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PMY2006 Pharmaceutical Technology > Oral Biopharmaceutics > Flashcards

Oral Biopharmaceutics Flashcards

1
Q

Name the parenteral routes of adminstration?

A

Intramuscular - im
Intravenous - iv
Subcutaneous - sc

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2
Q

Name the enteral route of administration?

A

Oral
Rectal
Sublingual

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3
Q

Name the other routes of adminstration?

A

Transdermal
Ocular
Intranasal
Respiratory - inhalers

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4
Q

3 advantages of oral route?

A

Accepted by patients due to comfort and convenience.
Easy administration.
Prolonged and targeting release formulations available.

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5
Q

List the dosage forms via oral route?

A

Tablets, capsules, drops, liquid, suspensions, syrup, powders.

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6
Q

How are biological molecules such as proteins delivered?

A

IV or transdermal.

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7
Q

What are the 7 general steps to drug absorption?

A

Drug in drug product - disintegration of product - drug release into particles - dissolution of particles - solution of drug formed - absorption - drug absorbed into body.

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8
Q

Where does blood leaving GI lead to?

A

Blood leaving GI containing nutrients and blood drain to hepatic portal vein.

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9
Q

Describe first-pass metabolism?

A

When drugs with a high ‘first-pass effect’ are administered orally, a large amount of the absorbed drug is metabolised before it reaches the systemic circulation.

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10
Q

Describe the stomach.

A
  • acts as food reservoir
  • processes food into fluid chyme for absorption of nutrients by the small intestine
  • initiates digestion process
  • regulates delivery of food into the small intestine
  • produces acid which is bacteriostatic
  • stomach pH allows pepsin to function
  • is a non-absorptive surface due to smooth architecture
  • small surface area
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11
Q

Which drug molecule can be absorbed via stomach?

A

Aspirin

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12
Q

What is the effect of alcohol on drug molecules?

A

When drug is taken with alcohol, enteric coating will dissolve in stomach and drug will disintegrate into fine powder - more soluble - faster absorption.

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13
Q

What is gastrin and what is it stimulated by?

A

Gastrin is the potent stimulator of gastric acid production. Gastric production stimulated by peptides, amino acids and stomach distension.

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14
Q

Describe pepsin.

A

Pepsins are peptidases which breakdown proteins to peptides. They are secreted by peptic cells in precursor form, pepsinogen.
They are denatures above pH 5.

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15
Q

Describe mucus in stomach.

A

Secreted by mucosal cells, Goblet cells that line the gastric mucosa. Protects stomach from auto-digestion by pepsin-acid combination.

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16
Q

What are the factors affecting gastric emptying?

A

Volume of food/liquid (higher = higher emptying time)
Type of meal (protein, carbs - higher emptying, fats - lower emptying)
Drugs (opioids decrease emptying)
Physical state of contents (liquid and small solid particles - faster)
Others - stress, diabetes, pregnancy, body position

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17
Q

What is migrating myoelectric complex?

A

MMC are waves of activity that sweep through intestine in a regular cycle through a fasting state.

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18
Q

Where is the biggest absorption site?

A

Small intestine for nutrients, drugs and water.

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19
Q

Describe the characteristics of the small intestine.

A
  • long = 4-5m
  • high effective surface area (due to folds, microvilli and villi - maximizes absorption) and a large regional vasculature
  • major site for absorption of water, salts, nutrients, most orally administered drugs
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20
Q

What are the 3 parts of the small intestine called?

A

Functionally divided into

  • duodenum
  • jejunum
  • ileum
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21
Q

What are the 4 functions of the small inestine?

A
  1. mix the resulting chyme with enzymes to facilitate digestion.
  2. mix the intestinal contents with intestinal secretions to allow for absorption.
  3. to propel any absorbable contents in the aboral direction.
  4. water absorption
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22
Q

What are the small inestine sceretions?

A

Bile salts - emulsify fats and act as surfactants
Pancreatic enzymes - for digestion
Mucus - coats food, protects GI tract
Bicarbonate - in response to type of food, regulates pH

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23
Q

State the pH of the regions of small intestine.

A

pH duodenum 6 - 6.5
pH jejunum 6-7
pH ileum 7-8
pH in fed and fasted states may vary

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24
Q

Why do some drug formulations require to be taken before/after/with food?

A

Changes in small inestine pH has implications on MR tablets or enteric-coated tablets.
Defines pH is required to release drug from coating - dissolution of coating.

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25
Q

What does the large intestine consist of?

A

Caecum
Colon
Rectum

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26
Q

What are the 4 parts of the colon?

A

Ascending, transverse, descending, sigmoid.

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27
Q

What is pH of colon?

A

pH5.5-7.0

28
Q

What are the functions of the Colon?

A
  1. Limited absorption for drugs (no villi) but some good candidates for targeted and/or sustained release formulations (ulcerative colitis, e.g. mesalazine).
  2. Absorbs water (If 1.5L input into SI, 1.4L is absorbed by LI).
  3. Absorbs lipids: potential for lymphatic drug delivery.
  4. Bacteria (gut flora) metabolise some nutrients
29
Q

What is the transit time for large intestine?

A

6-10 hours or longer.

30
Q

What is the transit time for small intestine?

A

3-5 hours.

31
Q

What is the transit time for stomach?

A

2-3 hours.

32
Q

What is pH of rectum?

A

pH 7.

33
Q

Explain the draining of blood from the rectum?

A

Outgoing vein from the lower part of the rectum is the inferior hemoroidal vein. This drains into the vena cava as opposed to the portal vein (bypasses the liver), hence everything absorbed there is not subject to first pass effect.
(middle and superior hemaroidal veins still drain to portal vein)

34
Q

What are the functions of mucus?

A

Protects the epithelial cells and GI tract from chemicals/digestion/enzymes
Maintains pH gradient
Entraps particles
Reduces diffusion to mucosal surface

35
Q

How does food affect gastric emptying?

A 
Delay in gastric emptying - stomach
Stimulation in bile flow
Change of pH
Increase in splanchnic (GI tract, liver, spleen, pancreas) blood flow
Affects metabolism of the drug
Interaction of the food with the drug
36
Q

What is mesalamine/ 5-amino salicylic acid used for?

A

Treat inflammatory bowel disease.

Available as delayed release tablets - ASACOL.

37
Q

What is a polymer used to coat tablets for delayed-release?

A

Methacrylate copolymers

38
Q

Pentasa is another brand for mesalamine. Also used to treat inflammatory bowel diseases. This is a sustained-release formulation. Name some polymers used to coat these tablets.

A

Methyl acrylic acid
Cellulose acetate
Ethyl cellulose

39
Q

What is meant by physicochemical characteristics?

A

Physicochemical characteristics of drug molecules or drug particles are those that are related to the physiology of the gastrointestinal barriers.

40
Q

List 5 physicochemical properties of drugs?

A 
Solubility
Lipophilicity (LogP)
Dissolution
Charge
Particle size
41
Q

What are the 5 ways in which absorption occurs from the gut?

A
  1. Transcellular route via passive diffusion
  2. Transcellular route via active transport
  3. Transcellular route via facilitated diffusion
  4. Paracellular route through tight junctions of cells
  5. Particulate absorption via GALT - Gut-Associated Lymphatic Tissue)
42
Q

Describe the mechanism of the transcellular passive diffusion pathway.

A

There is high concentration on the apical side of the cell and low concentration inside the cell. The molecule will diffuse along the conc gradient through the cell and out into the intercellular area and blood.
(GIT-CELL-BLOOD)
- occurs with unionised molecules and lipophilic molecules.

43
Q

What is the partition coefficient?

A

A physicochemical constant which indicates the ability of a drug to move between phases, aqueous and lipid.

44
Q

What do positive and negative Log P values indicate?

A

Positive Log P = drug has higher affinity for lipid phase than aqueous phase.
Negative Log P = drug has high affinity for aqueous phase than lipid phase.
Log P should be in the middle to allow for passage through lipid and aqueous phases.

45
Q

Describe the mechanism of the transcellular active transport pathway.

A

This is a carrier-mediated pathway using transmembrane carrier proteins. Requires energy as molecules move against the conc gradient.
Energy comes from the hydrolysis of ATP or from the transmembranous sodium gradient or electrical potential.

46
Q

The two important characteristics of active transport are selectivity and competition. Explain these terms.

A

Selectivity - drug molecule will use a specific transporter protein.
Competition - two different drugs which are absorbed via the same transporter protein will compete for it and result in the reduced absorption of both.

47
Q

Describe the mechanism of transcellular facilitated diffusion pathway.

A

This is not an active process so no energy required.
Uses carrier transporter proteins. Requires a concentration gradient. The protein channels are structurally selective for specific drugs and so there will be competition for binding sites. The reaction will plateau is not enough carrier protein - saturated.

48
Q

Describe the mechanism of paracellular transport pathway.

A

Usually for hydrophilic/ionised drugs - can transport Ca2+ ions, sugars, amino acids and peptides (when conc above carriers)
Occurs by absorption between tight junctions/gaps of neighboring cells.
Concentration gradient dependent.

49
Q

Describe the mechanism of particulate absorption via Gut-Associated Lymphatic Tissue pathway.

Fact - mechanism can be utilised to make lipid based nanomedicines/ liposomal drugs.

A

Endocytosis via M (microfold) cells in the Peyer’s patches (found in the ileum) in the small intestine.
Plasma membrane of the cell invaginates and the invaginations become pinched off forming small intracellular vesicles.
Subsequent absorption into the lymphatic system.
Primary mechanism for macromolecules.

50
Q

How are CYP450 enzymes involved in self-protection of cells?

A

Subfamily CYP3A4 is involved in first-pass metabolism by the small intestine - metabolism of drug before it reaches systemic circulation.

51
Q

How are P-glycoproteins involved in self-protection of cells?

A

It is an efflux transporter protein involved in removal of toxic materials from the cell. Energy dependent mechanism, uses ATP.

52
Q

What is the effect of FPM in general?

A

Reduces amount of drug entering systemic circulation. Less bioavailability so higher doses of drugs must be administered.

53
Q

How can FMP effect be reduces/

A

Modify drug molecule into into prodrug.
Administer high doses of drug.
Combine drug with a CYP450 inhibitor.
Try another route of administration.

54
Q

What is the initial step of the dissolution process?

A

Disintegration

- the mechanical break up of a compressed tablet into small granules upon ingestion.

55
Q

What are superdisintegrants?

A
  • are disintegrating substances which are included in tablet formulations to aid in the break-up of the tablet into particles to allow dissolution/release of active ingredients.
56
Q

Name a few superdisintegrants and their key feature.

A 
Cross-linked cellulose.
Cross-linked alginic acid.
Cross-linked starch.
Cross-linked PVP.
- all are cross-linked to allow swelling to occur - they absorb water and swell - crack forms - breaks up tablet.
57
Q

What is dissolution?

A

Molecules become dispersed i.e. in solution before being absorbed across the gut via passive diffusion.

58
Q

What are the physicochemical properties of a drug which determines dissolution?

A

Solubility, particle size, wettability, polymorphs, crystalline character, pKa.

59
Q

What is solubility?

A

Solubility is a physicochemical property of the compound and corresponds to the maximum concentration that can be dissolved in the medium.
- weight of solute per volume of solvent.

60
Q

What are the factors which affect solubility, briefly describe these? (5)

A
  1. Polymorphism - arrangement of molecules within a crystal lattice.
  2. Temperature - increase in temp, increases solubility.
  3. pKa of drug and pH of medium - most drugs are weak acids/bases and have some ionisation.
  4. Particle size - smaller the particle size, higher surface area, increases solubility.
  5. Surfactants - e.g. bile salts increase solubility.
61
Q

Oral absorption of drug can be studied by In vivo Transit and site dependent absorption. How does this work?

A

By using a remote drug delivery capsule.
The capsule containing drug is remotely controlled. Releases drug at a specific time. Blood samples are collected.
Used to see how drug is absorbed in certain areas and if there are any side effects.

62
Q

Oral absorption can be studied by In vivo GI permeability studies. How does this work?

A

The tube is inserted releasing drug at a specific site. A segment is isolated by inflating balloons - prevents drug going any further. Blood measurements taken.
This study is crucial in those with bowel disease or inflammation.

63
Q

What is bioequivalence?

A

An extension of relative bioavailability for different formulations which involves comparing the total amounts of a particular drug absorbed intact from a test and recognised standard.

64
Q

When is a drug completely bioequivalent?

A

If there is no significant difference in pharmacokinetic parameters - Cmax, Tmax and AUC.

65
Q

Describe the 4 classes of BCS.

high solubility = drug dissolves in 250ml solvent or less

A

Class I - high solubility high permeability
Class II - low solubility high permeability
Class III - high solubility low permeability
Class IV - low solubility low permeability

PMY2006 Pharmaceutical Technology (10 decks)

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