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HH2 > Introduction to Pharmacology > Flashcards

Introduction to Pharmacology Flashcards

1
Q

WHAT IS PHARMACOLOGY

A
  • The study of effects of drugs on the function of living systems
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2
Q

PHARMACODYNAMICS

A
  • Where a drug acts in the body (site of action)

- Biochemical, physiological and behavioral effects of drug (mode of action)

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3
Q

PHARMACOKINETICS

A
  • 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
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4
Q

ORAL ROUTE OF ADMINISTRATION

A
  • 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
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5
Q

DIFFICULTIES WITH ORAL ROUTE

A
  • 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
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6
Q

SUMMARY OF ROUTES OF ADMINISTRATION AND DRUG DISTRIBUTION IN THE BLOOD

A
  • 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
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7
Q

Oral bioavailability

A

The fraction of orally administered drug that reaches the systemic circulation

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8
Q

Bioequivalence

A

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

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9
Q

Intravenous: Absorption pattern

A
  • Precise, accurate and potentially immediate effects (absorption phase is bypassed)
  • Suitable for large volumes and mixtures
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10
Q

Intravenous: Special Unity

A
  • Valuable for emergency use, permits titration of dose

- Usually required for high molecular weight protein and peptide drug

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11
Q

Intravenous: Limitations and precautions

A
  • 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
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12
Q

THERAPEUTICS

A

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

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13
Q

CHEMOTHERAPY

A

Use of drugs to kill or weaken invading cells or organisms

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14
Q

TOXICOLOGY

A

Study of poisons and the treatment of poisoning

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15
Q

HOW DRUGS WORK

A
  • 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
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16
Q

ORIGINS OF DRUGS

A
  • 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)
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17
Q

PHYSICAL NATURE OF DRUGS

A
  • 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
Q

DRUG NOMENCLATURE 1

A
  • 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
Q

DRUG NOMENCLATURE 2

A
  • 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
Q

THE THERAPEUTIC DRUG MARKET 1

A
  • 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
Q

THE THERAPEUTIC DRUG MARKET 2

A
  • 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
Q

S8- Controlled drug

A
  • Available only on separate prescription form; prior authority of Department of Health required. E.g. Morphine, amphetamine/methylphenidate
23
Q

S7- Dangerous Poisons

A

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

24
Q

S6- Industrial and Ag. poisons

A

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

25
Q

S5- Domestic type poisons

A

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

26
Q

S4- Prescription Only

A

Drugs available only from pharmacists on prescription

27
Q

S3- Pharmacist Only Medicine

A

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

28
Q

S2- Pharmacy Medicine

A

Drugs available without prescription from pharmacists or poisons licence holders only

29
Q

WHAT IS AN AGONIST?

A
  • 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
Q

WHAT IS AN ANTAGONIST?

A
  • 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
31
Q

What is affinity

A

Relative tendency of a drug to combine with its receptors

The response of the cell is a product of affinity and intrinsic activity

32
Q

What is intrinsic activity of efficacy

A
  • Capacity of a drug to produce a pharmacological effect after binding to its receptor (ie.e the maximal possible effect that can be produced by the drug) (E-max)
  • The response of the cell is due to affinity and intrinsic activity
33
Q

Agonists possess?

A

Affinity and intrinsic activity

34
Q

Antagonists possess

A

Affinity but lack intrinsic activity

35
Q

Partial agonist

A

Compound which interacts with a receptor but produces less than the maximum effect- less intrinsic activity or efficacy

36
Q

Potency

A
  • Inherent ability of a drug to combine with receptors
  • Depends on drug affinity
  • Important for dosage but unimportant characteristic of a drug for clinical purposes as long as it can be administered conveniently
  • No justification that the more potent of 2 drugs is clinically superior (toxicity is also important)
  • Usually stated in absolute terms (e,g 10mg/kg)
37
Q

Maximal effect (Emax)

A
  • Maximal efficacy- plateau in the dose response (DR) - curve
  • Dependent on intrinsic activity of the drug
  • Potency vs efficacy- whereas potency refers to the concentration of drug required to produce a particular effect, efficacy refers to the maximal possible effect that can be produced by the drug
38
Q

DRUG TOXICITY

A
  • Potency provides little info about the dose of a drug at which toxic effects manifest themselves
  • Determined from the LD50 (median lethal dose) (dose of drug that is lethal to 50% of subjects)
  • Thus therapeutic index (LD50/ED50) gives an idea of the relative margin of safety of a drug
  • Greater this ratio, the safer the drug
  • Must be greater than 1.0 to be therapeutic agent, less than 2.0 typically see toxicity at therapeutic dose
39
Q

DESENSITISATION AND TACHYPHYLAXIS 1

A
  • Synonymous terms- a drug effect which gradually diminishes over a few seconds to minutes

Causes:

  • Change in receptors→ receptor resulting in tight binding of agonist without opening of ion channel
  • Loss of receptors- Endocytosis during prolonged exposure
  • Exhaustion of mediators- Depletion of neurotransmitters or second messengers
40
Q

TOLERANCE

A
  • Takes days or weeks to develop
  • Need to increase dosage in order to achieve same therapeutic response (e.g. morphine)

Causes:

  • Increased metabolic degradation→ induction of metabolic enzymes
  • Physiological adaptation → e.g. side effects, (nausea, sleepiness) sometimes tend to subside

HH2 (17 decks)

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