Biochemistry and Clinical Pharmacy: Pathways, Dosing and Pharmacovigilance
Biochemistry and Clinical Pharmacy links metabolic pathways, laboratory interpretation and bedside therapeutics: dose adjustment, therapeutic drug monitoring, ADR reporting and patient counselling.
Core rules
- Key pathways: glycolysis, Krebs cycle, oxidative phosphorylation, HMP shunt, gluconeogenesis, urea cycle and β-oxidation; ALT, AST, ALP and CK are organ markers.
- Vitamins and coenzymes: thiamine (TPP), riboflavin (FAD), niacin (NAD), pyridoxine (PLP), biotin (carboxylation), cobalamin and folate (one-carbon transfer).
- Renal adjustment: Cockcroft–Gault creatinine clearance = [(140 − age) × weight kg]/(72 × serum creatinine mg/dL), multiplied by 0.85 for women.
- Therapeutic drug monitoring: digoxin (sample 6–8 hours post-dose at steady state), phenytoin (total and free), lithium (12 hours post-dose), vancomycin (trough) and warfarin (INR).
- Pharmacovigilance: PvPI, ADR reporting form, WHO-UMC and Naranjo causality scales; Type A (dose-related) and Type B (idiosyncratic) reactions.
Worked example
A 60-year-old woman weighing 60 kg has serum creatinine 1.2 mg/dL. CrCl = [(140 − 60) × 60]/(72 × 1.2) × 0.85 = (4800/86.4) × 0.85 = 55.6 × 0.85 = 47.2 mL/min. A renally cleared drug requiring dose reduction below 50 mL/min should therefore be adjusted.
Traps
Do not calculate CrCl without the female factor; do not sample digoxin soon after a dose; do not adjust a hepatically cleared drug on creatinine alone; and do not report an ADR without the suspected drug, dose, timeline and outcome.