Pharmacodynamics.pharmacology slideshare.pptx

Pharmacodynamics

1. Pharmacodynamics Dr Fahad

2. Pharmacodynamics Pharmacon :drug Dynamics :power It is the study of drugs ; what the drug does to the body i.e ; their mechanism of action, pharmacological effect & adverse effects.

3. Types of drug actions Stimulation Depression Irritation Replacement Chemotherapy

4. Stimulation : some drugs activate specialized cells and produce activity, like catecholamines stimulate the heart cells and increase its force of contraction & heart rate . Depression : some drugs act by decreasing the activity of specialized cells, e.g , alcohol depress the CNS. Irritation : some drugs upon application to the skin cause irritaion . By such action they produce local effects .

5. Replacement : in case of deficiency of endogenous substances, drugs can be given to replace the deficiency e.g , insulin in case of diabetes mellitus. Chemotherapy : drugs against the infecting organism e.g , antimalarial drugs against malarial parasites, or antibiotics against the infecting bacteria or drugs against cancer cells.

6. Mechanism of action Non – receptor mediated Receptor mediated. Non- receptor mediated: by physical action osmosis : some drugs exert effect by osmosis like mannitol . adsorption : some drugs exert effect by adsorption like charcoal adsorbs toxins. demulcent : cough syrup induce soothing effect demulcent coating the inflamed mucosa. radioactivity :radioactive isotopes destroy emit rays and destroy the tissues .

7. By chemical action Antacids are weak bases and neutralize the acids. Metals like iron, copper are eliminated by the chelating agents. These agents trap the metals in their ring structure and make water soluble complexes. through enzymes some drugs act by inhibiting or activating the enzymes drugs acting by antibody production Vaccines act by the production of antibody.

8. placebo effect These are dummy drugs . They are used to relief anxiety. They are also used in clinical trails.

9. Receptor mediated mechanisms Receptors are macromolecular structures present on the cell surface , cytoplasm and nucleus. Drugs bind to the receptors and produce cellular changes. Drug +receptor-----drug –receptor complex------response Affinity : ability of drug to bind to a receptor. Intrinsic activity : ability of a drug to bind to a receptor and produce pharmacological activity called the intrinsic activity of a receptor. Agonist : a drug capable of producing intrinsic activity after binding to the receptor is called the agonist.

10. Antagonist : a drug after binding to the receptor cannot produce the intrinsic activity is called an antagonist. Partial agonist: a drug after binding to the receptor cannot produce full or complete pharmacological activity is called the partial agonist . Inverse agonist : drug has full affinity for the receptor and can produce full pharmacological action but the action is completely opposite to that produced by the agonist.

11. Drug potency The quantity of a drug required to produce desired effect is defined as the potency of drug, The lesser the dose required to produce desired effect the greater will be the potency.

12. Drug efficacy It is the maximum effect of the drug

13. Combined effects of drugs Combination of two or more drugs can increase or decrease the response produced Increased responses Additive effect : the combined effect of two or more drugs is equal to the sum of their individual effects e.g., A+B = Effect of A + effect of B E.g., ibubrufen + paracetamol = effect of both.

14. Potentiation : The enhancement of action of one drug by another drug which is inactive is potentiation . Levodopa + carbidopa Acetylcholine + physostigmine . Carbidopa & Physotigmine inhibit the break down of Levodopa and acetylcholine respectively, thus enhancing their effects.

15. Synergism: When two or more drugs are administered simultaneously their combined effect is greater than that elicited by either drug alone. e.g., Sulphamethoxazole + Trimethoprin , Flucytocine + Amphoteracin B .

16. antagonism There are different types of antagonism. Receptor block (pharmacological antagonism) Competitive antagonism Non-competitive antagonism Chemical antagonism Physical antagonism Physiological antagonism Pharmacokinetic antagonism

17. Drug factors Route of administration: Qunantitative variation: different routs have different variations e.g., morphine when taken orally is needed in a dose of 30—50mgs but given parentrally then the dose required is 5—10mgs. Qualitative variation: magnesium sulphate when given orally acts as a purgative,