Rifampicin

inhibition of mycobacterial RNA synthesis

• mechanism of action: inhibits bacterial DNA dependent RNA polymerase preventing transcription of DNA into mRNA
• potent liver enzyme inducer
  • Rifampicin is a P450 enzyme inducer and will therefore increase the metabolism of warfarin, therefore decreasing the INR.
• hepatitis, orange secretions
• flu-like symptoms

Isoniazid

inhibition of myobacterial cell wall synthesis

• mechanism of action: inhibits mycolic acid synthesis
• peripheral neuropathy: prevent with pyridoxine (Vitamin B6)
• Can cause lupus
• hepatitis, agranulocytosis
• liver enzyme inhibitor

Pyrazinamide

• mechanism of action: converted by pyrazinamidase into pyrazinoic acid which in turn inhibits fatty acid synthase (FAS) I
• hyperuricaemia causing gout
• arthralgia, myalgia
• hepatitis (most likely to cause hepatitis out of the TB drugs)

Ethambutol

inhibition of myobacterial cell wall synthesis