HLTAP501A – Analyse health information

1. HLTAP501A – Analyse health information TOPIC 8: Pharmacological processes and drug actions LRP p65 Unit Assessment: Category D exam x2

2. Definition: • Pharmacology is the study of all drugs, legal and illegal including their actions, effects and how they affect living systems (Bryant et al, 2003).

3. Define terms relating to pharmacology: • pharmaceutics • pharmacokinetics • pharmacodynamics • pharmacy • medicine/medication.

4. ACTIVITY 1 . • Pharmaceutics: the science of preparation and dispensing of drugs. • Pharmacokinetics: the way a drug is altered as it travels through the body by absorption, distribution, metabolism and excretion or how the body affects a drug after administration.

5. Activity 1 cont: • Pharmacodynamics: what drugs do to the body and how they do it, the interaction of drug molecules with their target receptors or cells and their biochemical, physiological and therapeutic or adverse effects.

6. Definitions cont: • Pharmacy: the branch of science dealing with preparing and dispensing drugs, the place wherethis function is carried out. • medicine / medication: drugs given for therapeutic purposes, may be a mixture of substances.

7. Drug characteristics: To differentiate between the broad definitions of the word drug, which could mean any substance that is ingested (as all ingested substances affect the body), useful medications are defined by the following characteristics: • potency • selectivity • specificity

8. ACTIVITY 2 • potency: the term potency refers to the amount of a chemical required to produce an effect. The more potent a drug, the lower the dose needed to produce an effect. • Selectivity: the narrowness of a drug’s range of actions on particular receptors, cellular processes or tissues

9. Activity 2 cont • Specificity: the narrowness of the range of actions of a drug eg cardiospecific ß-blockers are less likely to cause asthma as they are specific for ß1 receptors, which are found mainly in cardiac tissue. It may also refer to the relation between the chemical structure of a drug and its pharmacological actions.

10. Revise types of drug actions / reactions: • therapeutic effects • side effects • adverse effects • idiosyncratic reactions • toxic reactions • allergic reactions.

11. ACTIVITY 3 (p94 med admin) • therapeutic effects: desired response • side effects: known or expected reaction • adverse effects: any drug effect other than the one intended • idiosyncratic reactions: unpredictable, individual and unusual

12. Activity 3 cont • toxic reactions: result from cumulative effect and resulting build up of a drug • allergic reactions: sensitised to drug, causing reactions such as skin rashes fever etc. eg aspirin  asthma attack, penicillin anaphylactic shock.

13. * • everything that is ingested has the potential to affect the body; therefore there is a duty of care surrounding medication administration that is implicit.

14. Basic information that a health professional should be aware of before dispensing medication: • approved generic name • drug group or category • pharmacodynamic effects • mechanisms of action

15. Basic information that a health professional should be aware of before dispensing medication cont: • particular pharmacokinetic parameters • indications for clinical use • common adverse effects • contraindications and precautions • significant drug interactions • monitoring techniques.

16. Legal and ethical foundations for pharmacotherapy • Drugs are controlled at many levels’ international, national and state. Laws apply to the classification and control of chemicals, poisons drugs and other therapeutic goods. • Some chemicals are prescribed for therapeutic use under various legal Acts. Criminal law relates to offences under these Acts.

17. Drug regulation: • The Australian Therapeutic Goods Administration, a section of the commonwealth Department of Health, provides a framework for the regulation of therapeutic goods to ensure their safety, efficacy, quality and timely availability. The National Poisons Scheduling Committee imposes controls on drugs by setting the Standards for the Uniform Scheduling of Drugs and Poisons and deciding into which schedule a drug, poison or other chemical should be placed. The schedules relating to drugs are numbered 2,3,4 and 8

18. Molecular aspects of drug action: • Drugs modify existing physiological, biochemical and biophysical functions. Drugs act by binding proteins which are the molecular target or site of action. Ideally drugs should interact with only one target at one site and have only one effect. Unfortunately no drugs do this, although drugs do show selectivity namely a preference for a molecular target. Selectivity depends on the chemical structure of the drug, its molecular size and electrical charge. Changes in these parameters can alter the therapeutic effect or cause toxicity (Bryant el at, 2003).

19. Pharmacodynamics: molecular aspects of drug action: • agonists • antagonists • drug absorption, distribution, metabolism and excretion p91 • pharmacokinetics and dosing

20. Drugs which bind can be: (i) agonists - drugs that bind to a receptor of a cell - an agonist binds to and activates the receptor & produces a response by the cell agonist produces an action - an agonist often mimics the actions of a naturally occurring substance - when a drug is administered, the response usually increases in proportion to the dose until the receptors are saturated - until it produces the therapeutic effect

21. Drugs which bind can be (cont): (ii) antagonists - an antagonist binds to a receptor and blocks access, thus diminishing the normal response - drugs may act as competitive ` antagonists (reversible) or irreversible antagonists - they are often known as “blockers” – blocks an action.

22. Pharmacodynamics: molecular aspects of drug action cont: • Absorption, distribution, metabolism and excretion - for a drug to produce an effect it must reach its molecular target. - the concentration that a drug attains at its site of action is influenced by the rate and extent to which a drug is: --absorbed into body fluids --distributed to the sites of action --metabolised into active or inactive metabolites --excreted from the body by various routes e.g. kidneys, liver, sweat.

23. ACTIVITY 5 • Give six (6) examples of drugs which are agonists e.g. dopamine agonists • Give six (6) examples of drugs which are antagonists e.g. insulin and glucagon

24. . Pharmacokinetics and dosing Rational use of drugs is based on the assumption that a particular concentration of a drug will have the desired therapeutic affect and that adverse effects will be negligible. (i) therapeutic range: is generally considered to reflect the range of drug concentrations having a high probability of producing the desired therapeutic effect and a low probability of producing adverse effects. Pharmacokinetics plays a large role in establishing initial dosages and adjustment of regimes as well as dealing with lack of response or to reducing symptoms of toxicity.

25. Pharmacokinetics and dosing cont (ii) clearance: this is the ability of an organ or the body to eliminate a drug. Clearance determines the maintenance dose rate required to achieve the plasma concentration at a steady rate

26. Pharmacokinetics and dosing cont (iii) loading dose: is the initial amount of drug required to fill the volume of distribution.

27. Pharmacokinetics and dosing cont (iv) half-life: is the time taken for the blood or plasma concentration to fall by one half (50%) Half-life is the major determinant of the duration of action of a drug after a single dose, the time taken to reach steady state (when the rate of drug administration equals the rate of drug administration) with chronic dosing and the dosing frequency required to avoid massive fluctuations in plasma drug concentration during the dosing interval. The factors influencing half-life include volume of distribution and clearance

28. Pharmacokinetics and dosing cont (v) volume of distribution: the volume in which the amount of drug in the body would need to be uniformly distributed to produce the observed (measured) concentration in the blood.

29. New drug development • When a company initiates development of a new drug, they have to conform to stringent processes before the drug can be utilised for human consumption. Legal requirements remove unsafe or ineffective drugs from reaching the marketplace.

30. stages of new drug development: • new idea • pharmacology • toxicology studies • pharmaceutical formulation • application to drug-regulating authorities for testing on humans • clinical trial if drug appears worthwhile • application for drug registration • on-going post market studies

31. ACTIVITY 6: Look up a common medication used in each body system and research under the following headings: • approved generic name • drug group or category • pharmacodynamic effects • mechanisms of action • indications for clinical use • common adverse effects • contraindications and precautions • significant drug interactions • any special monitoring eg regular blood tests.