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SL12102 - the science of medicines > L2 - what is a medicine? > Flashcards

L2 - what is a medicine? Flashcards

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1
Q

what is drug absorption?

A

the uptake of non-metabolised drug after the release from its formulation, from the site of delivery to the systematic circulation

(drug is getting across a biological membrane with exception of intravenous delivery)

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2
Q

what are the routes of delivery for drugs?

A
  • oral
  • injections
  • implants (long term delivery + subcutaneous)
  • topical (creams and ointments) and transdermal (across skin into systemic circulation)
  • pulmonary (inhalation)
  • nasal
  • buccal (mouth) and sublingual (under the tongue)
  • ocular, otic (ear)
  • rectal, vaginal
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3
Q

types of injections

A

intravenous, intramuscular, subcutaneous (fatty tissue under skin), intradermal (into layers of skin)

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4
Q

what does drug absorption involve?

A

drug crossing a biological barrier(s)

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5
Q

Is there an absorption process in IV administration?

A

no. drug directly into blood

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6
Q

what is biopharmaceutics?

A

aim of medicines design is to get the right drug to the right place at the right dose and at the right rate.

pharmaceutics optimises drug delivery

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7
Q

what is a drug?

A

active pharmaceutical ingredient (API) that is responsible for the medicines therapeutic effect

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8
Q

what is a medicine?

A

drug (API) and everything else (excipients) long list of ingredients.

MASS OF DRUG ON LABEL.

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9
Q

what is the dosage form?

A

the physical form that a medicine is produced and administered, e.g tablets, creams, aerosols

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10
Q

what are tablets?

A

solid forms that are swallowed

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11
Q

what are capsules?

A

containers (gelatin) filled with medicine

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12
Q

what are liquids?

A

solutions, suspensions, emulsions

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13
Q

what are topicals?

A

creams, ointments, gels applied to skin

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14
Q

what are inhalers?

A

devices that deliver medication directly to lungs

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15
Q

considerations in design of dosage form?

A
  1. physiochemical properties of drug (some drugs suitable for certain dosages, but some not)
  2. biopharmaceutical considerations (how the administration route of dosage form affects rate and extent of absorption)
  3. therapeutic considerations (dose you want to deliver and the rate at which you want to deliver it)
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16
Q

time of onset of action of intravenous injections?

A

seconds

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17
Q

time of onset of intramuscular + subcutaneous injections + buccal tablets + aerosols + gases

A

minutes

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18
Q

time of onset of solutions, tablet etc (oral dosage forms)

A

mins to hours

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19
Q

time of onset of enteric coated formulations (protects it from being dissolved in stomach so dissolves in small intestine instead)

A

several hours

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20
Q

time of onset of implants and depot injections

A

days to weeks

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21
Q

time of onset of topical preparations

A

varies

22
Q

what is a drug delivery system (DDS)?

A

process of administering drug to achieve a therapeutic effect. focuses on the technology used to deliver drug to target site.

23
Q

what are controlled release systems?

A

tablets/ capsules designed to release slowly overtime

24
Q

what are transdermal patches?

A

patches applied to skin that releases medicine over long time

25
Q

what are injectable systems?

A

intravenous and intramuscular

26
Q

what are nanoparticles and liposomes?

A

advanced systems that deliver drugs at cellular level for targeted therapy (e.g via intravenous injections)

27
Q

pipeline of generating medicines

A
  1. drug discovery
  2. preclinical studies = screens of lots of drug molecules, identify the ones that have wanted biological effect to make them into a medicine
  3. clinical studies = prone to failure
  4. FDA regulatory approval
  5. postmarketing monitoring
28
Q

clinical studies

A
  • phase 1 : see if drug is safe for healthy people
  • phase 2: see if drug is safe for people with condition + how much it helps their symptoms
  • phase 3: see if treatment is better than what we already have (comparisons)

then new drug application can be put in.

29
Q

drug discovery and pre clinical development

A
  1. target identification and validation (target drug to have desired therapeutic effect)
  2. drug screening (find out if drug actually binds to the target or not)
  3. lead optimisation = drug synthesis (drug needs to have combination of safety, solubility, ability to be absorbed, metabolic stability)
  4. formulation development = pre-form, formulation design and manufacture, disintegration, stability testing)
  5. pharmacokinetics and toxicity
30
Q

what can formulation and drug delivery technology optimise?

A

the therapeutic effects of the drug as you could have a good drug but it is useless if it can’t reach its site. oral delivery is not always suitable

31
Q

describe drug absorption if there is no enteric coating on the drug

A
  • dosage form swallowed and then can start dissolving and releasing the drug in the stomach and then it passes into intestine
32
Q

describe drug absorption in the GI tract when the drug has an enteric coating that prevents it from being dissolved in the stomach

A

drug passes into the small intestine to the ascending colon to the transverse colon to the descending colon to rectum

33
Q

describe the blood supply to the intestine

A

mesenteric veins that coat intestine take all the blood that has absorbed the contents of intestine and empty the blood into the portal vein

34
Q

what does the small intestine and ascending colon empty blood into?

A

superior mesenteric vein

35
Q

what does the transverse and descending colon empty blood into?

A

inferior mesenteric vein

36
Q

the mesenteric veins go into the portal veins. what does the portal vein go into?

A

the liver (major site of detoxification, where drugs are metabolised)

37
Q

after the liver where does the blood go?

A

the heart and then into the systemic circulation. when its in the circulation the blood will diffuse into the tissues of the body to have intended biological effect at intended site

38
Q

what has to happen to a solid dosage form for it to be absorbed in the GI tract?

A
  • break apart
  • drug needs to go into solution
  • as human body cannot absorb solids
  • particles of dosage form which dissolve to form solution
  • drug is then absorbed across epithelium of GI tract
  • then into underlying blood
  • which then empties into the liver
39
Q

what effects the uptake of drugs in the GI tract?

A
  1. digestive enzymes to break down complex molecules into small ones which can be absorbed
  2. bacterial enzymes which metabolise drugs
  3. changes in pH which affect ionisation and absorption
  4. prescence of food which acts as physical barrier and makes contents of GI tract more viscous, decreasing diffusion of drug across epithelium. drug molecules can interact with components of food stopping them from being absorbed
  5. first line of defence in body is a barrier. stomach acid. efflux pumps in GI tract that protect body from toxic molecules, they will pump drug back out of the cells of the epithelium
  6. metabolic enzymes at tips of villi. metabolise and activate drug.
  7. villi and microvilli on epithelium that increase surface area
  8. drugs have h bonds that need to be broken to be absorbed across memb
  9. bigger drug = slower diffusion
40
Q

describe the para cellular pathway in which drugs can pass

A
  • between cells
  • very restricted due to tight spaces between cells
  • makes it harder for molecules to pass through
  • minor way
  • transporters in gi tract. if drug is similar shape to substrate of a transporter it may be absorbed
41
Q

effects of pH on drugs

A
  • acidic pH in stomach
  • neutral pH in GI tract
  • most drugs are weak acids or bases
  • so changes in pH changes ionisation of drugs
  • drugs need to be unionised for optimum absorption
42
Q

effects of lipophilicity (dissolving in non polar solvents)

A
  • drug needs to have some liphophilicity to get into membrane
  • but not too lipophilic that it can’t get back out of membrane
  • balance between hydrophobicity and philicity
43
Q

what is pharmaceutics?

A

science of making drugs

44
Q
A
45
Q
A
46
Q

what is biopharmaceutics?

A

study of the interaction of the medicine (the physical, physicochemical properties of the drug, the delivery system, components of the delivery system and site of delivery) with the biological system to optimise the drug delivery system (DDS)

47
Q

what is the bioavailability of a drug?

A

a measure of the quantity of drug which is absorbed and reaches its site of action and the rate at which it gets there

48
Q

equation for the overall net bioavailability of drug via oral delivery

A

F = Fa x Fg x Fh

Fa= fraction absorbed
Fg = fraction escaping GI metabolism
Fh = fraction escaping hepatic metabolism (liver)
F= fraction that gets into systemic circulation (net oral availability)

49
Q

why may a drug in a medicine not be the API?

A
  • ## some metabolites may be more active than the parent drug
50
Q
A

SL12102 - the science of medicines (5 decks)

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