PHARM CH1 (1) (2).pptx

CHAPTER 1: GENERAL PHARMACOLOGY Introduction  What is a drug?  Any substance used to diagnose, prevent or treat disease  The veterinary technician’s role:  Administration of drugs  Filling patient prescriptions  Client education (indications, contraindications, possible adverse effects) ...

CHAPTER 1: GENERAL PHARMACOLOGY Introduction  What is a drug?  Any substance used to diagnose, prevent or treat disease  The veterinary technician’s role:  Administration of drugs  Filling patient prescriptions  Client education (indications, contraindications, possible adverse effects) Drug Sources  Plants  alkaloids – end in –ine  glycosides – end in –in  gums, resins, oils  Bacteria & Molds  Animals  hormones & anticoagulants  Minerals  electrolytes, iron, selenium  Laboratories Pharmacotherapeutics  Drug selection  Diagnostic: follows assessment of patient & identification of the causative microorganism or altered physiological state  Empirical: uses of practical experience & common sense  Symptomatic: treats symptoms of disease  $$$ Pharmacotherapeutics  Regimen: plan for administering the drug  route of administration  dose  frequency  duration  Prescription drug: drug limited to use under the supervision of a veterinarian because of potential danger, difficulty of administration, or other considerations  “Caution: Federal law restricts this drug to use by or on the order of a licensed veterinarian.” Pharmacotherapeutics  Veterinarian-client-patient relationship: set of circumstances that must exist between veterinarian, client & patient before the dispensing of prescription drugs is appropriate  Conditions required for a valid veterinary-clientpatient relationship:  assumed responsibility  sufficient knowledge  follow-up Pharmacotherapeutics  Responsibilities of the technician  Correct drug  Correct route & time  Observe response of the animal  Question unclear orders  Create & affix labels accurately  Explain administration instructions to clients  Record appropriate information in medical record Pharmacokinetics  What happens to drugs once they enter the body  Absorbed into bloodstream & distributed to various fluids & tissues  Must reach target site & accumulate at required concentration to be effective  Body immediately starts to break down & excrete  Loading dose: initial high dose used to reach appropriate blood level  Steady state: point at which drug accumulation equals drug elimination  Therapeutic drug monitoring: used to measure drug levels in blood, urine, CSF fluid or other appropriate fluid Pharmacokinetics  Factors that influence blood concentration levels & patient response  Rate and amount of drug Absorption  Distribution throughout the body  Metabolism/biotransformation  Rate & route of Excretion  “ADME” Pharmacokinetics  Selection of route of administration  Available form of drug  Physical or chemical properties  Onset of action  Use of restraint or behavioral characteristics  Nature of condition Drug Absorption  Bioavailability: degree to which a drug is absorbed & reaches the general circulation  Factors that affect absorption  Mechanism of absorption  pH & ionization status of drug  Absorptive surface area & blood supply to the area  Solubility of the drug  Dosage form  Status of GI tract  Interaction w/ other medications Drug Absorption  Passive absorption/transport – no energy required  simple diffusion  facilitated diffusion  Pinocytosis – energy required  Active transport – energy required Passive transport Pinocytosis Active transport Drug Distribution  Absorption→plasma→interstitial fluid→cell→receptors  Rate of movement is based on concentration gradient (difference b/w amounts of drug in 2 compartments)  Protein bound drugs are inactive & unavailable; storage sites  Tissues w/ natural barriers – brain, eye, placenta  Disease processes that can interfere w/ – abscesses, heart failure & shock & kidney, renal or liver failure Biotransformation/Metabolism  Body’s ability to change a drug chemically from the form in which it was administered into a form that can be eliminated from the body Biotransformation Biotransformation/Metabolism  Chemical reactions that occur in the liver  Oxidation: loss of electrons  Reduction: gain of electrons  Hydrolysis: splitting of drug molecule w/ addition of water molecule  Conjugation: addition of glucuronic acid resulting in more water soluble molecule Biotransformation/Metabolism  Factors that can alter  Species  Age  Nutritional status  Tissue storage (fat and plasma proteins)  Health status Drug Excretion  Kidneys  glomerular filtration & tubular secretion  urine  Liver  bile → sm. intestine → feces or reabsorbed into blood  Mammary glands, lungs, intestinal tract, sweat glands, salivary glands & skin Drug Excretion  Residues: drug that remains in animal products when they are consumed  Half-life: time required for the amount of drug present in the body to be reduced by half Pharmacodynamics  Study of mechanisms by which drugs produce physiologic changes in the body  Affinity: tendency of a drug to combine w/ a receptor  Efficacy: degree to which a drug produces its desired response  Potency: amount of drug needed to produce a desired effect Drug Pharmacodynamics  Agonist: drug w/ a high level of affinity & efficacy which causes a specific action  Antagonist: drug that blocks another drug from combining w/a receptor * *A partial agonist will have similar action as the agonist + antagonist. Pharmacodynamics  Therapeutic index: relationship b/w a drug’s ability to achieve the desired effect its tendency to produce toxic effects  LD50/ED50  Quantitates drug’s safety margin  Adverse drug reaction: undesirable response to a drug  Allergic, photosensitivity, abortion, L/K damage, infertility, V/D & cancer  Idiosyncratic drug rxn: unusual or unexpected rxn peculiar to an individual Drug Interactions  Altered pharmacologic response to a drug caused by the presence of a 2nd drug  Normal response can be increased or decreased  Beneficial or harmful  Classifications  Pharmacokinetic Plasma or tissue levels of a drug are altered by the presence of another  Pharmacodynamic Action or effect of 1 drug is altered by another  Pharmaceutic Occurs when physical or chemical rxns take place as a result of mixing drugs Drug Names  Chemical – describes the molecular structure of a drug  Code or laboratory – name given to a drug by R&D  Compendial – name listed in the US Pharmacopoeia  Official – usually same as above or generic name  Proprietary or trade – name chosen by the manufacturing company; ®; begins w/ capital letter  Generic – common name chosen by company (patents expired or patent never issued); begins w/ lowercase letter Drug Name Example  Chemical – 6-chloro-α-methyl-9H-carbazole-2-acetic acid  Code or laboratory – ???  Compendial – carprofen  Official – carprofen  Proprietary or trade – Rimadyl, Novox, Norocarp, Vetprofen  Generic – carprofen Drug Labels  Must contain  Drug names (generic & trade)  Concentration & quantity  Name & address of manufacturer  Controlled substance status  Control or lot #  Expiration date  Instructions for use & warnings or possible adverse effects (insert)  Withdrawal time (if applicable) Drug Labels Development & Approval of New Drugs  Regulatory agencies  FDA – development and approval of drugs and feed additives through its Center for Veterinary Medicine  EPA – development and approval of animal topical pesticides  USDA – development and approval of biologics (vaccines, serums, antitoxins)  The Food Animal Residue Avoidance Databank (FARAD) – database of residue avoidance info. (withdrawal/withholding times) and educational materials Development & Approval of New Drugs  Steps in the development of a new drug  Preliminary trials – product tested on bact., yeast or molds, computer models used to simulate animal models  Preclinical (animal safety) trials – lab animals used to determine appropriate doses; few target animals may be used  Clinical trials – product tested on target animal  Submission of a new animal drug application  Final review by the FDA (EPA or USDA)  Product monitoring Federal Law Related to Drug Development & Use  The Animal Medicinal Drug Use Clarification Act (AMDUCA)  Made extralabel use of approved veterinary drugs legal under specific well-defined conditions  FDA may prohibit extralabel use if it finds that such use presents a risk to public health  Some drugs are prohibited for extralabel use in food animals  See handout Compounding of Veterinary Drugs  Conditions approved by FDA  Identification of a legitimate veterinary need  Need for an appropriate regimen for a particular species, size, gender or medical condition  Lack of an approved animal or human drug that when used as labeled will treat the condition  Too long a time interval for securing the drug to treat the condition Federal Law Related to Drug Development & Use  The Veterinary Feed Directive (VFD)  Established a new category of drugs as “an alternative to prescription status” for certain antimicrobial animal feed additives  The Minor Use & Minor Species Animal Health Act (MUMS)  Intended as a mechanism to provide FDA-authorized drugs for less common species & indications Marketing of Drugs  Vet-VIPPS – voluntary certification program created by the National Assoc. of Boards of Pharmacy & advocated by the AVMA to validate the legitimacy of online pharmacies  Ethical products – products for which the manufacturer has voluntarily limited their sale to veterinarians as a marketing decision