Journal of Drug Metabolism & Toxicology
Open Access

The Science of Drug Metabolism: How Our Bodies Break Down Medications

Rhodes Bobrova^{* *}Correspondence: Rhodes Bobrova, Department of Pulmonary Diseases, University of Groningen, Groningen, The Netherlands, Email:

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Introduction

Pharmacokinetics is the study of the Absorption, Distribution, Metabolism, and and Excretion (ADME) of drugs in the body. It is an essential aspect of pharmacology as it helps to understand the effects of drugs on the human body, including the duration of action, toxicity, and drug interactions. In this article, we will discuss the different aspects of pharmacokinetics in detail.

Description

Absorption: Absorption is the process by which drugs enter the bloodstream and become available for use in the body. It can occur through various routes such as oral, intravenous, subcutaneous, intramuscular, and transdermal. Oral absorption is the most common route of administration for drugs, and it involves the drug passing through the gastrointestinal tract before entering the bloodstream. Factors that affect oral absorption include the pH of the gastrointestinal tract, food intake, and the presence of other drugs. Intravenous administration is the fastest route of absorption, and it involves injecting the drug directly into the bloodstream. Subcutaneous and intramuscular administration involves injecting the drug into the tissues beneath the skin or into the muscles, respectively. Transdermal administration involves applying the drug to the skin, and it is commonly used for drugs such as nicotine patches.

Distribution: Once a drug is absorbed into the bloodstream, it is distributed throughout the body. The distribution of drugs is affected by various factors such as blood flow, the concentration of the drug, and the binding of the drug to plasma proteins. Some drugs have a high affinity for plasma proteins, which means they bind to them and are not available for use in the body. Other drugs have a low affinity for plasma proteins, which means they are freely available for use in the body. The distribution of drugs is also affected by the blood-brain barrier, which prevents many drugs from entering the brain.

Metabolism: Metabolism is the process by which drugs are broken down in the body. The majority of drug metabolism occurs in the liver, although other organs such as the kidneys and lungs can also play a role. The primary purpose of drug metabolism is to convert the drug into a more water soluble form so that it can be excreted from the body. The process of drug metabolism can involve various enzymes, including cytochrome P450 enzymes, which are responsible for the metabolism of many drugs. Drug metabolism can also result in the formation of metabolites, which may have different pharmacological properties than the parent drug.

Excretion: Excretion is the process by which drugs are eliminated from the body. The primary route of drug excretion is through the kidneys, although drugs can also be eliminated through the liver, lungs, and gastrointestinal tract. The rate of drug excretion is affected by various factors such as urine pH, renal function, and the rate of drug metabolism.

Pharmacokinetic parameters: Pharmacokinetic parameters are used to describe the ADME of drugs in the body. The most common pharmacokinetic parameters include:

Clearance: Clearance is the rate at which a drug is eliminated from the body. It is measured in units of volume per unit time, such as milliliters per minute.

Volume of distribution: The volume of distribution is the theoretical volume that would be required to contain the entire amount of drug in the body at the same concentration as it is in the plasma. It is calculated as the amount of drug in the body divided by the concentration of the drug in the plasma.

Half-life: The half-life is the time it takes for the concentration of a drug in the plasma to decrease by half. It is a useful parameter for understanding the duration of action of a drug.

Conclusion

PEGylation is an effective approach to potentiate drugs with undesirable properties. Currently, PEGylation has penetrated into every field of pharmaceutical practice, involving bio-macromolecules, small drugs and drug delivery systems. Efficacy enhancement is attained through modification of the pharmacokinetics and toxicity profiles of parent drugs. As a result of PEGylation, the drugs tend to display enhanced solubility, prolonged circulatory time and reduced immunogenicity/antigenicity. The bottleneck of PEGylation is how to break through the limitation of chemical conjugation and to properly preserve the pharmacological activity of the drug. PEGylated formulation is an area deserving more attention in terms of systemic delivery of insoluble small drugs.