Where medications are excreted and metabolized

Medication metabolism is the biotransformation of pharmaceutical substances in the body to enable easy elimination. It is usually an enzymatic process. Medication drug excretion is the elimination of the intact drug. Drugs are mainly excreted through renal excretion (drug travels from the kidney to bladder and then to urine). Other means are sweat, bile, saliva, and other body fluids. All drugs are eliminated from the body, and the liver is the principal organ of metabolism. At the same time, the kidney is responsible for excretion. 

Medication metabolism

Although many sites are involved in metabolism, the liver is the top site for metabolism. Most drugs must pass through the liver, where enzymes convert prodrugs to active metabolites. Drug metabolism goes through two phases, Phase 1, and Phase 2.

The first phase involves forming a new or modified functional group. In contrast, the second phase reaction involves conjugation with an endogenous substance. On some occasions, drugs only undergo the first phase or only the second phase. In contrast, the drug will often undergo the first and second phases.

Drugs can be metabolized by

  • Oxidation
  • Hydration
  • Reduction
  • Condensation
  • Hydrolysis

All these processes are aimed at making the drug easier for the excretion process

Medication excretion

The excretion of most drugs and their metabolites are eliminated primarily by the kidneys in urine. Excreted drugs are either eliminated in their unmetabolized form or eliminated through biotransformation. Some drugs pass through metabolism before being excreted, while others are excreted in their original form.

Some drugs can be excreted in the

  • Saliva
  • Sweat
  • Faces
  • Breast milk and exhalation from the lungs

Renal excretion is the most common means through which drugs are eliminated. However, the rate at which drugs are excreted from the kidney may be affected by a few factors: Kidney disease, pH of urine, change in renal blood flow, and molecular weight.