Principles of Drugs

Testing of the new drugs before use Not teratogenic ( causes birth defect) Carcinogenic ( causes cancer) Toxicity studies not harmful to body system. It should specific in action and its mechanism of action understood as complitly as possible. Optimal route of administration.

Phases of new drug developments (FDA) Animal Trials Phase 1: the drug is tested on healthy volunteers. Phase 2: involves trials with human subjects who have the disease. Phase 3: large number of patients receive drug to provide information about adverse effect. Phase 4: post market surveillance.

Resources for Drug Information Pharmacopedia Official resource US Pharmacopedia, British Pharmacopedia Compendia Non Official American Formulary, Facts & Comparisons, USP Dispensing Journals Nursing 2005 AJN RN Nursing Reference Books Web sites

Pharmacokinetics Absorption Distribution Metabolism Excretion

Absorption: means the transfer of the drug from the external to the internal environment of the body.

Absorption Oral Preparations Liquids, elixirs, syrups Fastest Suspension solutions ê Powders ê Capsules ê Tablets ê Coated tablets ê Enteric-coated tablets Slowest

Absorption Factors That Affect Absorption Administration route of the drug Food or fluids administered with the drug Dosage formulation Status of the absorptive surface Rate of blood flow to the small intestine Acidity of the stomach Status of GI motility

Distribution The transport of a drug in the body by the bloodstream to its site of action. Protein-binding Water soluble vs. fat soluble Blood-brain barrier Areas of rapid distribution: heart, liver, kidneys, brain Areas of slow distribution: muscle, skin, fat

First-Pass Effect The metabolism of a drug and its passage from the liver into the circulation. A drug given via the oral route may be extensively metabolized by the liver before reaching the systemic circulation (high first-pass effect). The same drug—given IV—bypasses the liver, preventing the first-pass effect from taking place, and more drug reaches the circulation.

Metabolism (also known as Biotransformation) The biologic transformation of a drug into an inactive metabolite, a more soluble compound, or a more potent metabolite. Liver (main organ) Kidneys Lungs Plasma Intestinal mucosa

Factors that decrease metabolism: Cardiovascular dysfunction Renal insufficiency Starvation Obstructive jaundice Erythromycin or ketoconazole drug therapy

Factors that increase metabolism: Barbiturates Rifampin therapy Delayed drug metabolism results in: Accumulation of drugs Prolonged action of the effects of the drugs

Excretion The elimination of drugs from the body Kidneys (main organ) Liver Bowel Biliary excretion Enterohepatic circulation

Half-Life The time it takes for one half of the original amount of a drug in the body to be removed. A measure of the rate at which drugs are removed from the body.

Pharmacodynamics Onset The time it takes for the drug to elicit a therapeutic response Peak The time it takes for a drug to reach its maximum therapeutic response Duration The time a drug concentration is sufficient to elicit a therapeutic response

Pharmacodynamics Drug actions: The cellular processes involved in the drug and cell interaction Drug effect: The physiologic reaction of the body to the drug

The receptor: are protein that may occur on the surface of the cell. They have two important functions: To bind the body own chemical messenger such as hormones and neurotransmitters. To convert into signals that the cell can recognize and respond to. Two important properties: Specificity Affinity

Agonists: the ability of drug to bind receptor (drug that produce response). Antagonist: drug that blocks the action of antagonist. ( Naloxone). Partial agonist: is a drug that is able to both stimulate and block at receptor

Principles of Drug and Dosage Administration Drugs may have more than one indication, i.e. each may have more than one action depending upon dosage Aspirin given in low doses to relieve pain & high doses to suppress inflammation (arthritis) Drugs can be administered by different routes and dosage depends on route given. Oral doses usually larger than injected doses and may be fatal if given by incorrect route Certain IV drugs can cause local injury if intravenous line becomes extravasated.

Guidelines to help ensure correct administration Read medication order carefully Verify identity of patient with drug order. Read medication label & verify Drug itself Amount of drug Verify suitability for administration by intended route Verify dosage calculations Use special handling if drug requires DO NOT ADMINISTER ANY DRUG IF YOU DO NOT UNDERSTAND THE REASON FOR ITS USE

Therapeutic Objective - To provide maximum benefit with minimum harm Therapeutic Objective - To provide maximum benefit with minimum harm. **Must also be ready to respond to interaction between drug and patient (i.e., must be aware of drug REACTIONS and SIDE EFFECTS)**

Evaluating and Promoting Therapeutic Effects Is the drug doing the right thing? Must know rationale for treatment and the nature and time course of desired response If do not have this then cannot make judgment of progress If desired response do not occur then must act quickly. Give alternative therapy Even if patient gains beneficial responses, must be aware of what drug is supposed to do, because it still might end up badly Nifedipine: given for hypertension & angina pectoris: when given to treat hypertension should monitor for reduction in blood pressure; if used for treatment of angina, need to monitor for reduction in chest pain.

Minimize Adverse Effects Know patient history Understand disease and treatment and what drug is supposed to do (again, do not give drug blindly!!!) Identify high risk patient Educate patient Know adverse effects of drug and educate patient. Know drug interactions with other medications This is important part of patient history

Promote Compliance Drugs must be taken correctly Wrong dose Wrong route Wrong time Educate patients to how to self medicate with specific instructions If elderly must also give instructions to another responsible party. Implement Non-drug measures to enhance drug effects Breathing exercises, biofeedback, emotional support, exercise, physical therapy, rest, weight reduction, stop smoking, and sodium restriction (must evaluate individual patient for specific needs)

Patient Education Drug name and therapeutic category (penicillin & antibiotic)- give generic name and trade name Dosage size Dosing schedule (PRN not fixed)-what to do if missed? Route and technique of administration. Expected therapeutic response and when it should develop Non drug measures to enhance therapeutic responses Duration of treatment Method of drug storage

Pharmacology and the Nursing Process Nursing Process 1) assessment 2) nursing diagnosis 3) planning- individual for each patient 4) implementation- some collaborative with physician and others are independent 5) evaluation- degree to which drug therapy is successful

Pre-administration Assessment Establishes the baseline data needed to tailor drug therapy to the individual patient: maximizes benefits and minimizes harmful effects Collection of baseline data needed to evaluate therapeutic responses- beneficial: know the symptoms so you know what baseline data to collect blood chemistry profiles Blood pressure Organ enzyme levels (heart, liver, kidney,…)

Collection of baseline data needed to evaluate adverse effects: Even without baseline data, adverse affects may be obvious (hair loss, pain, vomiting, insomnia) Less obvious are organ functions (liver, kidney,) Identification of high risk patients: Depends on symptoms and drug chosen (if patient has kidney dysfunction and drug is eliminated primarily through kidney, then drug will accumulate and may be toxic) Impaired kidney & liver

Assessment of patient’s capacity for self-care- Must be willing and able to administer drugs in correct dosage and at correct time Evaluate patient intelligence Patient physical capacity to self administer Mental illness (will they take drug?) Financial ability to pay for and get drug Religious beliefs concerning drugs and medications Understanding of patient that drug is needed in prescribed amount (even when they feel better) Assess and discuss with physician

Nursing Diagnoses and Analysis of Drug: Judge appropriateness of prescribed regime Identify potential health problems that drug might cause Determine patient’s capacity for self care Nurse can question appropriateness of drug! must know action of drug contraindications of drug Potential benefits vs adverse reactions to drug Patient history Potential interactions of drug with other medications

Planning Define goals: goal of drug therapy is to provide maximum benefit with minimal harm. Establish Priorities: requires knowledge of drug put together with patient’s unique history. 1st priority is life threatening conditions and reactions that cause acute discomfort that ends in long-term harm Identifying interventions: Drug administration To enhance drug effectiveness To minimize adverse effects and interactions Patient education Establish criteria for evaluation: is drug working?

Implementation of care plan Drug administration Patient education Interventions to promote therapeutic effects Interventions to minimize adverse effects Evaluation Therapeutic responses Adverse drug reactions and interactions Compliance to regimen Satisfactions with treatment How frequent do you evaluate?? Depends on ….. ??? Evaluation by lab tests- baseline data vs current data