Understanding Drug Absorption in Pharmacology

📚 Absorption is the first step in pharmacokinetics, referring to the drug's passage from the site of administration to the bloodstream.

💊 Topical medications are administered directly to the site of action and do not require absorption into the bloodstream.

🩸 Orally administered medications travel through the intestines, liver, heart, lungs, and various tissues in the body via the bloodstream.

🩸 Medications administered through intravenous route bypass the absorption process, leading to faster effects.

🧪 The main challenge in the absorption process is crossing the cell membranes, which can be achieved through passive diffusion, facilitated diffusion, active transport, or endocytosis.

🚀 Passive diffusion is the most common form of transport used by medications, utilizing the concentration gradient without requiring energy.

🧪 Passive diffusion is the easiest way for drugs to cross the cell membrane, as long as they are minimally lipophilic.

🔁 Hydrophilic drugs can also cross the membrane through passive diffusion using concentration gradients and carrier proteins.

⚠️ However, the process of facilitated diffusion is limited by specific binding sites on carrier proteins.

Different forms of active transport, such as diffusion and endocytosis, are involved in the absorption of drugs through membranes.

Factors like liposolubility, molecular weight, and tissue arrangement affect the absorption of drugs.

Barriers like the blood-brain barrier have tight junctions to prevent the passage of certain molecules.

🔑 To pass the blood-brain barrier, a drug needs to be highly lipophilic or small in size.

🔍 The electrical charge of a drug molecule is important, with many drugs being weak acids or weak bases.

🧪 The pH of the environment determines whether a drug is in its ionized or non-ionized form.

🔑 The ability of a drug to be absorbed depends on its ionization and lipid solubility.

🔑 Acidic drugs are more easily absorbed in acidic environments, while basic drugs are better absorbed in alkaline environments.

🔑 The concentration of a drug and its pharmaceutical form also affect absorption, with higher concentrations and liquid forms being absorbed more quickly.

🔑 The area of absorption in the body is an important factor, with larger areas leading to better absorption.

🧠 Absorption of medications in the intestine is influenced by factors such as the large surface area, acidic nature of the drugs, and the presence of electric charge.

⏰ The time of gastric emptying, intestinal motility, and food intake also affect the absorption of drugs, along with the dissolution time of tablets and capsules.

💉 Vascularization plays a crucial role in drug absorption, as more blood vessels increase the chances of drugs entering the bloodstream.

🩺 Various gastrointestinal conditions can impact the absorption of medications, highlighting the importance of considering pathological factors.