Pharmacology Flashcards
1
Q
The 3 Types of Pharmacology
A
- Pharmaco-kinetics
what the body does to the drug eg breakdown of paracetamol
- Pharmaco-dynamics
what the drug does to the body eg paracetamols actions
- Pharmaco-therapeutics
the use of drugs to treat diseases eg paracetamol’s effect on pain & body temperature
2
Q
What is Pharmaco-kinetics?
A
- Movement of drugs through the body
- Body processes affecting the drug
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)
4
Q
What are the Parental Routes of Administration?
A
- Sub-cutanous
- Intra-muscular
- Intra-venous
- Intra-osceous
5
Q
What are the Non-Parental Routes of Administration?
A
- Transdermal (absorption patch)
- Rectal
- Oral
- Sublingual/Buccal
- Inhaled
- Nebulised
- ETT (endotracheal tube)
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
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
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
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
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
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
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
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
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
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
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
Plasma Half Life (T 1/2)
- 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
Excretion of Drugs
- Most excreted by the kidneys, leave body via urine
- Renal immaturity/dysfunction therefore delays excretion/accumulation may occur
27
What is Pharmaco-dynamics?
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
Receptor Theory
- 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
Selectivity
- 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
Agonists and Antagonists
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
Therapeutic Index
The dose that will give 50% of patients determined effect
32
Therapeutic Window
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
What is the difference between Tolerance and Dependence?
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
The Three Types of Drug Interactions
- **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
Adverse Drug Reactions
- 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
Tyes of Adverse Reactions
- Type A (Dose Related)
- Type B (Non-Dose Related)
37
Type A (Dose Related)
- 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
Type B (Non-Dose Related)
**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
