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Many factors can affect the blood flow and delivery of medication, such as decreased blood flow (due to dehydration), blocked vessels (due to atherosclerosis), constricted vessels (due to uncontrolled hypertension), or weakened pumping by the heart muscle (due to heart failure).
Pharmacokinetics of a drug depends on patient-related factors as well as on the drug’s chemical properties. Some patient-related factors (eg, renal function, genetic makeup, sex, age) can be used to predict the pharmacokinetic parameters in populations.
In the simplest sense, the distribution may be influenced by two main factors: diffusion and convection. These factors may be influenced by the polarity, size, or binding abilities of the drug, the fluid status of the patient (hydration and protein concentrations), or the body habitus of the individual.
Different factors can affect drug absorption; these factors can be classified as drug-specific and patient-specific. The percentage of drug absorption varies among different routes of administration, such as oral, subcutaneous (SQ), transdermal, intravenous (IV), and intramuscular (IM).
Pharmacokinetics (PK) is cited as a science dedicated to the study of rate processes such as absorption, distribution, metabolism, and excretion of a drug and the multiple interrelationships affecting same, such as incomplete absorption, saturability in transport, biotransformation, or binding.
Many physiologic differences between children and adults may result in age-related changes in pharmacokinetics and pharmacodynamics. Factors such as gastric pH and emptying time, intestinal transit time, immaturity of secretion and activity of bile ...
Genetic factors contribute to the variability in pharmacokinetics and, in particular, they affect the enzymes and transporters involved in the absorption, distribution, metabolism, and elimination of drugs. This chapter will outline the basic principles of pharmacokinetics as they apply to the disposition of drugs in humans.