Transdermal is not a route of drug administration, but rather a method of drug delivery through the skin.

The rate and extent of drug absorption are influenced by a combination of drug formulation, physicochemical properties of the drug, and the route of administration.

Pinocytosis is a process of cellular uptake involving the engulfment of extracellular material by invagination of the cell membrane, not a mechanism of drug absorption.

The distribution of a drug in the body is affected by protein binding, tissue perfusion, and drug lipophilicity.

Excretion is the process of eliminating drugs and their metabolites from the body, not a mechanism of drug metabolism.

The liver is the primary site of drug metabolism, where enzymes such as cytochrome P450 enzymes play a crucial role in metabolizing drugs.

Pulmonary excretion is not a significant route of drug excretion, as most drugs are eliminated through renal or biliary excretion.

Excretion is the process of eliminating drugs and their metabolites from the body, typically through the kidneys, liver, or intestines.

Drug metabolism can be influenced by factors such as age, genetic variations, and drug interactions.

Bioavailability refers to the fraction of a drug that reaches systemic circulation after administration, taking into account factors like absorption, first-pass metabolism, and bioavailability enhancers.

Drug concentration is not a factor that directly affects drug distribution, as distribution is primarily determined by factors like protein binding, tissue perfusion, and drug lipophilicity.

Phase II metabolism involves the conjugation of drugs with polar molecules, such as glucuronic acid or sulfate, to increase their water solubility and facilitate excretion.

Passive diffusion is not a mechanism of renal drug excretion, as drugs are actively transported or filtered across the renal tubules.

First-pass metabolism occurs when a drug is metabolized before it reaches systemic circulation, typically in the liver or gut wall.