loading dose takes volume of distribution into account while maintenance dose takes clearance into account. Because clearance is altered in renal and liver disease, maintenance dose must be decreased in these patients, but loading dose is unaffected.

Zero-Order Elimination

Halflife has no meaning with 0-order (t1/2 is variable)

Zero PEAs for me (high dose phenytoin, ethanolol, high dose aspirin)

First-Order Elimination

typical enzyme kinetics; t1/2 is a constant