Pharmacokinetics

Pharmacokinetics

Pharmacokinetics role

What the body does to the drug.

Factors affecting drug absorption

Drug administration routes

Plasma concentration

Intravenous advantages

Intravenous Directly administered into the circulation. Bypasses

first-pass metabolism. Bioavailability of 100

Intravenous disadvantages

Infection risk .Expensive .Needs professionals to administer

Intramuscular advantages

Bioavailability <100%

Intramuscular disadvantages

Unpredictable absorption depending on blood

flow. Irritating drugs can be painful like the

penicillin.

Subcutaneous advantages

good for drugs with high first pass metabolism

such as morphine sulphate oral solution.

Subcutaneous disadvantages

Can be painful and cause bruises.

Topical advantages

Local effects, generally lower systemic effects

Topical disadvantages

Can have unwanted systemic effects

Transdermal advantages

Good alternative for drugs with high first pass

metabolism

Transdermal disadvantages

Rates on lipid permeation. Allows generally

smaller molecules unless a carrier is present

Inhalation advantages

Lungs permeable to small molecule drugs. Fast

acting. Bypasses first pass metabolism

Oral advantages

Easy, convenient, effective.

Oral disadvantages

First pass metabolism. Can be affected by

stomach ph.

Rectal advantages

Absorption improved over oral as some of the

veins in the rectum lead directly to general

circulation → bypasses first pass metabolism

(Rang 2016)

Factors affecting drug absorption

Disintegration

Drug from drugs can be administered

Disintegration and dissolution of drugs – GI acidity

and motility

Oral absorption facts

Factors influencing drug absorption

Cell membrane and fat solubility of drugs

Drugs and solubility

Degree of ionisation

Passive vs facillated diffusion

pH and ionisation

Factors influencing drug absorption

Bioavailability

Hepatic 1st Pass Metabolism and oral Bioavailability

Overall Drug Bioavailability if affected by:

Dosage form/route administration/Dissolution of drug

Drug distribution

Drug distribution: Cell membrane Permeation

Diffusion through lipids

Anatomical Barriers for drug distribution via

cell membrane permeation

Blood Brain Barrier

Neonates

Inflammation

Summary of facts affecting distribution

Drug distribution bulk flow

Volume distribution

Drug solubility

Volume distribution

Drug high volume

Drug with low distribution

Drug high distributions

Drugs with low volume disrtribution

Factors afffecting distribution

Phase 1

Phase 2

Drug metabolism phase 1 oxidation

COWPATS

Renal secretion

Glomerular Filtration

Passive reabsorption

processes of renal secretion

Renal secretion

Renal clearance

Drug half life

steady state concentration

First order

Zero order

Pharmacokinetics quiz