PT
● MODULE 20 / 20
Local Drugs, Toxicology & Practical Therapeutics
Bring skin, eye and antiseptic drugs together with antidote reasoning, prescriptions and practical revision.
Quick revision ↓ Medical Dictionary
FULL CHAPTER EXPLANATION
Deep Learning — Module 20
Read this section in sequence. It moves from drug targets to therapeutic effects, adverse reactions and safe use.
01
Skin and locally acting medicines
Emollients support barrier hydration; topical corticosteroids suppress inflammation but potency, site, duration and skin condition determine absorption and harm. Prolonged inappropriate use can cause atrophy and systemic exposure. Benzoyl peroxide has acne activity and can irritate skin or bleach fabric; topical retinoids alter keratinization and require product-specific reproductive precautions. Antifungal anti-seborrhoeic products can help selected scalp disorders. Enzymatic debriding agents remove devitalized tissue in defined wound-care settings and do not replace assessment of perfusion or infection.
02
Eye drugs and antisepsis
Glaucoma medicines reduce aqueous production or increase outflow: timolol blocks beta receptors, carbonic-anhydrase inhibitors reduce production, and prostaglandin analogues increase outflow. Ocular beta blockers can still cause systemic bradycardia or bronchospasm. Cataract does not have a generally established medicine that reliably reverses lens opacity; surgery remains the definitive treatment when indicated, with drugs serving perioperative roles. Antiseptics are used on living tissue, while disinfectants are used on inanimate surfaces. Concentration, contact time and material compatibility determine effective use.
03
Poisoning priorities and antidotes
Begin with stabilization, exposure identification and urgent expert assessment. Naloxone antagonizes opioids; acetylcysteine supports detoxification in paracetamol poisoning; atropine treats muscarinic organophosphate effects; selected chelators bind particular metals. An antidote does not replace airway support, circulation assessment or monitoring. Activated charcoal is useful only for selected substances and time windows and can harm an unprotected airway. Emesis is not a routine home poisoning treatment. Exact decisions require poison-service or emergency protocols.
04
Prescription and calculation station
A practical prescription should identify the patient, date, generic medicine, formulation, strength, dose, route, frequency, duration and prescriber, with clear counseling and review. In a hypothetical exercise, a 20 kg patient receiving 5 mg/kg per dose requires 100 mg per dose; if the liquid is 20 mg/mL, that is 5 mL. Distinguish per-dose from per-day instructions before calculating frequency. Check formulation suitability and maximum limits against a current authoritative reference before clinical use.
05
Integrated review and professor check
For any drug, explain target, physiological effect, useful indication, major harm, contraindication or precaution, interaction and monitoring. For a case, first decide the therapeutic objective, then compare alternatives and describe what would make you change course. Practice interpreting a concentration-time curve, a dose-response shift, an adverse-reaction history and a prescription error. These notes and self-assessments support undergraduate revision; faculty review and institutional practical teaching remain essential, and quiz results are learning feedback rather than certification.
High-Yield Revision
- The route can be local while the adverse effect is systemic.
- Match antidote choice to the toxin while stabilizing the patient.
- Carry units and distinguish mg/kg/day from mg/kg/dose.
Common Exam & Concept Pitfalls
- Do not claim eye drops reverse established cataract.
- Charcoal and induced vomiting are not universal poisoning treatments.
Sources & Further Reading
Curriculum scope checked 23 September 2026. These original study notes summarize established principles; current institutional guidance and product information govern clinical use. Faculty review is pending.
RAHBAR study structure: target → drug action → therapeutic use → adverse effects → monitoring. Use institutional curriculum and faculty guidance for local sequencing, practical requirements and assessment specifications.