Pharmacology

Ideal Drug  Effectiveness  Safety  Selectivity  Reversible  Predictability  Ease of administration  Freedom from drug interactions  Low cost  Chemical Stability  Possession of a simple

Ideal Drug  generic name

Therapeutic Objective  Maximum benefit with minimum harm  The intensity of the response to a drug is directly related to the concentration of the drug at its site of action

Intensity of Drug responses  Administration – dosage and route  Pharmacokinetics  Pharmacodynamics  Individual variation

Nursing Responsibilities  Last line of defense against errors!!!!!!!!!  Patient education  Utilize the nursing process

Drug Legislation  1906 – drugs should be free of adulterants  1938 – testing for toxicity  1962 – proof of effectiveness  1970 – Controlled Substance Act – Scheduled drugs  1997 – Food and Drug Administration Modernization Act

Drug Names  Chemical  Generic Name  Trade Name  OTC drugs

Pharmacokinetics  Drug movement throughout the body  Absorption – movement of drug from its site of administration into blood  Dissolve – must dissolve before being absorbed  Surface area – the larger the faster  Blood flow – most rapid where blood flow is high  Lipid solubility - the higher the faster  pH partitioning

Routes of Drug Administration Routes of Drug Administration

Drug Absorption  Absorption is the process by which a drug enters the bloodstream without being chemically altered or  The movement of a drug from its site of application into the blood or lymphatic system

Drug Absorption  The rate at which a drug reaches it site of action depends on: –Absorption - involves the passage of the drug from its site of administration into the blood –Distribution - involves the delivery of the drug to the tissues

Routes of Drug Administration The route of administration (ROA) that is chosen may have a profound effect upon the speed and efficiency with which the drug acts  The possible routes of drug entry into the body may be divided into two classes: –Enteral –Parenteral ImportantInfo

Enteral Routes  Enteral - drug placed directly in the GI tract: –sublingual - placed under the tongue –oral - swallowing (p.o., per os) –rectum - Absorption through the rectum

Sublingual/Buccal Some drugs are taken as smaller tablets which are held in the mouth or under the tongue.  Advantages –rapid absorption –drug stability –avoid first-pass effect  Disadvantages –inconvenient –small doses –unpleasant taste of some drugs

Oral  Advantages –Convenient - can be self- administered, pain free, easy to take –Absorption - takes place along the whole length of the GI tract –Cheap - compared to most other parenteral routes

Oral

 Disadvantages –Sometimes inefficient - only part of the drug may be absorbed –First-pass effect - drugs absorbed orally are initially transported to the liver via the portal vein –irritation to gastric mucosa - nausea and vomiting

Oral  Disadvantages cont. –destruction of drugs by gastric acid and digestive juices –effect too slow for emergencies –unpleasant taste of some drugs –unable to use in unconscious patient

First-pass Effect

1. unconscious patients and children 2. if patient is nauseous or vomiting 3. easy to terminate exposure 4. absorption may be variable 5. good for drugs affecting the bowel such as laxatives 6. irritating drugs contraindicated Rectal

Parenteral Routes –Intravascular (IV, IA)- placing a drug directly into the blood stream –Intramuscular (IM) - drug injected into skeletal muscle –Subcutaneous - Absorption of drugs from the subcutaneous tissues –Inhalation - Absorption through the lungs

Intravascular Absorption phase is bypassed (100% bioavailability) 1.precise, accurate and almost immediate onset of action, 2. large quantities can be given, fairly pain free 3. greater risk of adverse effects a. high concentration attained rapidly b. risk of embolism c. OOPS factor or

Intramuscular 1. very rapid absorption of drugs in aqueous solution 2.repository and slow release preparations 3.pain at injection sites for certain drugs

Subcutaneous 1. slow and constant absorption 2. absorption is limited by blood flow, affected if circulatory problems exist 3. concurrent administration of vasoconstrictor will slow absorption

1.gaseous and volatile agents and aerosols 2.rapid onset of action due to rapid access to circulation a.large surface area b.thin membranes separates alveoli from circulation c.high blood flow Particles larger than 20 micron and the particles impact in the mouth and throat. Smaller than 0.5 micron and they aren't retained. Inhalation

Topical Mucosal membranes ( eye drops, antiseptic, sunscreen, callous removal, nasal, etc.) Skin a. Dermal - rubbing in of oil or ointment (local action) b. Transdermal - absorption of drug through skin (systemic action) i. stable blood levels ii. no first pass metabolism iii. drug must be potent or patch becomes to large

 intravenous seconds  intraosseous seconds  endotracheal 2-3 minutes  inhalation 2-3 minutes  sublingual 3-5 minutes  intramuscular minutes  subcutaneous minutes  rectal 5-30 minutes  ingestion minutes  transdermal (topical) variable (minutes to hours) Route for administration -Time until effect-

Metabolism  LIVER  Enzymatic alteration of drug structure

Considerations in Metabolism  Age  Induction of drug metabolizing enzymes  First-pass effect – Nitroglycerin  Nutritional status  Competition between drugs

Excretion  KIDNEY  Glomerular filtration – blood to tubular urine  Tubular reabsorption  Active tubular secretion – pumps for organic acids and organic bases – to urine

Monitoring drug levels  Plasma drug levels Therapeutic range

Drug Half-life  Time requires for the amount of drug in the body to decrease by 50%  Will determine dosing requirements  Goal - plateau

Receptors  Drugs bind to receptors to produce effects  Reversible

Drug – Food Interactions

 Frequently decreased rate of absorption  Grapefruit juice can inhibit metabolism  “with food” – with or shortly after meal  “empty stomach” – one hour prior to meal or two hours after

Adverse drug reactions  Side effect  Toxicity  Allergic reaction  Idiosyncratic effect  Iatrogenic disease  Physical dependence  Carcinogenic effect

 Teratogenic effect – induce birth defect  Ways to minimize