🦠 Antimycobacterial Drugs for the MCAT: RIPE Therapy and Mechanisms Made Visual
Tuberculosis (TB) is more than just a historical disease—it's an MCAT micro high-yield favorite, especially when it comes to understanding the RIPE drug regimen, mechanisms of action, and resistance patterns.
📚 MCAT Relevance: Tuberculosis in Test Questions
MCAT questions related to TB often show up in:
MCAT Section: Biological and Biochemical Foundations of Living Systems
AAMC Categories:
3B: Respiratory system structure and function
3C: Immune response, infectious disease
1A/1B: Biochemistry of drug mechanisms
They may include:
Drug MOA (mechanism of action)
Resistance profiles
Acid-fast properties
Granuloma formation
🔬 Breakdown of TB Drug Mechanisms (RIPE)
| Drug | Target | Function |
|---|---|---|
| Rifampin / Rifabutin | RNA Polymerase | Inhibits mRNA synthesis (DNA-dependent) |
| Isoniazid | Mycolic acid synthesis | Disrupts fatty acid synthesis, essential for cell wall |
| Pyrazinamide | Acidic intracellular environment | Active inside macrophages; unclear precise MOA |
| Ethambutol | Arabinogalactan synthesis | Inhibits arabinosyl transferase in the cell wall |
🧠 MCAT Tip: Match drug to location—e.g., Isoniazid works on the cell wall; Rifampin acts on nucleic acid synthesis.
🩺 Drug Summary Table (from the image)
| Bacterium | Prophylaxis | Treatment |
|---|---|---|
| M. tuberculosis | Isoniazid | Rifampin, Isoniazid, Pyrazinamide, Ethambutol (“RIPE” mnemonic) |
🔥 Mnemonic: RIPE for Treatment
R = Rifampin
I = Isoniazid
P = Pyrazinamide
E = Ethambutol
📌 Extra MCAT Nugget: Rifampin turns body fluids orange. Ethambutol causes optic neuritis. Isoniazid is linked with vitamin B6 deficiency.
🚨 High-Yield Clinical Correlations
HIV/TB co-infection: Rifabutin preferred over rifampin to avoid P450 induction
PPD+ (Latent TB): Ison
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