Down the hatch: is prescribing medication really that simple?

Area of Science:

• Pharmacology
• Gastroenterology
• Drug Metabolism

Background:

• Drug absorption and metabolism are complex processes influenced by numerous physiological and external factors.
• The gastrointestinal (GI) tract plays a critical role in drug absorption, with the small intestine being the primary site.
• First-pass hepatic metabolism significantly impacts drug bioavailability, especially for orally administered medications.

Purpose of the Study:

• To elucidate the multifaceted factors affecting drug absorption and metabolism.
• To highlight the impact of GI integrity and surgical history on oral drug bioavailability.
• To compare the pharmacokinetic profiles of drugs administered via different routes, considering first-pass metabolism.

Main Methods:

• Literature review of factors influencing drug absorption and metabolism.
• Analysis of pharmacokinetic principles related to GI absorption and hepatic first-pass metabolism.
• Comparison of drug bioavailability across oral and non-oral administration routes.

Main Results:

• Age, sex, pharmacogenetics, comorbidities, drug interactions, formulation, and route of administration significantly alter drug absorption and metabolism.
• GI conditions such as malabsorption syndromes, prior GI surgery (e.g., gastric bypass), and reduced GI blood flow can impair or delay oral drug absorption.
• Non-oral routes bypass hepatic first-pass metabolism, generally resulting in higher bioavailability and drug concentrations compared to oral administration.

Conclusions:

• Effective drug therapy requires consideration of individual patient factors and drug properties that influence absorption and metabolism.
• Gastrointestinal integrity and surgical history are critical determinants of oral drug efficacy.
• Route of administration is a crucial variable affecting drug bioavailability, particularly for drugs subject to extensive first-pass metabolism.