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YEAR 1 Pharmacolgy > How Does The Body Handle Drugs? > Flashcards

How Does The Body Handle Drugs? Flashcards

0
Q

Why use oral administration?

A
  1. convenient for patient.

2. Large surface area for absorption in the small intestine.

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1
Q

What is the sequence of drug disposition?

A

Intake–> absorption–> distribution–> drug/cell interaction–> metabolism–> excretion.

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2
Q

Absorption of a drug can depend on…

5 answers…

A
  1. How lipid soluble the drug is
  2. The stomach contents, eg, does the stomach contain milk or tetracycline.
  3. The rate of gastric emptying.
  4. Degradation in the stomach.
  5. First pass metabolism.
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3
Q

During degradation in the stomach…

A

Parietal cells secrete HCl,
Chief cells secrete digestive enzymes.

This leads to low bioavailability of the drug.

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4
Q

What is bioavailability?

A

The amount of dose which reaches the blood circulation as intact drug.

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5
Q

The first pass metabolism of a drug is…

A

The hectic first-pass effect.

This leads to low bioavailability.

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6
Q

Why use topical administration?

A
  1. Convenient for patient - can take drug at home.

2. The drug is poorly absorbed so risk of overdose is reduced.

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7
Q

Disadvantages of topical administration?

A

Negative effect on skin.

An example of this is that hydrocortisone causes thinning of the skin.

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8
Q

Why use transdermal administration?

A
  1. Long acting.
  2. Useful when you want low blood levels over a long period of time.
  3. Can be used in a wide range of patient groups.
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9
Q

Disadvantages of using transdermal administration?

A
  1. Can cause skin irritation.
  2. Variable absorption.
  3. Drug must be very lipid soluble.
  4. Drug must be very potent.
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10
Q

Why use rectal administration?

A
  1. Local or systemic effect.

2. Useful in patients who are vomiting or unable to swallow.

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11
Q

Disadvantage of using rectally administered drugs?

A

The person administering the drug must be specially trained to do so.

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12
Q

Examples of drugs administered rectally…

A
  1. Some analgesics.
  2. Diazepam.
  3. Prednisone.
  4. Anti-fungals.
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13
Q

Why use inhalation to administer a drug?

A

Can cause rapid changes in the plasma concentration of a drug due to huge surface area in lungs with good blood supply.

Also causes a local or systemic effect.

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14
Q

Disadvantages of using inhalation?

A

Difficult to ensure that the drug reaches the site of action.

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15
Q

Examples of drugs that can be inhaled…

A
  1. Halothane.
  2. Nitrous oxide.
  3. GTN
  4. Salbutamol.
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16
Q

What are the parenteral routes of administration?

6 routes…

A
  1. Intravenous. Eg heparin.
  2. Intramuscular. Eg pre-meds.
  3. Intradermal. Eg local anaesthetic and allergy screening.
  4. Subcutaneous. Eg insulin.
  5. Intrathecal (into subarachnoid space) eg chemotherapy drugs.
  6. Epidural. Eg nerve blockers during labour.
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17
Q

Advantages of using parenteral routes of administration?

A
  1. Rapid action.
  2. Bypasses stomach and liver.
  3. Lower dose can be used.
  4. Patient controlled analgesia - syringe drivers.
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18
Q

Disadvantages of using parenteral routes?

A
  1. Trained person is required to administer the drug.2. Extreme care in required.
  2. Accidental overdoses may become more likely.
  3. Can be painful, especially intramuscular injections.
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19
Q

What are the formulations of a drug?

A

Tablets, capsules, granules, powders, gels, emulsions, suspensions, syrups, solutions, creams, pastes, ointments, lotions, implants, transdermal patches, aerosols, sprays, inhalations and gases.

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20
Q

Definition of a medicine?

A

An active drug plus added excipients.

Excipients= inactive ingredients that act as a vehicle for the active drug.

21
Q

The formulation of a drug can impact upon…

A

The bioavailability of the drug and the length of the therapeutic effect.

22
Q

Sequence of drug absorption when taken orally…

A

Tablets—> granules—> fine particles—> solution—> ABSORPTION!

23
Q

Sites of absorption in oral administration?

A
  1. Stomach

2. Small intestine.

24
Q

Ways a drug can move across a membrane…

A
  1. Passage through water channels.
  2. Endocytosis.
  3. Passive diffusion.
  4. Facilitated diffusion.
  5. Active transport.
25
Q

How does facilitated diffusion work?

A
  1. Drug moves down concentration gradient.
  2. Proteins form channels for drug to move through.
  3. No energy is needed.
  4. It is a selective process.
26
Q

How does active transport work?

A
  1. Drug moves against the concentration gradient.
  2. Energy is needed.
  3. Selective process.
27
Q

What happens during distribution?

A

The drug is transferred in and out of various tissues from the bloodstream.

28
Q

What effects the extent of distribution?

A
  1. Lipid solubility of drug
  2. Blood flow to tissue/organ
  3. Binding of drug to proteins.
29
Q

Which organ receives the most blood flow?

A

The kidneys.

30
Q

What is the protein called that free drugs can bind to in the plasma?

A

Albumin

31
Q

Which type of drug can diffuse across the membrane and have an effect?

A

Free or unbound drugs.

32
Q

Why do drugs bound to the protein not have an affect?

A

It is now too big to bind to the target site.

33
Q

What is the aim of metabolism?

A

To turn lipid soluble drug into a water soluble drug using an enzyme.

34
Q

What are the stages of drug removal?

A

Metabolism and excretion.

35
Q

Most drugs are…

A

Lipophilic, this means they will recirculate in the bloodstream.

36
Q

Stages of metabolism…

A

Lipid-soluble drug—> Water-soluble drug (easy to loose in urine)—> Water-soluble drug is excreted.

37
Q

Where does metabolism take place?

A

Mainly in liver in the smooth endoplasmic reticulum. However it also takes place in the kidneys, lungs, GI tract, brain and Plasma.

38
Q

Phases of metabolism?

A

Phase 1 and phase 2. Phase 2 can sometimes go before phase 1.

39
Q

What happens during phase 1?

A
  1. The chemical structure of the drug is altered.
  2. The drug becomes slightly more water soluble.
  3. The products can be more chemically reactive than parent drug.
  4. This is know as ‘pharmacological activation’.
40
Q

What happens during phase 2?

A
  1. The drug is stuck to other large molecules such as amino acids.
  2. The greater molecular weight means that the drug is now less lipid soluble and more easy to excrete now that it is water soluble.
  3. Drug becomes inactive, ‘pharmacological inactivation’.
41
Q

Drug metabolising enzymes can be induced by…

A

Alcohol and carbamazepine, which induce liver enzymes.

This reduces the duration of drug action.

42
Q

Drug metabolising enzymes can be inhibited by…

A

Fluoxetine and grapefruit juice.

This increases the duration of drug action which may not be ideal.

43
Q

What is excretion?

A

The removal of a drug from the body.

44
Q

How is a drug excreted?

A

Through urine, bile, faeces, lungs and skin.

45
Q

To increase drug excretion there must be…

A

Increased blood flow to kidneys and decreased protein binding.

46
Q

The therapeutic response of most drugs is related to…

A

The level of drug in the plasma.

47
Q

What is half life?

A

The time it takes for the amount of drug in the body to decrease to one-half of the peak level.

48
Q

Half life is the rate at which drugs are…

A

Eliminated from the body.

49
Q

Most of a drug is eliminated in…

A

5 half lives.

50
Q

Why is half life important?

A

Helps to avoid drug interactions.

YEAR 1 Pharmacolgy (5 decks)

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