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P-Drug Selection — Typhoid Fever

Pharmacology Practical Exam Guide

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PART 1: The P-Drug Concept (WHO Framework)

WHO 6-Step Rational Prescribing Model

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PART 2: P-Drug Selection Criteria (ESCS)

Each criterion is given a weight (0–1) depending on its importance for that disease. The four weights must add up to 1. Multiply weight × score for each criterion, then sum = Total Score. The drug with the highest total score becomes your P-drug.

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PART 3: Drug Groups Available for Typhoid Fever

Group A — Fluoroquinolones

• Ciprofloxacin, Ofloxacin, Levofloxacin

Group B — Third-Generation Cephalosporins

• Ceftriaxone, Cefixime

Group C — Azalide/Macrolide

• Azithromycin

Group D — Older Agents (now less preferred due to resistance)

• Chloramphenicol, Ampicillin, Co-trimoxazole (TMP-SMX)

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PART 4: P-Drug Comparison Table for Typhoid Fever

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PART 5: YOUR P-DRUG for Typhoid Fever

P-Drug: Azithromycin (for uncomplicated typhoid in outpatient settings)

Azithromycin  500 mg  orally  once daily  ×  7 days
(Children: 10–20 mg/kg/day, max 1 g/day)

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Alternate P-Drug: Ciprofloxacin (if susceptible strains in your region)

Ciprofloxacin  500 mg  orally  twice daily (BD)  ×  7–14 days
OR
Ciprofloxacin  400 mg  IV  every 12 hours  (until oral route possible)

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Severe/Complicated Typhoid → Ceftriaxone

Ceftriaxone  2 g  IV/IM  once or twice daily  ×  7–14 days
(Children: 75 mg/kg/day)

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PART 6: Quick Summary Table

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PART 7: Key Points for Viva Voce

1. Why not chloramphenicol? High resistance, bone marrow suppression (aplastic anemia), grey baby syndrome.
2. Why azithromycin over ciprofloxacin in MDR? MDR strains are resistant to fluoroquinolones; azithromycin retains activity and is given orally.
3. Defervescence time: Fluoroquinolones → 3–5 days; Cephalosporins → may take longer.
4. Relapse rate: ~10% with chloramphenicol; <5% with fluoroquinolones/ceftriaxone.
5. Chronic carrier treatment: Ciprofloxacin 750 mg BD × 4 weeks (or 28 days).
6. Steroids in typhoid? Dexamethasone is used in severe typhoid with altered consciousness or shock (not routine).
7. P-drug vs. drug of choice: A P-drug is your evidence-based first choice; the drug of choice is the current guideline recommendation — they should match if your selection is rational.

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P-Drug Selection — Acute Pulmonary Edema (Left-Sided CHF)

Pharmacology Practical Exam Guide

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PART 1: Understanding the Condition

Pathophysiology (for viva)

↓ LV function → ↑ LVEDP → ↑ LA pressure → ↑ Pulmonary capillary pressure
                                                        ↓
                              Fluid leaks into interstitium → Alveoli → Hypoxia

Therapeutic Objectives (WHO Step 2)

1. Improve oxygenation
2. Reduce preload (venous return to heart)
3. Reduce afterload (systemic vascular resistance)
4. Promote diuresis (remove excess fluid)
5. Improve cardiac contractility (if needed)

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PART 2: Drug Groups Available

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PART 3: P-Drug Comparison Table

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PART 4: P-Drug Selection — ESCS Scoring

P-Drug 1: Furosemide (Frusemide) — for Preload Reduction / Decongestion

Furosemide  40–80 mg  IV slow injection  STAT
(Repeat dose or increase up to 200 mg if needed)
(Children: 1 mg/kg IV)

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P-Drug 2: Nitroglycerin (GTN) — for Vasodilation / Afterload & Preload Reduction

Nitroglycerin  0.4–0.8 mg  sublingually  STAT  (repeat every 5 min × 3 if needed)
OR
Nitroglycerin  10–20 mcg/min  IV infusion  (titrate upward by 5–10 mcg/min every 5 min)

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PART 5: The Classic Emergency Regimen — "LMNOP"

⚠️ Important note on Morphine (exam viva point): Morphine is traditionally listed but its use is now controversial. Data from the ADHERE registry showed morphine is associated with higher mortality, more ICU admissions, and need for mechanical ventilation. Current AHA guidelines do not recommend routine morphine use. ESC guidelines allow it cautiously. For your P-drug exam, you can list it but must note it is not first-line and carries risks.

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PART 6: Complete Drug List with Doses

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PART 7: Summary — Drug of Choice

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PART 8: Key Viva Points

1. Why furosemide first? It acts within minutes by causing venodilation BEFORE diuresis begins — this immediate preload reduction is the acute benefit.
2. Furosemide dose in CHF patients already on oral furosemide? Give IV dose equal to their total daily oral dose as a single IV bolus (since IV bioavailability ≈ 100% vs oral ~50%).
3. Why prefer torsemide over furosemide in chronic HF? Better and more predictable oral bioavailability; longer half-life.
4. Why not give ACE inhibitors acutely? Risk of precipitous hypotension; used in chronic management, not acute APE.
5. CPAP vs BiPAP? Both effective; BiPAP preferred in patients with respiratory acidosis or CO₂ retention.
6. What is the role of sitting position? Legs dangling → venous pooling → ↓ venous return → ↓ preload → ↓ pulmonary congestion.
7. Morphine in exam vs clinical practice: In exams/textbooks, morphine is classically included in LMNOP. In clinical practice, it is avoided due to evidence of harm (ADHERE registry data).
8. Contraindication to nitrates? Hypotension (SBP < 90 mmHg), right ventricular infarction, use of phosphodiesterase-5 inhibitors (sildenafil).

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P-Drug Selection — Hypertension in Pregnancy (Preeclampsia)

Pharmacology Practical Exam Guide

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PART 1: Understanding the Condition

Definitions (ACOG Classification)

Therapeutic Objectives (WHO Step 2)

1. Prevent maternal hypertensive crises (stroke, placental abruption)
2. Maintain uteroplacental blood flow (protect fetus)
3. Prevent eclamptic seizures
4. Achieve safe delivery

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PART 2: BP Targets in Pregnancy

⚠️ Do NOT lower BP too aggressively — uteroplacental perfusion depends on maternal BP. Aim for controlled, gradual reduction.

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PART 3: Drug Groups Available

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PART 4: P-Drug Selection — ESCS Scoring

Scenario A: Chronic/Mild-Moderate Hypertension in Pregnancy (Oral Therapy)

P-Drug: Methyldopa

Methyldopa  250 mg  orally  twice or thrice daily
(Dose range: 500–3000 mg/day in 2–4 divided doses)

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Alternate P-Drug: Labetalol (preferred by NICE guidelines)

Labetalol  100–200 mg  orally  twice daily
(Range: 200–2400 mg/day)

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Scenario B: Acute Severe Hypertension (SBP ≥ 160 or DBP ≥ 110) — Emergency

P-Drug: Labetalol IV or Nifedipine oral

Nifedipine is the only oral option in acute severe hypertension (when IV access is unavailable). Use immediate-release for emergency; sustained-release for chronic management.

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PART 5: Complete Drug List for Preeclampsia

Antihypertensives

Anti-seizure / Neuroprotective

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PART 6: Summary — Drug of Choice

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PART 7: P-Drug for Your Exam

Tab. Methyldopa  250 mg  orally  thrice daily (TDS)
Duration: Until delivery and 6 weeks postpartum

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PART 8: Absolutely Contraindicated Drugs (Exam Favourite!)

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PART 9: Key Viva Points

1. Why is methyldopa the DOC in India? Longest safety record (40+ years), cheap, no teratogenicity, followed up in children to age 7 with no adverse developmental effects.
2. Why not atenolol in pregnancy? Fetal growth restriction. Other beta-blockers (labetalol, metoprolol) are acceptable.
3. Why is delivery the definitive treatment? Preeclampsia is caused by abnormal placentation — the only cure is removing the placenta.
4. Magnesium sulfate mechanism: Antagonises NMDA receptors in the brain → prevents seizures; also a cerebral vasodilator.
5. How do you monitor MgSO₄ toxicity? Check deep tendon reflexes (first sign of toxicity = loss of patellar reflex at Mg 7–10 mEq/L), respiratory rate (>12/min), and urine output (>25 mL/hour). Antidote = Calcium gluconate 1 g IV.
6. Why avoid ACE inhibitors/ARBs? They reduce angiotensin II → reduced fetal renal perfusion → renal tubular dysgenesis → oligohydramnios → limb contractures, pulmonary hypoplasia.
7. Nifedipine slow release vs immediate release: Slow-release preferred chronically (stable BP). Immediate-release used only in acute severe hypertension.
8. Low-dose aspirin (75–150 mg/day): Given from 12–14 weeks in high-risk women to prevent preeclampsia by inhibiting TXA₂ (thromboxane A₂ production in platelets) while sparing prostacyclin.

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