Introduction to Pharmacotherapy
Pharmacotherapy is the use of drugs to prevent, treat, or manage disease. It integrates knowledge from basic sciences, clinical medicine, and patient‑centered care to achieve optimal therapeutic outcomes.
1. Core Objectives
| Goal |
What it Means |
| Efficacy |
Select agents that produce the desired therapeutic effect. |
| Safety |
Minimize adverse drug reactions (ADRs) and drug‑drug interactions. |
| Adherence |
Choose regimens that patients can follow consistently. |
| Cost‑effectiveness |
Use therapies that provide value for the health system and the patient. |
| Individualization |
Tailor treatment to age, organ function, genetics, comorbidities, and patient preferences. |
2. Fundamental Concepts
2.1 Pharmacodynamics (PD)
- Mechanism of Action (MoA): How a drug interacts with a biological target (receptor, enzyme, ion channel).
- Dose‑Response Relationship:
- Efficacy – maximal effect a drug can produce.
- Potency – concentration needed to achieve a given effect.
- Therapeutic Index (TI): Ratio of toxic dose to effective dose; a wide TI = safer drug.
2.2 Pharmacokinetics (PK) – “What the body does to the drug”
| Process |
Key Parameters |
Clinical Implications |
| Absorption |
Rate, extent (bioavailability) |
Food effects, formulation choice |
| Distribution |
Volume of distribution (Vd), protein binding |
Tissue penetration, drug‑drug displacement |
| Metabolism |
Phase I (oxidation, reduction), Phase II (conjugation) |
Enzyme inducers/inhibitors, genetic polymorphisms |
| Excretion |
Renal clearance, biliary excretion |
Dose adjustment in renal/hepatic impairment |
3. Drug Classification Overview
| Class |
Typical Indications |
Representative Agents |
Key Safety Points |
| Analgesics |
Pain |
Acetaminophen, NSAIDs, Opioids |
GI bleeding (NSAIDs), respiratory depression (opioids) |
| Antibiotics |
Bacterial infections |
Penicillins, Cephalosporins, Fluoroquinolones |
Allergic cross‑reactivity, C. difficile risk |
| Antihypertensives |
Hypertension, heart failure |
ACE‑I, ARBs, β‑blockers, Calcium channel blockers |
Electrolyte shifts, renal function monitoring |
| Antidiabetics |
Type 2 diabetes |
Metformin, SGLT2‑i, GLP‑1 RAs |
Lactic acidosis (metformin), ketoacidosis (SGLT2‑i) |
| Psychotropics |
Mood, psychosis, anxiety |
SSRIs, SNRIs, Atypical antipsychotics |
Serotonin syndrome, metabolic syndrome |
| Anticoagulants |
Thrombosis prevention |
Warfarin, Direct oral anticoagulants (DOACs) |
Bleeding risk, INR monitoring ( |