The absorption of drugs in the human body refers to the process of the drug’s movement to the bloodstream. Depending on the administration route of the drug, the drug can be absorbed in different methods; therefore, drug concentrations are formulated differently depending on the administration method. Injections do not require absorption; however, all other drug formulas require being in solution form to be absorbed. In oral administration, the drug is absorbed through epithelial cells of the gastrointestinal tract.
The distribution of the drug is especially important because it determines the drug’s effect on the body. The drug is delivered to different tissues within the body through the bloodstream. Thus, depending on individual characteristics such as blood perfusion, the distribution process can take less or more time in different patients. Furthermore, the process of the drug’s distribution can be longer in tissues with high affinities, such as muscles, or in tissues with membrane barriers, such as the brain. Drug distribution knowledge is vital for understanding the drug’s effect on the body, including its benefits and toxicity. For example, in pregnant women, certain drugs can be transferred through the placenta, but other drugs can accumulate in the placenta, affecting fetal development (Tetro et al., 2018). Thus, understanding the drug pharmacokinetics is essential for maintaining the individual’s health.
Lastly, the elimination of drugs from the human body involves the metabolism process and excretion. Metabolism refers to the individual characteristics defining the effectiveness in the work of Cytochrome P450 enzymes. Next, the excretion of the drug presents a process involving a series of ways of removal of the drug through the kidneys. Therefore, the most common form of drug elimination is through urine. Other less common ways of drug excretion from the body include sweat, saliva, and stool.
Reference
Tetro, N., Moushaev, S., Rubinchik-Stern, M., & Eyal, S. (2018). The placental barrier: the gate and the fate in drug distribution. Pharmaceutical Research, 17, 1-16.