How a drug or medicine works in our body (Pharmacokinetics)

by Soumadip Ghosh
Posted: Jun 06, 2020

How a drug or medicine works in our body

Pharmacological action are two types of pharmacokinetics and pharmacodynamics. pharmacokinetics means what body do with drug and pharmacodynamics mean what drug do with the body.

in this section, we discuss about pharmacokinetics. its and non-specific general process. in pharmacokinetics, we can know what body do with drug and this process is continuous with the ADME process.

ADME is absorption, distribution, metabolism, elimination.

Bioavailability:-How much of a drug reaches our blood from the stomach or intestine is called bioavailability.if we take 500 mg paracetamol then reaches 400mg in our blood and 100mg absorbed in the liver.so 400mg is the bioavailability of this drug.

First pass metabolism:-in first-pass metabolism drugs are absorbed in the liver from the stomach or intestine then it absorbs in blood.so, in this case, the metabolism occurs fastly in the liver and when we take 500 mg of paracetamol 200 mg is absorbed in the liver and then it distributed in blood.

Adsorption:-

it is the process of the moment of drug into the systemic circulation from the stomach and intestine. it occurs in four process there are 1. passive 2. active 3. facilitated 4. Pinocytosis*passive process depends on the osmosis process* osmosis is the moment of drug substance of food particles from high concentration to low concentration across the semipermeable membrane.* active process works as opposed to concentration gradient networks low concentration to high concentration so when any substance is going to low concentration to high concentration is required energy.* facilitated is one type of career which are bind with drug and help to cross the membrane.* in the cell membrane small holes are present through this holes some molecule are passing into the cell its called pinocytosis

factor affecting drug absorption:-

Physicochemical properties of drug

Physiological factor

Nature of doses form

Route of drug administration

Bioavailability

1.Physicochemical properties of drug

A. Particle size:- The absorption of the drug is inversely proportional to the particle size and as well as the particle size of drug increase the rate of absorption is decreased and when particle size decreases the rate of absorption is increased. B. Nature of powder form of drug:-The nature of any powder is two types. a) Amorphous b) Crystalline?amorphous powder dissolves very slowly or easily because it takes less energy.?in the crystalline form they require high energy for dissolve solution because they have crystal lattices structure.So, the rate of absorption is high for amorphous powder and the rate of absorption is low for crystalline powder.

C. Solubility or Dissolution:- Rate of absorption of any drug is also depend on the solubility factor. because our gastric media is hydrophilic in nature, so hydrophilic drugs more easily can dissolve it to the gastric HCL, than lipophilic drugs. so the rate of absorption is high for the hydrophilic drug and the rate of absorption is low for the lipophilic drug. D. Salt form of drug:- Strong acid and strong basic drug can easily be dissociated to the solvent, so there dissolution rate for the absorption rate is high. but in case of a weak acid or weak basic drug, their dissociation rate is slow so their absorption is slow. but when we convert the weak acid or weak basic drug into salt form then their rate of dissociation increases many times and the rate of absorption increases.

E. Ionization rate:-Those drug Which are ionic form they can dissolve easily but cannot cross a cell membrane. But in the case of non-ionic form drugs, they can not associate easily, but they are the rate of absorption is high. so we make a drug in such a way we for added time of dissolution they in ionic form and at time of absorption they are ionic form.

How a drug or medicine works in our body (Pharmacokinetics)