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Flashcards in Introduction to Pharmacology Deck (40)
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1

WHAT IS PHARMACOLOGY

- The study of effects of drugs on the function of living systems

2

PHARMACODYNAMICS

- Where a drug acts in the body (site of action)
- Biochemical, physiological and behavioral effects of drug (mode of action)

3

PHARMACOKINETICS

- The way in which the drug concentration changes over time
- How drugs get into the body, move around the body and leave the body, or, (Absorption, Distribution, Metabolism, Excretion)
- Quantitative pharmacokinetics (measure concentration of drug at various times)
- Allows one to make intelligent decisions regarding dose and frequency of drug administration

4

ORAL ROUTE OF ADMINISTRATION

- Enteral , p.o (per os)
- Most common route
- Usually safet
- Most convenient
- Most economical
- Because of its natural physiology and function, the intestine is the major site of drug absorption following oral administration

5

DIFFICULTIES WITH ORAL ROUTE

- First pass metabolism
- Before entering the systemic circulation, blood leaving the GI tract passes through the liver→ drugs that are highly metabolised by liver may attain very low circulating levels relative to those obtained after parenteral administration

6

SUMMARY OF ROUTES OF ADMINISTRATION AND DRUG DISTRIBUTION IN THE BLOOD

- With most routes of administration the drug will enter the bloodstream and be taken round the body BEFORE passing through the liver
- For example if a drug is given by intramuscular injection it gets absorbed through small blood vessels in the muscle and gets taken directly to the heart and pumped around the body
- First pass metabolism
- Drugs taken orally are absorbed in the stomach and small intestine
- Blood vessels take the drug directly to the liver
- Drug passes through liver before being distributed round the body

7

Oral bioavailability

The fraction of orally administered drug that reaches the systemic circulation

8

Bioequivalence

2 drugs with identical chemical composition that yield different blood concentration and different effectiveness, differ in bioavailability (and are not bioequivalent)

9

Intravenous: Absorption pattern

- Precise, accurate and potentially immediate effects (absorption phase is bypassed)
- Suitable for large volumes and mixtures

10

Intravenous: Special Unity

- Valuable for emergency use, permits titration of dose
- Usually required for high molecular weight protein and peptide drug

11

Intravenous: Limitations and precautions

- Greater risk of adverse effects (high concentration attained rapidly, risk of embolism)
- Must inject solutions slowly as a rule
- Not suitable for oil solutions or poorly soluble drugs

12

THERAPEUTICS

Use of drugs used to cure, treat or prevent disease and in the alleviation of pain and suffering

13

CHEMOTHERAPY

Use of drugs to kill or weaken invading cells or organisms

14

TOXICOLOGY

Study of poisons and the treatment of poisoning

15

HOW DRUGS WORK

- The majority of drugs interact with specific molecule s involved in regulatory functions (e.g. a receptor or drug receptors active site on an enzyme (drug target ))
- A small number of drugs interact with chemicals in the body but are not bound to a tissue component
- Osmotic diuretics (mannitol) or osmotic laxatives (sorbitol) will bind to water in the kidney
- Antacids will bind to acid in the stomach

16

ORIGINS OF DRUGS

- Some drugs are synthesised within the body (e.g. hormones, autacoids, neurotransmitters) this includes insulin, oestradiol, adrenaline and testosterone
- Most drugs are not synthesized within the body
- Xenobiotics (e.g. synthetic or semisynthetic drugs)
- Posions
- Toxins (poisons of biologic origin)

17

PHYSICAL NATURE OF DRUGS

- Solid (aspirin, paracetamol)
- Liquid (ethanol)
- Gaseous (Nitrous Oxide)
- These factors often determine route of administration
- Some liquid drugs are easily vapourised and can be inhaled

18

DRUG NOMENCLATURE 1

- Chemical name- N-acetyl-p- aminophenol (identifies chemical structure)
- Generic name- official name (lower case) (e.g. paracetamol)
- Trade name- Proprietary/brand name (first letter capitalised) (E.g. Panadol)

19

DRUG NOMENCLATURE 2

- Generic drugs belonging to the same drug group (often) have the same suffix
- Most antianxiety drugs (benzodiazepines) ‘-azepam’ e.g. diazepam,
- Local anaesthetics ‘-caine’ (e.g. lignocaine, cocaine)
- Mot beta-receptor antagonists ‘-olol’ (e.g. propranolol, metoprolol)

20

THE THERAPEUTIC DRUG MARKET 1

- 700 active ingredients

Multiple combinations (e.g.)
- Panadeine= codeine + paracetamol
- Tylenol Sinus= Paracetamol + pseudoephedrine

Delivery forms (e.g.)
- Adalat Oros= Slow release nifedipine tablets (once daily)
- Adalat= nifedipine tablets (twice daily)

Over 30,000 different medicinal drug products on Australian market

21

THE THERAPEUTIC DRUG MARKET 2

- The availability of potentially dangerous drugs and chemicals needs to be restricted to enable their safe and effective use
- Scheduling is the legal process used to achieve this (Therapeutic Goods Act 1989)
- Medicinal drugs (therapeutic goods) includes:
- Prescription and non-prescription products from synthetic and biological sources, herbal products, vitamin and mineral supplements, sunscreens and homeopathic products
- Unscheduled drugs can be sold through other retail outlets such as supermarkets (e.g. paracetamol)

22

S8- Controlled drug

- Available only on separate prescription form; prior authority of Department of Health required. E.g. Morphine, amphetamine/methylphenidate

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S7- Dangerous Poisons

Contains many substances requiring Department of Health authority to obtain, use or supply

24

S6- Industrial and Ag. poisons

No restriction on sale; special packaging and storage requirements with warnings and first aid directions

25

S5- Domestic type poisons

No restriction on sale or storage; special packaging requirements with warnings and first aid directions

26

S4- Prescription Only

Drugs available only from pharmacists on prescription

27

S3- Pharmacist Only Medicine

Drugs available without prescription only from a pharmacist who must hand product to customer

28

S2- Pharmacy Medicine

Drugs available without prescription from pharmacists or poisons licence holders only

29

WHAT IS AN AGONIST?

- Drug, hormone or neurotransmitter that elicits a biological effect when it interacts with receptors- e.g. bethanechol (used for urinary retention) combines with muscarinic receptor
- Bethanechol mimics action of ACh (the neurotransmitter at these receptors)
- Magnitude of signal depends on number of receptors occupied and/or rate of formation of drug-receptor complexes
- An agonist that can bind to a receptor has an AFFINITY for that receptor
- When an agonist binds to a receptor it can produce a pharmacological response. The agonist therefore has INTRINSIC ACTIVITY

30

WHAT IS AN ANTAGONIST?

- A drug which interacts with a receptor, does not elicit a biological effect and blocks or reverses effect of an agonist-
E.g. atropine (muscarinic receptor- antagonist-smooth muscle relaxant)
- An antagonist that can bind to a receptor has an AFFINITY for that receptor
- When an antagonist binds to a receptor it does not produce a pharmacological response, the agonist therefore has NO INTRINSIC ACTIVITY
- An antagonist however, can prevent agonists from binding to the receptor