Biochemistry and Clinical Pharmacy: Metabolism, Laboratory Data and TDM
Biochemistry and Clinical Pharmacy in GPAT links metabolic pathways, enzyme kinetics, clinical laboratory values and therapeutic drug monitoring. The clinical items reward unit awareness and patient-specific adjustment.
Core biochemistry
- Glycolysis yields net 2 ATP and 2 NADH per glucose; the TCA cycle and oxidative phosphorylation bring the total to about 30–32 ATP.
- CYP450 enzymes mediate phase I oxidation; conjugation (glucuronidation, sulfation, acetylation) is phase II.
- Enzyme inhibitors: competitive raises Km without changing Vmax; non-competitive lowers Vmax.
Clinical pharmacy
- Creatinine clearance estimates renal function for dose adjustment.
- TDM is useful for drugs with narrow therapeutic index (e.g., digoxin, lithium, phenytoin, aminoglycosides); trough sampling is usual for vancomycin.
Worked example
Cockcroft–Gault for a 70-year-old man, 70 kg, serum creatinine 1.4 mg/dL: CrCl = [(140 − 70) × 70]/(72 × 1.4) = 4,900/100.8 = 48.6 mL/min. For a female patient, multiply by 0.85. This value guides renally cleared drug dosing; it is an estimate, not a measured GFR.
Traps
Entering creatinine in µmol/L without conversion; applying the female factor to men; using total body weight in obesity without adjustment; interpreting liver enzymes as quantitative liver function.