Principles of Drugs

1. Principles of Drugs

2. 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.

3. 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.

4. 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

7. Pharmacokinetics • Absorption • Distribution • Metabolism • Excretion

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

10. Absorption • Oral Preparations Liquids, elixirs, syrups FastestSuspension solutions êPowders êCapsules êTablets êCoated tablets êEnteric-coated tablets Slowest

11. 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

12. 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

13. 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.

14. 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

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

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

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

18. 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.

19. 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

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

21. 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

22. 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

23. 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.

24. 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

25. 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)**

26. 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.

27. 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

28. 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)

29. 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

30. 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

31. 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,…)

32. 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

33. 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

34. 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

35. 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?

36. 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