Pharmacodynamics

Drug actions:
The cellular processes involved in the drug and cell interaction
Drug effect:
The physiologic reaction of the body to the drug.
Onset:
The time it takes for the drug to elicit a therapeutic response
Peak:
The time it takes for a drug to reach its maximum therapeutic response

Duration:
The time a drug concentration is sufficient to elicit a therapeutic response.
Mechanisms of Action:
The ways by which drugs can produce therapeutic effects:
Once the drug is at the site of action, it can modify the rate (increase or decrease) at which the cells or tissues function. A drug

cannot make a cell or tissue perform a function it was not designed to perform.
Types of Drug interaction in the body;
Specific interaction


Receptor interaction
Enzyme interaction
Non Specific interaction
Plasma proteins. e.g. Albumin and globulin.
Other non functional cell component
Types of Drug Effect
Cure and eradicate: Antibacterial and anti- parasite
Treat: Hypertension, Headache.
Explore: contrast media e.g. Barium sulfate.
Replace: Hormonal supplements
Stimulate: rarely
Inhibit: in all most cases
Inhibition:
Antagonists of Cell Surface Receptors
Antagonists of Nuclear Receptors
Enzyme Inhibitors
Ion Channel Blockers
Transport Inhibitors
Inhibitors of Signal Transduction Proteins
Drugs are usually either weak acids or weak basis.
Drugs should be formulated in form of salts to:



improve their water solubility and other kinetics.
To protect against their aggressive chemical property.
In physiological pH drugs retain their formal chemical properties.
Drugs present outside the body in two forms:
1- Active drug.
2- pro-drug.
Drugs present inside the body in two forms
1- Free drug: Active form
2- Bound drug: In active form
3- Metabolites: Could be active or inactive.
Properties of Specific & Non-specific drug interaction
Specific interaction
Saturable process: because of limited receptor molecules.
Predicted effects.
Measurable drug effects.
Structure Specific
Non-specific interaction
Non saturable process.
Non predicted effects.
Non measurable drug effects.
Non structure Specific.