Main Takeaway: A P-drug is a prescriber’s personal choice of first-line medicine for a specific indication, selected through a systematic and evidence-based process. Developing and maintaining a personal formulary of P-drugs streamlines decision-making, promotes rational therapeutics, and enhances patient safety.
1. Definition and Purpose of P-Drugs
A P-drug (“personal drug”) is not merely the generic name of a medicine but encompasses:
- The drug substance itself
- The dosage form (e.g., tablet, injection)
- The dosage schedule (e.g., once daily)
- The duration of treatment
P-drugs serve as a clinician’s priority choices for given indications, reducing repetitive searches in daily practice and ensuring familiarity with each drug’s effects and side effects.
2. Relation to Essential Medicines and Guidelines
- Essential Medicines Lists (EMLs): National or WHO EMLs often contain dozens to hundreds of options; clinicians typically use only 40–60 drugs regularly. By selecting P-drugs from these lists, practitioners effectively create a personal essential medicines list tailored to their practice context.
- Standard Treatment Guidelines (STGs): Evidence-based STGs for common conditions should inform P-drug selection. P-drugs should align with STG recommendations while accounting for local availability, cost, and patient factors.
3. The Six-Step Process for Rational Prescribing
The WHO Guide to Good Prescribing outlines a six-step model, with P-drug selection comprising Step 3:
- Define the patient’s problem. Summarize diagnosis and relevant patient characteristics (e.g., comorbidities, allergies).
- Specify the therapeutic objective. Establish clear, measurable goals (e.g., reduce blood pressure to <140/90 mmHg).
- Choose and verify your P-drug:
a. Select a P-drug for the indication (Step 3a).
b. Verify its suitability for this patient (Step 3b)—check for contraindications, interactions, and patient-specific factors. - Write the prescription. Include drug name, dose, schedule, and duration.
- Provide information to the patient: instructions and warnings.
- Monitor effectiveness and adverse effects; adjust or stop treatment as needed.
4. Criteria for Selecting P-Drugs (The STEP Framework)
When comparing drug options, apply the STEP criteria:
- Safety: Evaluate adverse-effect profiles and contraindications.
- Therapeutic efficacy: Assess evidence of clinical benefit.
- Economy (cost): Consider affordability and cost-effectiveness.
- Propriety (suitability): Account for patient convenience, formulation, dosing schedule, and special conditions (e.g., pregnancy).
Example: Selecting a P-Drug for Acute Amoebic Dysentery
Among nitroimidazoles, tinidazole may be preferred over metronidazole due to similar efficacy and cost but greater suitability (shorter course, once- or twice-daily dosing).
5. Benefits of a P-Drug Formulary
- Efficiency: Reduces time spent reviewing alternatives for routine cases.
- Familiarity: Clinician expertise with P-drugs improves recognition of expected effects and adverse reactions.
- Consistency: Supports standardized prescribing practices within and across healthcare teams.
- Rationality: Mitigates impulsive or non-evidence-based choices influenced by marketing or habit.
By systematically selecting and regularly reviewing P-drugs according to these principles, prescribers establish a robust foundation for safe, effective, and cost-conscious patient care.
