Materia Medica and Herbal Pharmacology
What to master
Materia medica questions test identification, part used, active constituents, actions, dose forms, and safety. For each important herb know: botanical and common name, the part used (leaf, root, seed, bark), the main active chemical groups (alkaloids, glycosides, tannins, volatile oils, saponins, mucilage), the principal action, typical preparation, and known contraindications. Understand that pharmacology of herbs follows the same principles as conventional drugs: dose–response, absorption, metabolism, and interaction.
Key concepts
- Active constituents: alkaloids (often potent, sometimes toxic), cardiac glycosides (narrow therapeutic index), tannins (astringent), volatile oils (antimicrobial, irritant), mucilage (demulcent).
- Herb–drug interactions: anticoagulant interactions, effects on liver enzymes, and additive sedation or blood-pressure effects.
- Toxicity and dose: many herbs are safe at therapeutic dose but toxic in excess; some are contraindicated in pregnancy.
- Adulteration and substitution: a major safety issue in traditional markets.
Traps
- Assuming 'herbal' means 'safe at any dose'.
- Confusing the part of the plant used - the same plant can have different actions in leaf versus root.
- Ignoring cumulative or additive effects with conventional medicines.
Rule of thumb
For any herb question, run the P-A-C-E check: Part used, Active constituent, Contraindication, Evidence of interaction. If you can name all four, you can usually eliminate wrong options.
Worked example: A patient on warfarin asks about a herbal preparation. The P-A-C-E check flags a potential interaction (anticoagulant effect), so the correct answer is to advise against unsupervised use and refer - not simply to reassure.