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nb401 > Pharmacology > Flashcards

Pharmacology Flashcards

1
Q

The 3 Types of Pharmacology

A
  1. Pharmaco-kinetics

what the body does to the drug eg breakdown of paracetamol

  1. Pharmaco-dynamics

what the drug does to the body eg paracetamols actions

  1. Pharmaco-therapeutics

the use of drugs to treat diseases eg paracetamol’s effect on pain & body temperature

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2
Q

What is Pharmaco-kinetics?

A
  • Movement of drugs through the body
  • Body processes affecting the drug
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3
Q

Prescence of the drug in the body is influenced by what?

A

-absorption (GI tract/parenterally)
-distribution (circulatory system)
-metabolism/elimination (Liver/other enzyme)
-excretion (urine via kidney typically)

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4
Q

What are the Parental Routes of Administration?

A
  • Sub-cutanous
  • Intra-muscular
  • Intra-venous
  • Intra-osceous
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5
Q

What are the Non-Parental Routes of Administration?

A
  • Transdermal (absorption patch)
  • Rectal
  • Oral
  • Sublingual/Buccal
  • Inhaled
  • Nebulised
  • ETT (endotracheal tube)
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6
Q

What Happens During Oral Administration?

A
  • Subjected to same digestive processes, pH changes and enzymes as food
  • Will then be absorbed from stomach/intestines
  • Making a drug alkaline will mean its favoured to be absorbed in small intestine which is alkaline
  • Must then pass-through liver via hepatic portal system before entering the general circulation (first pass effect
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7
Q

Advantage/Disadvantage of Sublingual/Buccal Administration

A
  • Avoids GI tract/liver
  • Provides rapid administration as drug is absorbed into the bloodstream
  • Bad taste and poor application area
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8
Q

Advantages of Rectal Administration

A
  • Avoids inactivation of stomach acid and digestive enzymes
  • About 50% of drug passes through the liver, entering circulatory system
  • Advantageous if patient is unconscious, vomiting or fitting
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9
Q

Inhalation Administration

A
  • Lungs have very large SA and good blood supply, suitable for absorption
  • Small particles favour systemic absorption over larger particles
  • nebulised form = liquid inhaled as fine spray or gas
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10
Q

Injection Administration

A
  • Drugs injected by SC/IM routes have to diffuse between lose connective tissue/muscle fibres
  • Good blood supply increase absorption rate as will heat/massage area
  • ‘Depot’ injections give slow, sustained drug release
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11
Q

What are the Topical Administration Methods?

A
  • Most drugs easily absorbed through skin but may be formylated into dermal patches for slow systemic absorption eh contraceptive patches, GTN
  • Eye drops to conjunctiva, ear drops and application to skin to treat local infection
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12
Q

What is the IST Pass Effect?

A
  • Many drugs metabolised by liver (95% of paracetamol) - may inactivate the drug. So, in liver failure won’t break down and be very potent (Iv route will avoid this)
  • Example: Glyceryl trinitrate (GTN) has a very large first pass effect and cannot be taken orally
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13
Q

What is Bioavailability?

A
  • The proportion of administered drug actually reaching the systemic circulation after going through the stomach, intestine and liver.
  • Meaning only a proportion of the administered dose will actually reach the target cells
  • When a drug is injected intravenously the total dose is immediately available to exert a therapeutic effect – it is said to have 100% bioavailability
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14
Q

Protein Binding

A
  • When absorbed, drug can bind to plasma proteins
  • This is reversible. Drug can be specific to a protein
  • Only unbound drugs have physiological effects
  • In bound form, they form ‘reservoirs’ of inactive drug as in low conc, drug elimination by metabolism/excretion may be delayed. This effect is responsible for prolonging the effect of drug
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15
Q

Absorbtion Properties of Drugs

A
  • Drugs can be destroyed by stomach acid eg benzyl penicillin or digestive enzymes
  • Strongly hydrophobic drugs are poorly absorbent as insoluble in aq body fluids
  • Many drugs require protein carrier
  • Strongly hydrophilic drugs are unable to cross lipid rich cell membranes
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16
Q

Physiological Factors that Reduce Absorption

A
  • Rapid intestinal tract time
  • Reduced circulation to organ (shock)
  • Prescence of food decreases absorption
  • Stress slows down inactivity of the |GI tract/delays gastric emptying
  • 1st pass effect
17
Q

Absorbtion: Transport Across Membranes

A

Drugs are mainly absorbed by ‘passive’ or ‘active’ transport

Passive transport - Drug moves down a ‘concentration gradient’ by diffusion

Active transport - requires cellular energy to move against concentration gradients e.g across the blood brain barrier

18
Q

Ways of Increasing Distribution

A
  • Blood Flow - drugs distribute faster with high blood flow organs
  • Solubility - If its water or lipid soluble
  • Size of patient - the large the body the decrease the concentration of dose per unit
19
Q

What is Metabolism?

A

Refers to the body’s ability to change a drug from its dosage form to a more water-soluble state for excretion. Usually done by enzymes

20
Q

What are Substances Metabolised into?

A

Either inactive metabolites or inti metabolites that themselves metabolise

21
Q

Where are the Majority of drugs metabolised?

A

The liver including 2nd metabolic process to aid excretion (conjugation)

22
Q

Where does else does metabolism take place?

A

Plasma, kidneys and intestines

23
Q

Factors Affecting Metabolism

A

extremes of age, genetic differences, nutritional factors, stress & lifestyle/environmental factors – all can reduce availability of enzymes

24
Q

Metabolism

A
  • Some drugs inhibit or compete for enzyme metabolism causing accumulation of drugs when given together (paracetamol & caffeine, paracetamol & alcohol)
  • Certain diseases can reduce metabolism like cirrhosis of liver & heart failure due to failure of enzyme production & reduced blood flow
25
Q

Plasma Half Life (T 1/2)

A
  • The time it takes for the concs of drugs to half in plasma. Is linked to speed of elimination/duration of action
  • Determines frq of administration
  • A drug administered at regular intervals reaches a steady concentration (‘steady state’) when the rate of administration = threat of elimination - approximately 5x the half life
26
Q

Excretion of Drugs

A
  • Most excreted by the kidneys, leave body via urine
  • Renal immaturity/dysfunction therefore delays excretion/accumulation may occur
27
Q

What is Pharmaco-dynamics?

A

Drugg affects depends on what target cell is capable off accomplishing

A drug can modify target cells function by:

  • inhibiting enzymes that normally have an effect on the cell
  • acting directly on cell membranes, blocking channels
  • Interacting w/ a receptor to stimulate or block it
28
Q

Receptor Theory

A
  • Why one drug can be targeted at 1 specific biochemical function
  • The 3D shape means its structure is complementary
  • They fit together, drugs can be highly specific
29
Q

Selectivity

A
  • Ranges based on shape/structure
  • Drugs can be specific to a certain receptor = selective
  • If a drug works on a variety of receptors it’s called non-selective and can cause widespread, unwanted side effects
  • The better the fit the better the response. Complete attachment is called agonists
  • Drugs that attach but give no response = antagonist
  • Drugs that attach and elicit a small response but also block other responses are called partial agonists
30
Q

Agonists and Antagonists

A

Agonists eg opiates
- Work by stimulating or blocking receptors
- Have an ‘affinity’ for the receptors they stimulate

Antagonists
- Have an affinity for a receptor but do not stimulate it – they ‘jam the lock’
- Therefore, preventing a response from occurring – may be used as ‘antidotes’ in the event of over dosage with an agonist

31
Q

Therapeutic Index

A

The dose that will give 50% of patients determined effect

32
Q

Therapeutic Window

A

Puts time against a drug working too much producing side effects or working then not working due to too much time passing and concentration of drug decreasing.

33
Q

What is the difference between Tolerance and Dependence?

A

Tolerance
- Occurs when a patient has a decreased response to a drug over time due to the body becoming more effective at eliminating it
- Patient requires larger doses to produce the same response

Dependence:
- Patient displays a physical or psychological ‘need’ for the drug

34
Q

The Three Types of Drug Interactions

A
  • Additive - 2 similar drugs taken at the same time w/ decreased dosages to not push into side effect profile but give the same overall effect
  • Potentiation - add drug to increase effectiveness of another drug eg caffeine
  • Negatory
35
Q

Adverse Drug Reactions

A
  • An undesirable and sometimes unpredictable response to a drug
  • Range from mild & transient, to potentially life-threatening
  • Most are predictable and dose-related, eg. known side-effects/unwanted effects (‘secondary effects’)
36
Q

Tyes of Adverse Reactions

A
  • Type A (Dose Related)
  • Type B (Non-Dose Related)
37
Q

Type A (Dose Related)

A
  • Predictable & caused by excess of drug’s wanted pharmacological effect
  • Sometimes a drug’s parallel unwanted action
  • Usually caused by incorrect dosage (too high) especially common in elderly
38
Q

Type B (Non-Dose Related)

A

Hyper-susceptibility (specific to an individual patient):
- Patients can experience an XS therapeutic response or secondary effects
- May be due to altered pharmacokinetics, leading to higher-than-expected blood concentrations, or increased receptor sensitivity

Iatrogenic (resulting from treatment):
- Mimic pathological disorders eg ulceration/ irritation of the GI tract by aspirin

Patient sensitivity and allergy:
- Less common as drug-related reaction - patients’ unexpected and extreme sensitivity to a drug
- Previous exposure to a drug which sensitizes the immune system - subsequent exposure produces hypersensitive reaction
- Range from very mild to full-blown anaphylaxis response

nb401 (14 decks)

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