Search Results
You are looking at 1-10 of 121
![Figure 1.](/view/journals/anpr/58/4/inline-i0003-3006-58-4-166-f01.png)
Pharmacokinetic considerations. The concentration of drug at the target tissue is determined by combined influences of absorption, metabolism, distribution, and elimination (excretion). Notice obstacles to bioavailability (serum concentration) following oral and intramuscular administration compared to those following intravenous administration.
![Figure 5.](/view/journals/anpr/58/4/inline-i0003-3006-58-4-166-f05.png)
Pharmacokinetic compartments. Following an intravenous bolus, drug introduced into the bloodstream (central compartment) distributes into peripheral tissues (peripheral compartment). In the three-compartment model these tissues are divided into those highly perfused (shallow) and less perfused (deep). As the serum concentration declines due to distribution or elimination, drug in the peripheral compartments will equilibrate by redistribution into the central compartment. The time-concentration curve illustrates the decline in serum concentration attributable to rapid distribution into highly perfused tissues, intermediate distribution to less perfused tissues, and a slow decline due to drug elimination.
![Figure 1.](/view/journals/anpr/53/4/inline-i0003-3006-53-4-140-f01.gif)
Drug absorption. Following oral (PO) or topical administration, a drug requires lipid solubility in order to diffuse through the epithelium to reach the capillaries. When administered by intramuscular (IM) or subcutaneous (SC) injection, lipid solubility is not required to reach the capillaries. Once absorbed following PO administration, a drug must travel through the portal system to liver before reaching systemic circulation (venae cavae). See text for further explanation.
![Figure 2.](/view/journals/anpr/53/4/inline-i0003-3006-53-4-140-f02.gif)
Drug distribution. Drug molecules (D) circulate in blood stream unbound and bound to plasma proteins. Only unbound drug is free to distribute into tissues. Systemically, distribution is a simple matter of diffusion through the loosely-joined endothelium of the capillaries. Distribution to the brain requires lipid solubility because the capillary endothelium is tightly bound and wrapped with astrocytes.