Which four drugs constitute the RIPE regimen?

• A. Rifampin, Isoniazid, Pyrazinamide, Ethambutol
• B. Rifampin, Isoniazid, Ethambutol, Streptomycin
• C. Isoniazid, Pyrazinamide, Ethambutol, Levofloxacin
• D. Rifampin, Isoniazid, Pyrazinamide, Streptomycin

Answer: (A)

RIPE is the standard initial four-drug combo used for drug-susceptible tuberculosis because it combines agents with different mechanisms to rapidly kill bacilli and prevent resistance. The four drugs are rifampin, isoniazid, pyrazinamide, and ethambutol. Rifampin inhibits bacterial RNA synthesis, making it highly bactericidal. Isoniazid blocks the production of mycolic acids in the cell wall, weakening the bacteria. Pyrazinamide works especially in acidic conditions to disrupt energy metabolism and membrane function, helping shorten therapy. Ethambutol interferes with cell wall synthesis by inhibiting arabinogalactan production, adding another mechanism and delaying resistance. Together, they provide strong, broad coverage in the initial intensive phase of treatment. Other drugs like streptomycin or levofloxacin appear in different regimens or contexts (e.g., resistance scenarios), so they are not part of the standard RIPE combination.