to treat his tuberculosis?" How would you answer this question?

2.    "What is the most common adverse effect of each drug? How will you assess for these?" How would you respond? 

1.

Rifampin (RIF) is belongs to Rifamycin that inhibits RNA synthesis by targeting RNA polymerase. Rifampin enters bacilli and binds to the beta subunit of DNA dependent polymerase to form a sable drug-enzyme complex. This binding suppresses formation of RNA synthesis.

Isoniazid (INH) inhibits mycolic acid synthesis leading to bacterial cell death. Mycolic acid is a component of mycobacterial cell wall.

He was prescribed with two drugs because combination of isoniazid and rifampin provides basis for short course therapy. These two are combined to as pharmacology approach to simulate MTB infection, resistance acquisition, and antibiotic treatment so that we can predict INH- and RIF-resistance. 

2. Rifampicin most common adverse effect is rash (0.8%). Other side effects are fever, nausea and vomiting and rarely hepatitis. Isoniazid common adverse effect is increase in serum aspartate and alanine transaminase level. Other side effect are peripheral neuritis if isoniazid is not taken with pyrodixine.