Question

Explain pharmacokinetic interactionsunder ADME. Give an example to each oneand mention the outcome of these interactions. can anyone write long ?

Answer 1

The answer to your query is as follows:

The abbreviation used in pharmacokinetics is ADME. It stands for

A- Absorption

D- Distribution

M- Metabolism

E-Excretion.

In pharmacology the process explains the disposition and kinetics of a pharmaceutical drug or a pharmaceutical compound in the body of an organism.

The process shows the effect of the drug levels and the exposure of the drug to the tissues and cells of the body.

Absorption

It is the process that involves the administration of a pharmaceutical drug to reach a tissue. The drug is taken with the help of the mucous membranes of the digestive tract into the bloodstream.

Various factors affect the extent to which a drug is absorbed through the mucous membranes after oral administration are:

• poor solubility of the compound
• emptying time in the stomach
• transit time in the intestine
• Gastric chemical instability

The absorption helps in determining the bioavailability of the compound.

Poorly absorbed drugs by oral routes should be given intravenously or can also be administered by inhalation. For example, zanamivir.

Changes in gastrointestinal pH, chelation, and gastrointestinal motility are the most important factors that lead to the significant interactions of the drugs.

For example, the changes in gastric pH result in a reduction in the absorption of two important drugs like Ketoconazole and Itraconazole.

Another example is of chelation in which Tetracyclines and ciprofloxacin form insoluble chelates with calcium and iron and thus reduces the antibacterial effects of the.

Another example is the motility changes in the gastrointestinal tract. Drugs like propantheline help in increasing the absorption of Digoxin by 30% which otherwise is slowly dissolved. It is because the reduction in the gut motility gives more time to slow dissolving Digoxin to pass into solution form. Thus, leads to more absorption

Distribution

The compound or the pharmaceutical drug should reach to the effector site with the help of the bloodstream. After absorption, it should distribute into the systemic circulation like muscle and organs.

Factors that affect drug distribution are:

• Blood flow rates at regional levels
• the molecular size of the drug
• the polarity of the drug and its binding to serum proteins

For example, the administration of drugs like warfarin with Phenylbutazone concomitantly increases the levels of warfarin.

Metabolism

The compounds break down into simpler components called metabolites as soon as they are administered in the body. The major site for drug metabolism is the liver in which redox enzymes like cytochrome P450 perform the process of metabolism.

Enzyme induction or activation results in increased metabolism of the drug.

For example, in the drug combination of warfarin and phenobarbital, the phenobarbital increases the metabolic rate of warfarin and thus results in decreased anticoagulant activity.

Excretion

This process helps in the removal of compounds and their toxic metabolites from the body. The main organ involved is kidneys that remove the toxic substances in the form of urine.

Biliary excretion also called fecal excretion starts in the liver and continues through the gut. The waste products are excreted in the form of feces.

Lungs also help in this process by excreting anesthetic gases.

The important mechanisms that involve the interactions of excretion are:

• Changes in the renal blood flow
• Changes in the urine pH
• Forced diuresis

For example, the drug combination that alters the urine pH are antacids with amphetamine.

Outcomes of these drug interactions are as follows:

• Drug interactions can lead to loss of the therapeutic effect of the drug.
• It can lead to toxicity in the body.
• There can be an unexpected rise in the pharmacological activity of the drug.
• The beneficial effects of the drug interactions can be additive as well as potentiating
• There can also be chemical or physical interaction like I.V incompatibility can occur in syringes mixtures

I hope it helps!