Pharmacology: Lecture Slides

Pharmacology Weeks 1 & 2 Relevance to PT +How drugs impact exercise +How exercise impacts the drug +How drugs impact healing +PT educate patients on drugs & look for adverse drug reactions +Great resource for looking up drug info: drugs.com Be alert +Prescribing errors are common +Many people ta...

Pharmacology Weeks 1 & 2 Relevance to PT +How drugs impact exercise +How exercise impacts the drug +How drugs impact healing +PT educate patients on drugs & look for adverse drug reactions +Great resource for looking up drug info: drugs.com Be alert +Prescribing errors are common +Many people take multiple drugs +Sticking to the regimen is difficult +Drugs have more than one name +Chemical, generic, trade +Drugs on market during Phase 4 Risk of abuse +Schedules 1-5* +I Highest abuse risk (e.g. LSD, marijuana, etc) +V Lowest abuse risk (e.g. cough medicines) Drug therapy- +Administration (oral, IV, injection, etc) +We will discuss the following in the upcoming slides- +Absorption +Systemic circulation +Distribution +Target tissues +Metabolism (liver/kidney) Dose response curve +Provides info on dosage range when drug is effective +Peak response time + Time for drug to have max benefit +Ceiling effect/maximal effect- + Level at which there is no longer a response no matter how much more drug you give +Potency- absolute amount of drug required for desired effect + The more potent, the less drug needed  Drug safety +Quantal dose +Dose response based on % of people responding to drug +Median effective dose- Dose when 50% of folks have the response +Median toxic dose- Dose when 50% of folks have adverse effects +Medial lethal dose- Dose that caused 50% death in animal studies +Therapeutic index (toxicity/effectiveness) +Drug’s safety margin- the greater this value, the safer it is +Must be > 1 (or effective dose would equal toxic dose) +Example: Digitalis TI = 2 (requires close monitoring). Small dose can be toxic +Penicillin has TI > 100. Very safe. Large dose needed for toxicity  Pharm Principles +Pharmacokinetics*- what the body does w/ the drug +After administration (oral, rectal, vascular, etc)- 1. Absorption- movement of drug across membranes 2. Distribution- movement of drug in body 3. Metabolism- process of making drugs more or less active 4. Excretion- removal of drug from body The first-pass effect is a pharmacological phenomenon in which a medication undergoes metabolism at a specific location in the body. The first-pass effect decreases the active drug's concentration upon reaching systemic circulation or its site of action Pharm Principles The first-pass effect: when medication undergoes metabolism at a specific location in the body (most often the liver). The first-pass effect decreases the active drug's concentration upon reaching systemic circulation or its site of action. If first pass-effect is a major concern, methods of drug administration may need to be altered.  Bioavailability* Is how much of the drug reaches systemic circulation +Depends on administration and absorption +Ex: if 100mg of a drug was orally given and 50mg reaches systemic circulation, the drug is 50% bioavailable. +This same drug could be 100% bioavailable if injected perhaps Distribution- impacted by 1. Tissue permeability +Can the drug pass through cell membranes 2. Blood flow +Exercising will influence, areas w/ greater blood flow will get more drug 3. Binding to plasma proteins +Drug bound to plasma proteins are not available for target tissues 4. Binding to subcellular components +Drugs can be bound in specific cells and not widely available Storage +Storage Drugs can be temporarily stored in other areas away from target tissue +Can have adverse consequences if a substance builds up (e.g. lead poisoning- stored in organs and bones/teeth) + Adipose- consider BMI of your patient (*a primary storage site) + Bone- more toxic drugs + Muscle- can be long term storage + Organs- e.g. liver, kidney New methods of delivery +Newer Delivery Methods +Controlled-release: a preparation that allows the drug to move through body more slowly to enhance absorption +Implanted drug delivery w/ electronic control +Targeted delivery- monoclonal antibodies that get attached to drugs (e.g. cytotoxic drugs for cancer tx) are attracted to specific antigens, for instance on tumor cells  More pharmacokinetics 1. *Biotransformation- drug metabolism/breaking it down +Oxidation- O2 added or H removed +Reduction- opp of oxidation +Hydrolysis- break into separate parts +Conjugation- coupling +Biotransformation occurs in +Liver (*most common site), lungs, kidney, GI system, integumentary system Pharmacokinetics 1. Enzyme induction +Prolonged use of some drugs induces the body to enzymatically destroy the drug more rapidly (e.g. tolerance)- Drug holiday needed 2. Biological half life +Time needed for drug to decrease in plasma concentration by ½ +This means the shorter the half life, the more frequent the doses needed  Methods of drug excretion +Urination- kidneys +Exhalation- lungs +Defecation- colon +Sweating- skin Question +If a drug has a half life of 60 seconds, how much drug remains of 12mg dose after 2 minutes? Factors to consider- all impact how drugs work +Meals/drinks +Activity +Time of day +Body mass +Type of diet (pH) +Hydration status +Age +Disease state