Pharm 1000065 Lecture Notes (Lec 2) PDF

Pharm 1000065 ( Lec 2 ) 😀 Concentration of drug in body that produces the desired effect with minimal or no signs of toxicity or lack of effect Importance of the “Rights” in Drug Administration Right patient Verify patient identity Right time Important to maintain de...

Pharm 1000065 ( Lec 2 ) 😀 Concentration of drug in body that produces the desired effect with minimal or no signs of toxicity or lack of effect Importance of the “Rights” in Drug Administration Right patient Verify patient identity Right time Important to maintain desired therapeutic effect and avoid toxicity Right drug 4 times to check: Removal from storage, Dispensing, When returning to pharmacy, Before giving to patient Right strength Right documentation Legal & safety obligation; owner must consent to treatment Right route & technique Right patient weight Right dosage Right dose How to get within the Therapeutic Range Afftected by drug & Animal health / physiology Administering drug correctly & At ideal of time ensures efficacy of drug Drug Dosage Mass of drug required per unit of body weight (e.g., 2 mg/kg) Drug Dose Calculated mass of drug administered at one time (e.g., dose = drug dosage x body weight) Dose Interval The frequency at which a dose is administered (e.g., every 24 hours) Dose Forms Physical form of drug administered Loading Dose Increased initial dose to quickly reach therapeutic range Maintenance Dose Dose that keeps drug in therapeutic range Total Daily Dose  Mass of drug given over 24 hours Therapeutic Index TI = LD50/ED50 Drug A with higher TI is safer than Drug B Drug A TI = LD50/ED50= 100mg/kg / 2mg/kg= 50 ( safer ) Drug B TI = LD50/ED50= 10mg/kg / 2mg/kg= 5 Safety Doses If lethal dose is much larger than effective dose Drug has a ______High____ margin of safety = high therapeutic index If effective dose is close to lethal dose: Drug has a _____Low_____margin of safety = low therapeutic index Routes of Administration Parenteral Routes Excludes small intestine (enteral routes) IV Injection Fastest way to achieve drug effects; immediate response; 100% bioavailability Immediate response Know concentration of drug in blood  2 Techniques Bolus ( Concentration amount ) Drug --> diluted in small amount of fluid immediate high concentration of drug Infusion ( Delivered over long period of time --) s , min , hrs Famotidine electrolyte & nutrition CRI ---> Analgesics , anesthetics IM Injection Absorbed rapidly, can be a depot preparation / resository Many sting SQ Injection Into connective tissue, faster than oral, can give large volumes Faster Than PO , Slower Than IM Local Routes of Administration Inhalant Rapid absorption due large surface area Volatized --> drug turn into Gas Nebulized --> drug turn into fine spray / mist Lung ---> alveoli ---> blood capillaries Topical  Skin, eyes, ears Dissolve, then penetrate skin ---> diffusion (lower concentration) Localized Tx affected by fur, feathers, & organic debris Systemic absorption slowest benefit from a high concentration drug compared to the rest of body Oral Administration Slower onset compared to parenteral routes do not need " sterile " product 3 event ---> before reach systemic circulatiom dissolve dose form to ---> release drug ( liberation ) pass from Gi Tract ---> vascular system pass though the liver ( ' first pass effect ) Pharmacokinetics (PK) effect body on drug Absorption Movement from administration site into the systemic circulation ( In vascular system ) Distribution Physiological movement to tissues Around Metabolism Chemical alteration, primarily in the liver Changed Excretion Elimination from body Out Pharmacodynamics (PD) Effect of drug on the body including depression, stimulation, destruction, irritation, and replacement Mechanisms for Drug Movement Passive Diffusion Movement from high concentration to low, no energy required Facilitated Diffusion Assisted by carrier proteins, no energy required Active Transport Energy required, moves against concentration gradient Pinocytosis & Phagocytosis Pinocytosis ---> cell drinking ( ex: insulin , b12 absorb from GI tract ) Phagocytosis ---> cell eating ( ex : anti absorb from colostrum ) Energy required Step 1 : Absorbtion Movement of drug from site of administration into systemic circulation Effect by many factor Patient Dose Form Body construction & Functioning Surface area / Blood supply / GI Tract Route ( IM / SQ - ECF vs PO - PPB ) Route ( solubility , ionization , molecule size , pKa pH of environment drug is in PO Drugs Fast absorption : molecules in lipophilic form for fatty membrane Must be dissolved in GI Fluid before absorption Water typically ↑ Parenteral drugs fast absorption : molecules in Hydrophilic form for ECF Tissue blood flow to site Temperature of patient Step 2 : Distribution Factors effect by ---> Membrane permeability, protein binding, tissue perfusion, and blood flow rates Step 3 : Metabolism Factors Primary site : liver Secondary site : Kidneys , small itntestine , brain , nervous tissue , lung , skin 4 Main : oxidation , Reduction , Hydrolysis , Conjugation Step 4 : Excretion Routes Primarily through urine or bile; consideration for milk in lactating animals  Through : Kidney , Liver , Intestine , lungs , milk saliva , sweat Effects on the Body Affinity Strength of binding between drug and receptor Drug Interactions Drug-Food Interactions Can alter drug absorption/effectiveness Drug-Drug Interactions Can lead to antagonistic, additive, or synergistic effects Side Effects Commonly gastrointestinal, neurological, or dermatological; should be reported for patient safety