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Pharmacy > Science of Medicines Week 11 > Flashcards

Science of Medicines Week 11 Flashcards

1
Q
A
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2
Q

What are examples of diseases treated by topical delivery to the mouth?

A

ulcers, fungal infections, periodontal disease

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3
Q

What is different about oral dosage forms and dosage forms that cross membranes in the mouth?

A

crossing membranes in the mouth allows them to bypass the GI tract, so they avoid hepatic first-pass

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4
Q

define sublingual

A

under the tongue

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5
Q

define buccal

A

via the epithelia that line the cheek

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6
Q

What is the name given to the lining of the mouth?

A

the oral mucosa

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7
Q

What is the structure of the oral mucosa?

A
  1. squamous epithlial cells
  2. layers of basal, intermediate, superficial cells
  3. lipophilic membrane-coating cells
  4. lamin propia underneath basement membrane contains blood vessels, so it where drug must reach
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8
Q

How do drugs absorb via the transcellular pathway in the oral epithelia?

A
  1. good for small, lipophilic drugs
  2. occurs by passive diffusion
  3. depends on epithelial thickness
  4. rate of absorption is therefore determined by Fick’s 1st law
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9
Q

How do drugs absorb via the paracellular pathway in the oral epithelia?

A
  1. good for small, hydrophilic drugs
  2. involved intracellular lipid molecules (MCGs) from the membrane-coating granules
  3. also depends on epithelial thickness
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10
Q

What are the 2 main factors affecting drug absorption in the mouth?

A

saliva and mucus, blood supply to the mouth

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11
Q

How does saliva affect drug absorption via the mouth?

A
  1. aids absorption by solubilising drug, but can hinder it by saliva washout
  2. enzymes in the mouth may break down drugs
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12
Q

How does mucus affect drug absorption via the mouth?

A

it is a physical AND chemical barrier as it is thick

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13
Q

How does blood supply affect drug absorption via the mouth?

A
  1. very good blood flow which is good for absorption
  2. avoids hepatic first pass metabolism
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14
Q

What are the advantages of buccal and sublingual drug absorption?

A
  1. rich blood supply
  2. avoids hepatic first-pass
  3. low metabolism
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15
Q

What are the disadvantages of buccal and sublingual drug absorption?

A
  1. high MW drugs must be potent
  2. saliva and mucus can impact absorption
  3. development costs
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16
Q

give examples of patients who the rectal route of drug administration would be beneficial for

A
  1. unconscious patients
  2. children
  3. vomiting
  4. upper GI tract disease
  5. drugs that are much degraded via oral delivery
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17
Q

What are examples of rectal dosage forms?

A

tablet, capsules, suppositories, ointments, creams, gels, solution, emulsions, suspension

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18
Q

What is the structure of the rectum?

A
  1. makes up last part of the colon
  2. upper and lower regions
  3. no villi
  4. normally empty
  5. small amount of mucus
  6. epithelium is one cell thick
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19
Q

What are the two routes of drug absorption in the rectum?

A

transcellular and paracellular - MOSTLY transcellular

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20
Q

How is the rectal route a possible route for protein delivery?

A

there is no esterase or peptidase activity

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21
Q

Why must you be cautious on where in the rectum a drug is administered?

A
  1. blood vessels may reach systemic circulation in upper region
  2. superior vein in upper region will empty into hepatic portal vein -> hepatic first pass
  3. inferior and middle veins go into systemic circulation in lower region, so avoid this
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22
Q

Why is diazepam gel administered rectally?

A
  1. it is highly metabolised to desmethyldiazepam in the liver by CYP450 enzymes
  2. this is an active metabolite
  3. avoids metabolism and is used to manage seizures in refractory epileptic patients
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23
Q

What are the advantages of rectal administration?

A
  1. avoids degradation in GI tract
  2. avoids hepatic first pass
  3. potential for extended absorption
  4. good alternative when oral delivery is not possible
  5. potential for protein delivery!
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24
Q

define enteral

A

via the intestine, opposite to parenteral

25
Q

define parenteral

A

anything administered other than through the digestive tract e.g injections

26
Q

define ‘other routes’

A

delivery directly to a site of action for a localised effect e.g. topical

27
Q

intradermal injection

A

into the epidermis

28
Q

intramuscular injection

A

into the muscle

29
Q

intravenous injection

A

into the vein

30
Q

subcutaneous injection

A

into the subcutaneous tissue

31
Q

intramedullary injection

A

into the bone marrow

32
Q

What are the advantages of intravenous drug delivery?

A
  1. drug administered to site of action rapidly
  2. precise dosing
  3. 100% ‘bioavailability’
33
Q

What are the disadvantages of intravenous drug delivery?

A
  1. needs suitable vein
  2. professional is required
  3. higher cost
  4. potential toxicity as concentration rises very quickly
34
Q

How are drugs administered by subcutaneous injection?

A

drug passively diffuses into the capillaries or lymphatics

35
Q

What are the advantages of subcutaneous delivery?

A
  1. slow and sustained
  2. self-administration is possible
  3. implants can give long-term delivery
36
Q

What are the disadvantages of subcutaneous drug delivery?

A
  1. small doses must be used
  2. irritation from repeated injections
37
Q

What is nasal drug delivery used for?

A

topical treatment for allergies, congestion and infection

38
Q

Why is nasal drug delivery better than oral?

A
  1. avoids hepatic first pass
  2. the drug may be sensitive to enzymes
  3. acid-sensitive drugs
  4. poor oral absorption if a polar compound
39
Q

What is the structure of the nasal epithelium?

A
  1. microvilli so large SA
  2. protective layer of mucus and cilia
  3. a pseudo-stratified epithelium
40
Q

Why is the olfactory region a good potential target for drug delivery?

A

it is an area where the blood brain barrier is not present, so the drug can go straight from the olfactory region to the brain

41
Q

How can drugs enter the brain from the olfactory region?

A

by paracellular diffusion or axonal transport through the olfactory nerves

42
Q

What is ocular drug delivery used for?

A

ONLY for treatment of local conditions as NOT a goof route for systemic delivery

43
Q

What is used to treat diseases at the BACK of the eye?

A

intraocular delivery as it is very difficult to reach

44
Q

What is the main route of drug absorption at the front of the eye?

A

the corneal route -> either by paracellular or transcellular diffusion

45
Q

What is the conjunctival route?

A

when the drug passes through the conjunctiva and sclera, but most of the drug will be lost into the capillary bed and enter systemic circulation

46
Q

What are the issues associated with drugs delivered to the front of the eye?

A
  1. tear ducts allow a good drainage and defence system
  2. much of drug is lost to nasolacrimal drainage and goes down the back of the throat
47
Q

Which factors affect drug absorption in vaginal delivery?

A

pH

48
Q

When does pH in the vagina change?

A
  • with age
  • depending on time in the menstrual cycle
49
Q

Why does pH change during the menstrual cycle?

A

thick epithelium before menstruation with lots of glycogen, which is broken down into lactic acid

50
Q

Why is pH change in the vagina an issue?

A

the drug may be ionised, so it less likely to be absorbed over the membrane

51
Q

What are the issues with pulmonary drug delivery?

A

defence mechanisms clear waste

52
Q

What is the main issue with transdermal delivery?

A

the skin is a good barrier

53
Q

What is the main barrier in the skin?

A

the stratum corneum

54
Q

What is the structure of the stratum corneum?

A
  1. brick structure made of dead, flattened cells
  2. the inside of the membrane is protein-coated
  3. there are lipid rafts between cells making a lipophilic layer
55
Q

What are factors affecting transdermal drug absorption?

A
  1. hydration of the stratum corneum -> patches are occlusive so water builds up
  2. pH
  3. age -> babies and elderly have weaker skin
56
Q

What are two methods in increasing skin permeability for drug absorption?

A

iontophoresis and microneedles

57
Q

What is iontophoresis?

A

a device in which the electrical field increases the permeability of the skin, allowing molecules to be transported across the stratum corneum

58
Q

How do microneedles work?

A

they are inserted into the skin to create microchannels in the skin’s outermost layer, the stratum corneum, which allows for the transport of drugs and other substances

Pharmacy (16 decks)

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