Introduction to Pharmacodynamics for beginners

Introduction to pharmacodynamics

1. Pharmacodynamics Lectured by Dr. Subed Chandra Dev Sharma Professor Dept. of Biochemistry and Molecular Biology, RU

2. Pharmacodynamics Study of the action of drug and the biochemical and physiological effects produced by the drug action. “What the drug does to the body” or “ the effects of a drug on the body ”

3. Antacids Ach on Nicotinic receptors Folic acid synthesis inhibitors Catecholamines -------> ↑ Heart rate Anesthetics-------- > ↓ depress the CNS Atropine----- > x Ach action Insulin ----- > Diabetes Anticancer drugs/ Antibiotics-------- > ◌ infecting organism/cancer cells Eucalyptus oil ---- > treating cough and muscle pain, insect repellent

4. Extra cellular site of action 1.Antacids neutralizing gastric acidity. 2.Chelating agents forming complexes with heavy metals. 3.MgSO4 acting as purgative by retaining the fluid inside the lumen of intestine. Cellular Site of Action 1.Ach on Nicotinic receptors of motor end plate, leading to contraction of skeletal muscle. 2.Effect of sympathomimetics on heart muscle and blood vessels. Intracellular site of action -Folic acid synthesis inhibitors. Folic acid which is intracellular component essential for synthesis of proteins and DNA and RNA. Trimethoprim and sulfa drug interfere with synthesis.

5. Stimulation • Some of drugs act by increasing the activity of specialized cells. Ex: Catecholamines stimulate the heart and Heart rate, Force of contraction Inhibition • Some drugs act by decreasing the activity of specialized cells. Ex: Barbiturates, General anesthetic, these drug depress the CNS system. Atropine inhibits Ach action. Replacement • When there is a deficiency of endogenous substances, they can replaced by drugs. Ex: Insulin in Diabetes mellitus, Throxine in cretinism and myxedema Irritation • Certain drugs on topical application cause irritation of the skin and adjacent tissues. These drugs are using for counter irritant. Ex: Eucalyptus oil, methyl salicylates (Used in sprains, joint pain, myalgia. Cytotoxic • Treatment of infectious disease/cancer with drugs that are selectively toxic for infecting organism/cancer cells Ex: Anticancer drugs, All Antibiotics

6. or

7. Agonist Antagonist Partial agonist I nverse agonist  

8. Epinephrine → β adrenoreceptors → increased heart rate , myocardial contractility Isoproterenol → β adrenoreceptors → increased heart rate → used in bradycardia Agonist

9. Buprenorphine → μ- opioid receptor → weak morphine-like activity  → in pain management Endorphins → μ- opioid receptor → perception of pain ↓ /ꭓ, increase feelings of wellbeing ↑ Epinephrine → β adrenoreceptors → increased heart rate , myocardial contractility, contraction of vascular smooth muscle Propranolol → β adrenoreceptors → No activity → used in high blood pressure Antagonist Partial agonist

10. In  pharmacology , an  inverse agonist  is a  drug  that binds to the same  receptor  as an  agonist  but induces a pharmacological response opposite to that of the agonist. Gamma-aminobutyric acid (GABA) is an amino acid that functions as the primary inhibitory neurotransmitter for the central nervous system (CNS). It functions to reduce neuronal excitability by inhibiting nerve transmission. I nverse agonist   Benzodiazepines → GABA receptor → slow down CNS activity → used in anti-anxiety, muscle relaxant properties Β -Carboline → GABA receptor → neuronal excitability ↑ → used in anti-depressant