1050 ml urine is colected from a patient

concentration of creatinine in urine is 1.8 mg/ml

plasma creatine concentration is 15 mg/L

What is the creatine clearance?

Cl_R = (excretion rate)/(plasma concentration)

(1.05L*1800mg/ml)/(15 mg/ml) = 5.25 L/h

Solubility: Griseofulvin ( ↓ F with ↑ dose)

Saturable transport: Amox, riboflavin ( ↓ Cmax and AUC with ↑ dose due to ↑ F.  Tmax doesnt change)

GI absorption: changes in interstinal bloodflow

Saturable protein binding: Naproxen, cefazolin, salicylates.  ( ↑ Vd with ↑ dose)

Saturable tissue binding: methotrexate ( ↓ Vd with ↑ dose)

Non linearity in metabolism

Hepatic clearance

Saturable metabolism: theophylin, phenytoin

Autoinduction of carbamazepine metabolism

Non linearity in Excretion

Renal clearance

secretion competition between penicillin and probenecid

Tubular reabsorption of ascorbic acid

Nephrotoxicity: Gentamicin alters its own renal excretion

• Saturable hepatic first pass effect
• ↑ dose results in disproportionate ↑ plasma level
• F increses with increasing dose

• Saturable metabolism
• CL ↓ with ↑ dose