General Pharmacology Lecture Notes PDF

# General Pharmacology By Dr/ Ola Salem ## Pharmacokinetics - Actions of body on drugs (ADME) Pharmacokinetics: The principles of ADME - Absorption: How will it get in? - Metabolism: How is it broken down? - Distribution: Where will it go? - Excretion: How does it leave? ## Pharmacodynamics...

# General Pharmacology By Dr/ Ola Salem ## Pharmacokinetics - Actions of body on drugs (ADME) Pharmacokinetics: The principles of ADME - Absorption: How will it get in? - Metabolism: How is it broken down? - Distribution: Where will it go? - Excretion: How does it leave? ## Pharmacodynamics - Actions of a drug on the body ## Passage of Drugs Across Cell Membrane - **Passive Transport** - Simple Diffusion - Filtration - **Special Transfer** ## Simple Diffusion - Simple Diffusion through water pores. - Simple Diffusion through lipid membrane. ## Factors Affecting Simple Diffusion - Concentration - Molecular weight - Soluble in water - Lipid soluble (high oil/water partition coefficient) - Ionization ## Ionization - Low ionization = high lipid solubility and better passage. - It depends on pH and pKa. - pKa = pH at which 50% of drug is ionized. - Degree of ionization is determined by Henderson Hasselbalch equation. For weak ACID: $pKa = pH + log \frac{Unionized}{Ionized form}$ For weak BASE: $pKa = pH + log \frac{Ionized}{Unionized form}$ ## Rules - Acidic drug become more NON ionized in acidic PH. - Aspirin: Stomach - Alkaline urine - Basic drugs become more NON ionized in basic pH. - Amphetamine: Intestine - acidic medium ## Filtration - Passage of drugs through capillary endothelium and glomeruli. - **Criteria:** - Not bound to plasma proteins - MW < 500 - High osmotic and hydrostatic gradient ## Special Transfer - ***Pinocytosis*** - Extracellular fluid - Substances - Plasma membrane - Cytoplasm - Vesicle - ***Active Transport*** - Diffusion - Facilitated Diffusion - Active Transport - Passive Transport ## Absorption - Parenteral: IV, IM, SC - Sublingual - Inhalation - Oral - Transdermal patch - Rectal - Topical ## Factors Affecting Absorption ### A- Factors Related to the Drug - Water and lipid solubility - Degree of ionization - Valency - Nature - Preparation and dosage form ### B- Factors Related to the Patient - Routes of drug administration - Systemic circulation - Absorbing surface - Specific factors - Other drugs ### C- Specific Factors for Oral Absorption - Gastric emptying - Gut motility - pH - Food and other drugs (food-irritant drugs-milk-tea-cholystyramine) ## Bioavailability (f) - The fraction of administered drug that reaches the systemic circulation in an unchanged form. - Intravascular doses have 100% bioavailability, f = 1. - Bioavailability = $\frac{area under curve (AUC) of the route}{area under curve (AUC) of IV route} * 100$ ## First Pass Effect - Drug metabolism before it reaches systemic circulation so the concentration will reduce. - ***Gut First Pass*** (acidity: penicillin, digestive enz: hormones and proteins, gut wall: l-dopa). - ***Hepatic First Pass*** (nitroglycerin, lidocaine). - How to overcome? ## Thank you