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SHM 122 > How drugs work > Flashcards

How drugs work Flashcards

1
Q

Definition of pharmacology

A

Pharmacology is the science of interactions between living systems and chemicals introduced from outside the system

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2
Q

Definition of a drug

A

A drug is a natural/synthetic substance that alters the physiological state of an organism by functioning at a molecular level

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3
Q

Why do drugs not work 100% effectively in reality

A

Only 1-5% of people comply exactly when taking drugs, non compliance is more likely when:

  • More than two administrations a day
  • Dehydration
  • More than three drugs
  • Living alone
  • Greater than 85
  • Busy lifestyle
  • Tiredness
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4
Q

What is the formation of drugs

A

Drugs contain active ingredients and packing chemicals to stabilise/ slow down/ modify release.

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5
Q

What does accumulation of drugs lead to

A

Accumulation of drugs can lead to toxicity

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6
Q

What is the therapeutic range

A

The therapeutic range is the desired range for concentration in the plasma. There may be toxic effects if it goes above or it may not work if it goes below. The size of the therapeutic range varies between drugs.

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7
Q

What does GSL mean

A

GSL means general sales list, drugs that are widely available

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8
Q

What does P mean

A

P means pharmacy only, over the counter

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9
Q

What does POM mean

A

POM means prescription only medication

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10
Q

What is midwives exemption

A

Midwives exemption is a list of medications in section 17 which allows them to supply certain drugs without a prescription

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11
Q

What does PO mean

A

PO means put orally such as a tablet, granule, powder, spray, gel or elixir. This can be swallowing, buccal (inside of cheek), sublingual (under tongue) or lozenges (sucked). It is convenient, cheap and non invasive. However patient may be nil by mouth, vomiting or find it difficult to swallow. Is slow to absorb into the GI tract.

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12
Q

What is inhalation

A

Inhalation is drugs that are inhaled such an entonox or oxygen.

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13
Q

What does PV mean

A

PV means per vaginam such as a propress or prostin. It has a large surface area and a good blood supply for slow, local absorption. However it can be embarrassing and unpredictable or irritate the vaginal wall.

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14
Q

What does PR mean

A

PR means per rectum eg laxatives or analgesics. It is very effective absorption for short term use. However it can be embarrassing and faeces can change absorption rate.

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15
Q

What does topical mean

A

Topical means applied where needed

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16
Q

What does intranasal mean

A

Intranasal means up the nose

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17
Q

What does IM, SC and IV mean

A

IM- intramuscular
SC- Subcutaneous
IV- intravenous

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18
Q

What are the five rights of drug administration

A 
1 Right person 
2 Right time 
3 Right drug 
4 Right dose 
5 Right route
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19
Q 
What do the following abbreviations mean ?
OD 
BD
TDS
QDS
PRN
A 
OD- once daily 
BD- twice daily 
TDS- three times daily 
QDS- four times daily 
PRN- as required, when necessary
20
Q

What are the six factors that affect drug distribution

A

Plasma protein binding, lipid solubility, binding properties, blood flow to organs, stage of life cycle, disease state

21
Q

How does plasma protein binding effect drug distribution

A

Some drugs bind to plasma proteins. The amount that is bound and unbound is in equilibrium. Only the unbound drug is biologically active. The bound drug is stored to be released later.

22
Q

What are the problems with protein binding drugs

A

Plasma proteins can be reduced in pregnancy, malnutrition or in people with excessive burns.

Using two protein binding drugs at the same time effects the equilibrium as they compete for space

Highly protein bound drugs are unlikely to cross the placenta

23
Q

How does lipid solubility effect drug distribution

A

To what extent the drug dissolves in the bodies fatty tissues depends on how much fatty tissue there is and the lipid solubility of the drug.

24
Q

What are the problems with lipid soluble drugs

A

Lipid soluble drugs will cross the placenta. People with a raised BMI will need a larger dose but it will also take longer to clear.

25
Q

How does binding characteristics effect drug distribution

A

Some drugs have unusual binding characteristics which need to be taken into account before administration

26
Q

How does blood flow to tissues effect drug distribution

A

Local and general circulation state determines drug distribution. Some tissues receive a better blood supply than others, meaning they will receive a higher concentration.

27
Q

How does stage of life cycle effect drug distribution

A

Age and pregnancy alter drug distribution

28
Q

How does disease state effect drug distribution

A

Renal/hepatic failure impairs the bodies ability to eliminate most drugs.

Dehydration allows drugs to accumulate

29
Q

What is hypersensitivity

A

The drug acts as an antigen triggering the release of antibodies causing an unpredictable response to the medication

30
Q

Where does metabolism of drugs take place

A

metabolism of drugs takes place in the liver

31
Q

What is anabolism

A

Anabolism is the buildup of substances

32
Q

What is catabolism

A

Catabolism is the breakdown of substances

33
Q

How does the liver metabolise drugs

A

Drugs PO are absorbed through the GI tract and pass through the portal vein to the liver then to the general circulation. Drugs given by other routes reach the liver after the general circulation. There are then metabolised by liver enzymes.

34
Q

What problems can occur in the liver during drug metabolisation

A

Liver enzymes are effected by malnutrition, alcoholism, age and liver disease. They can also become accustomed to the environment and adapt. Many drugs such as alcohol and caffeine induce (speed up) liver enzymes, and high doses can inhibit them.

35
Q

How does the kidneys metabolise drugs

A

Kidneys metabolise drugs through glomerular filtration then tubular secretion and reabsorption.

36
Q

What is a GFR

A

A GFR is a glomerular filtration rate. It is a blood test to check how well the kidneys are working. The creatinine levels are tested and combined with other factors.

37
Q

What factors cause a low GFR

A

Dehydration, age, ACE inhibitors, NSAIDs, heart failure, shock and renal disorder

38
Q

What is a half life

A

A half life is the time taken for the concentration of a drug in the plasma to fall to half of its maximum volume.

39
Q

What is a steady state

A

the steady state is the rate of drug elimination which is equal to the rate of administration.

40
Q

What is a loading dose

A

A dose of drug given in emergencies so as to not wait 3-5 half lives for the therapeutic range.

41
Q

How do drugs work on cell receptors

A

Drugs with the same or similar structure to natural ligands can bind to receptors and either active the cells usual actions or block them.

42
Q

What us down regulation

A

Down regulation is a reduced number and action of cell receptors due to continued presence of a drug

43
Q

How do drugs work on ion channels

A

Ion channels facilitate the diffusion of ions across membranes. Some drugs bind to ion channels and modulate/block them.

44
Q

How do drugs work on enzymes

A

Some drugs bind to enzymes and catalyse/ inhibit thier action.

45
Q

What are non specific drugs

A

Some drugs work due to their physiochemical properties rather than the shape of their molecules to produce non-specific actions.

46
Q

What are some of the possible effects of drugs

A

1) the main action (can be an extreme of the desired effect)
2) the subsidary action (act on another cell)
3) cell damage
4) hypersensitivity

SHM 122 (14 decks)

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