Question

Explain pharmacokinetic interactionsunder ADME. Give an example to each one and mention the outcome of these interactions. Please write me long :) thanks you.

Answer 1

Pharmacokinetics involves ADME (absorption, distribution, metabolism, and excretion). All of these are connected with both treatment toxicity or failure. It explains the distribution of a pharmaceutical compound within an organism. All these four criteria influence the kinetics and levels of drug exposure to the various tissues and thus influence the overall pharmacological and performance activity of the compound as a drug.

Absorption- A compound is taken into the bloodstream before reaching the target tissue or cell. The factors like gastric emptying time, stomach's chemical instability, solubility, incapacity to penetrate the intestinal wall, and intestinal transit time can all reduce the extent to which a drug is absorbed after oral administration. Absorption crucially circumscribes the bioavailability of a compound. Drugs like zanamivir that are absorbed poorly on oral consumption should be administered intravenously or by inhalation.

Distribution- The compound is distributed to its effector site (muscle and organs) via the bloodstream. The drug is subjected to various distribution processes that result in the lowering of its plasma concentration after entering into the systemic circulation.

The reversible transfer of a drug between two different compartments is known as distribution. The factors that affect the process of drug distribution are molecular size, rates of the regional blood flow, binding of the drug to serum proteins, and polarity. Distribution can be a severe problem at a few natural barriers such as the blood-brain barrier.

Metabolism- The compounds start to break after entering the body. The bulk of small-molecule drug metabolism takes place in the liver by redox enzymes known as cytochrome P450 enzymes. The parent compound forms metabolites when metabolism occurs. The administered dose of the parent drug is deactivated by the metabolism which generally reduces the effects on the body, when metabolites are pharmacologically inert.

Excretion- The compounds and their metabolites are eliminated from the body by the process of excretion. Normal metabolism can be adversely affected if foreign substances get accumulated and are not excreted.

The three major sites for drug excretion are:-

• Kidney- The primary site of excretion. The products are excreted in the form of urine. The three major mechanisms of drug excretion by the kidney are- Active secretion of a drug by transporters (anions- penicillin, urate, etc. and cations- choline, histamine, etc.), Glomerular filtration of unbound drug, passive diffusion (filtrate 100-fold concentrated in tubules for a favorable concentration or biochemical gradient).
• Liver- This type of excretion is called biliary excretion or fecal excretion. The process is initiated in the liver and then the compounds pass through to the gut and are excreted along with waste products or feces.
• Lungs- The anesthetic gases are excreted through the lungs.