Journal of Bioequivalence & Bioavailability

Comprehensive Assessment and Contemporary Practice of Drug Absorption in Pharmaceutical Industry

Kirsten Alycia^* Department of Pharmacy, The University of Queensland, Brisbane, Australia
^*Correspondence: Kirsten Alycia, Department of Pharmacy, The University of Queensland, Brisbane, Australia, Email:

Received: 24-Mar-2023, Manuscript No. JBB-23-21369; Editor assigned: 30-Mar-2023, Pre QC No. JBB-23-21369 (PQ); Reviewed: 13-Apr-2023, QC No. JBB-23-21369; Revised: 20-Apr-2023, Manuscript No. JBB-23-21369 (R); Published: 27-Apr-2023, DOI: 10.35248/0975-0851.23.15.516

Description

Drug absorption is a complex and essential process that determines the bioavailability of drugs in the body. Bioavailability refers to the fraction of a drug that reaches systemic circulation after administration and is available to exert its therapeutic effect. The absorption of drugs can occur through various routes, including oral, transdermal, intravenous, and inhalation. However, the efficacy of drug therapy largely depends on the extent and rate of drug absorption, which can be affected by several factors. Oral drug absorption is the most common route of drug administration, and it involves the uptake of drugs through the gastrointestinal tract. However, the absorption of orally administered drugs is influenced by various factors such as the solubility of the drug, the pH of the stomach and intestine, and the presence of food in the stomach. For instance, drugs that are poorly soluble in water or have low permeability across the gastrointestinal wall may have limited bioavailability. Similarly, acidic drugs are better absorbed in the acidic environment of the stomach, while alkaline drugs are better absorbed in the basic environment of the small intestine.

Another critical factor that affects oral drug absorption is food. Food can alter the absorption rate and extent of drugs by affecting the gastric emptying rate, pH, and motility of the gastrointestinal tract. For example, food can delay the absorption of drugs by reducing the gastric emptying rate or by altering the pH of the stomach. On the other hand, some drugs may require food to enhance their absorption. Therefore, it is essential to take drugs as prescribed, with or without food, to ensure optimal absorption and efficacy. Intravenous drug administration involves the direct injection of drugs into the bloodstream. This route of administration provides rapid and complete drug absorption, with bioavailability approaching 100%. However, intravenous administration has its limitations, including the need for trained personnel to administer the drug and the risk of infection at the injection site. Additionally, intravenous administration may not be suitable for drugs that are not compatible with the bloodstream or for drugs that require prolonged administration.

Transdermal drug delivery involves the absorption of drugs through the skin. This route of administration has gained popularity due to its non-invasive nature, ease of use, and prolonged drug delivery. However, transdermal drug absorption is limited by the skin's barrier function, which restricts the entry of hydrophilic and large molecules. Therefore, drugs that are lipophilic and have low molecular weight are better suited for transdermal delivery. Inhalation is another route of drug administration that involves the absorption of drugs through the lungs. This route of administration provides rapid drug absorption, with high bioavailability. Inhalation is commonly used for drugs that act locally in the lungs, such as bronchodilators for asthma. However, inhalation has its limitations, including the risk of lung irritation and the potential for drug accumulation in the lungs.

Drug absorption can also be affected by the physicochemical properties of drugs, such as solubility, permeability, and lipophilicity. For instance, drugs that are highly soluble and permeable are more likely to have high bioavailability. Similarly, lipophilic drugs can readily cross biological membranes, leading to faster and more extensive absorption. However, drugs that are highly lipophilic may accumulate in fatty tissues, leading to prolonged effects or toxicity. The dosage form and formulation of drugs also play a crucial role in drug absorption. The dosage form refers to the physical form of the drug, such as tablets, capsules, or solutions, while the formulation refers to the composition of the drug product, such as excipients and additives. The dosage form and formulation can affect drug dissolution and solubility, which in turn affect drug absorption.

On the other hand, drugs that are administered intravenously bypass the first-pass metabolism and are directly delivered to the systemic circulation, resulting in higher bioavailability. Other routes of administration such as intramuscular, subcutaneous, transdermal, and inhalation also have different absorption profiles.

Some drugs are better absorbed in the presence of food, while others are better absorbed in the fasting state. The motility of the gastrointestinal tract can also affect drug absorption. Drugs that are poorly absorbed in the stomach may need to be administered with a prokinetic agent to enhance their absorption. The surface area of the gastrointestinal tract also influences drug absorption. The small intestine has a larger surface area than the stomach, which allows for more efficient absorption of drugs. The patient's health status also influences the drug absorption. Various medical conditions can affect gastrointestinal physiology and, consequently, drug absorption. For instance, patients with inflammatory bowel disease may have impaired absorption due to inflammation and damage to the intestinal mucosa. Patients with liver or kidney disease may have altered drug metabolism and excretion, which can affect drug absorption. Elderly patients may have decreased gastrointestinal motility, which can affect drug absorption. Therefore, it is essential to consider the patient's health status when selecting a route of administration and dosing regimen.