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Block 1.12 > Dosage forms and P&P affecting absorption > Flashcards

Dosage forms and P&P affecting absorption Flashcards

1
Q

What is pharmaceutics?

A

Science of dosage form design

Dosage form = interface between drug and body

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2
Q

What is the purpose of having dosage forms?

A

To safely and conveniently provide accurate dosage (different routes, ER)

protect the drug from destructive effect of storage environment (Oxidation, humidity, light)

protect drug from body after taking it (pH of stomach, use enteric coated tabs or caps)

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3
Q

What are the components in a dosage form?

A

Active ingredients

The component(s) that are intended to have pharmacological action

Excipients

Not included to have pharm action

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4
Q

What are some of the excipients used and whats their main purpose?

A

Organoleptic modifiers (things that affect the sense organs) will improve smell, taste, texture.

Stability enhancers Agents to mess with pH Antioxidants Antimicrobial and anti-fungal preservatives

Chelating agents (bind to trace metals (these will act as catalysts for rxn) and prevent oxidation from happening so it improves stability

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5
Q

What is the most common route of administration and what are the advantages or disadvantages?

A

PO: enteral, will give systemic effects

Advantages

Natural (dont need to do in office) simple and safe

Non invasive

Disadvantages

First pass metabolism

Slow drug response irregular absorption

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6
Q

What is parenteral route?

A

Its a type that avoids the GI tract its going to be injectables such as IV or IM It will get systemic circulation faster and be more bioavil

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7
Q

What are the advantages of parental route?

A
  1. IV is fast way to get response
  2. Avoids first pass so drug is not broken down in GI
  3. Can be good if pt is unresponsive or wont take pills
  4. Can deliver drug directly to site of action
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8
Q

What are some disadvantages of parental route?

A
  1. Once its given you cant take it back (if oral you can induce emesis before absorption takes place)
  2. More expensive to make
  3. Needs special training
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9
Q

What is the difference between topical and transdermal?

A

Topical is intended to be used locally at the site of the problem with no systemic absorption

transdermal is a patch that is put on and has the intention of systemic absorption into the blood stream

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10
Q

What is the route a PO drug takes? (also for IV and IM)

A
  1. enters the GI system
  2. Some will get excreted here but it will also be absorbed into the circulatory system
  3. More will be excreted from circulatory, but it will also go to the tissues or metabolic sites
  4. the metabolic sites will be for created drug metabolites and aid in excretion

**IV and IM are the same thing just depends where they are injected (IV starts in circulatory and then travels to these places)

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11
Q

What are the Physicochemical factors that effect drug absorption?

A
  1. Partition coefficient (degree of solubility)

Must be both lipo and hydro philic to get thro membrane

  1. Molecular weight (larger makes it harder to diffuse across)
  2. pH and pKa (degree of Ionization, if ionized it will not pass thro)
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12
Q

What is passive diffusion?

A

When a molecule passes thro a membrane

Always follows a concentration gradient from high to low

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13
Q

What is facilitated diffusion?

A

Its when a molecule goes thro a membrane but must use a protein/carrier to bring it across

Goes from high to low concentration

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14
Q

What is active transport?

A

When a molecule go thro a membrane using a protein

Goes against the gradient and it requires energy to pump it across. (ATP)

EX. efflux proteins

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15
Q

What effects the kinetics of diffusion?

A
  1. Larger molecules move across slower than smaller ones
  2. Ions move much slower than molecules that have balance of lipo and hydro philictiy
  3. Also depends on the thickness of the membrane (Thinker = longer to move across)
  4. The concentration of the molecules also plays a role (if you have a larger difference you will get quicker transfusion)
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16
Q

What is saturation kinetics and how does it effect membrane transport?

A

in facilitated transport you can only bind so many molecules to the transporter.

Once you bind all the sites its “saturated” meaning you can no longer move the molecule across

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17
Q

Can non-ionized (uncharged) or ionized (charged) molecules move across the membrane?

A

The uncharged (unionized) can diffuse across membranes while the charged (ionized) can not

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18
Q

How does the Hydrophilicity of a drug effect its ability to pass?

A

Gives it aqueous solubility IT MUST BE IN SOLUTION to be absorbed

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19
Q

How does the lipophilicity of a drug effect its ability to pass?

A

affects how well a drug can dross a lipid membrane via passive transport

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20
Q

What is the partition coefficient?

A

Its how we determine how hydrophilic and lipophilic a compound is.

P = Concentration in oil / concentration in water

EX: you have a drug conc in oil of 300 mg/ml and its conc in water is 100 mg/ml. what is the partition coefficient? it would be 300/100 = 3

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21
Q

What does it mean is the PC (partition coefficient) is greater than 1 PC>1?

A

It means the drug would be more lipophilic

*soluble in oil

**** Log P > 0

22
Q

What does it mean is the PC (partition coefficient) is less than 1 PC<1?

A

It would mean that the drug is more hydrophilic

*soluble in water

*****Log P < 0

23
Q

Explain why you look at log values and how it can relate to the ratio of lipo vs hydro

A

logP of 0 = P will be 1

log P of 1 = P will be 10

log P of 2 = P will be 100

log p of 3 = P will be 1000

This allows you to see a ratio of how the log relates to the lipo or hydro of a drug. If you have a log P valve of 3.75 it would mean that the drug is almost 10,000 times more lipophilic

24
Q

How is the PC (partition coefficient) relate to how well a drug will be absorbed?

A
  1. Very hydrophilic (lower PC) drugs will not partition well into bio membranes
  2. Very lipophilic (high PC) will not be soluble in water and unable to be absorbed

This means you MUST have a good mix between the both in order to be absorbed. Meaning the absorption vs increasing lipohilicity (inc of PC) graph will be parabolic

25
Q

What is Lipinski’s “Rule of 5”?

A

A chemical candidate is likely to display poor absorption if

  1. More than 5 hydrogen bond donors
  2. More than 10 hydrogen bond acceptors
  3. Molecular weight > 500
  4. Log PC > 5

**companies use this to see if a drug they create will even be viable to be absorbed. If you have any of these things it will not likely be absorbed

26
Q

What is a Bronsted Lowry Acid?

A

Any substance, charged or uncharged that is capable of DONATING a proton

27
Q

What is a Bronsted Lowry Base?

A

Any substance, charged or uncharged that is capable of ACCEPTING a proton

28
Q

What does a drugs degree of ionization depend on?

A

The pKa (value of pH where 50% is ionized and unionized) and the pH of its surroundings

** Weak acid = mostly uncharged at low pH (unionized, will be absorbed)

**Weak Base = mostly uncharged at high pH (unionized, will be absorbed)

*****think of how the graphs are set up

29
Q

What is the Henderson-Hasselbalch Equation for a weak acid?

A

pH = pKa + log (ionized / Unionized)

**KNOW THESE!!!! IOU and acid

30
Q

What is the Henderson-Hasselbalch Equation for a weak base?

A

pH = pKa + log (Unionized / ionized)

31
Q

Whats the avg pH in the stomach?

A

It will be low around 1-3

32
Q

Whats the avg pH in the duodenum?

A

It will be around 5-7

33
Q

What is the avg pH of the jejunum?

A

6.5

34
Q

What is the avg pH of the ascending colon?

A

7-8

35
Q

Can the ionized form of a weak acid/base cross a membrane?

A

NO!!!!

they are more water-soluble when ionized which makes it very difficult to cross a membrane!

36
Q

Can the unionized form of a weak acid/base cross a membrane?

A

YES!!

They are more lipid-soluble so they can cross the membranes easier than the ionized form

37
Q

What is disintegration of a drug?

A

Its when the solid drug product disintegrates into smaller particles

*not the rate limiting step unless its a controlled release drug

38
Q

What is dissolution of a drug product?

A

Its going to be how well the drug dissolves into solution

This is often controlled by the size of the drug

The smaller the particle or drug the quicker it will go into solution

39
Q

If you increase the particle size how will it effect the dissolution rate?

A

It will decrease meaning it takes longer for it to go into solution (longer to be absorbed)

40
Q

If you increase the surface area of a particle, how will it effect the dissolution rate?

A

It will increase it ( quicker into solution meaning quicker absorption) If you increase SA it means you have more places to effect the particle meaning you can quickly get it broken up and absorbed

41
Q

How does the crystal form effect dissolution?

A

An unstable polymorph (dissolves quicker) usually exhibits a greater dissolution rate than a stable one

***Amorphous solid (doesnt have a real shape) will dissolve more rapidly than other types of crystalline forms

42
Q

What is gastric emptying?

A

Can take 5 min to 2 hrs

Its the time a drug spends in the stomach before emptied into the small intestine

***a delay in GET affects drug absorption

43
Q

What are some things that effect gastric emptying?

A
  1. Fasted is faster than fed state (You will absorb quicker if you are in a fasted state over a fed state)
  2. Meal size (larger meal = slower absorption rate)
  3. High fat meals = delay GE (slow absorption)
  4. Drugs delay it ( anticholinergics (can be used for diarrhea)
  5. Can speed it up with drugs ( cholinergic drugs) 6. formulation of drugs effect how quickly (Liquids < digested solids < larger solids )
44
Q

What is the absorption window?

A

This is the area within the GI tract where a drug is most efficiently absorbed

**must stay in this window for a long enough time in order for it to be absorbed correctly

45
Q

What is the small intestinal transit? Does it matter if you are in a fed or fasted state?

A

This is a relatively constant time (3-4 hours)

**if you decrease the intestinal transit time (have diarrhea or drug to increase GI motility) the drug absorption will DECREASE

*****DOES NOT MATTER if in fed or fasted or liquids or solids

46
Q

What is colonic transit?

A

Not usually a good place for drug absorption

Long and variable (2 to 48 hrs)

big spot for water and electrolyte re absorption

47
Q

How does Perfusion of the GI tract effect absorption?

A

When you have decreased GI perfusion ( CHF ) it will decrease the amt of blood to the area which will decrease the rate of drug removal from the intestinal tract which will reduce the absorption rate

48
Q

Explain these two graphs

A
  1. For a weak acid membrane permabily is affected by if it ionized or unionized. At low pH a weak acid will be unionized meaning that it will have a higer membrane permabilty. as you increase the pH you will also increase a weak acids ionization which will decrease its membrane periability
  2. A weak base will be more UNIONIZED at a higher pH (there is nothing that will donate to it) meaning and at lower pH it will be more ionized
49
Q

Explain these graphs

A
  1. For a weak base as the pH increases you will be increased its unionization which means it will be more LIPOPHILIC meaning its PC will be greater than 1.

** at low pH it will be more ionized (soluble in water) making it hydrophilic meaning it will have a lower PC valve

***A weak acid would be the exact opposite of this. At low pH it would be unionized making it lipophic and having a high PC value (better for absorbtion) and at a higher pH it will be ionized (lower PC) and by hydrophilic

  1. The more carbons you add will increase the PC value.

*** remember there is a sweet spot for PC value and the higher you get is not always good

50
Q

Explain these graphs

A
  1. The larger the particle the lower the dissolution rate

**larger particles take a longer time to break down meaning it will take longer to get into solution so it can be absorped

  1. At low pH an weak acid will be unionized meaning it will be more soluble in water and can be absorbed. at higher pH it will be ionized meaning it will be less water soluble and will not be absorbed as well
51
Q

How does food affect drug absorption?

A

Having food in your stomach will affect gastric empyting. If you have food it will slow down absorbtion making it take longer

Block 1.12 (5 decks)

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