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PHRM 100 – PDD > PDD 14 and 15: Solid Oral Modified Dosage Forms > Flashcards

PDD 14 and 15: Solid Oral Modified Dosage Forms Flashcards

1
Q

What are the types of oral modified-release forms?

A
  • delayed release
  • extended release
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2
Q

What is delayed release?

A

dosage form allows a reduction in dosing frequency

  • enteric coating to prevent drug release in stomach
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3
Q

What is extended release?

A

dosage form designed to release the drug at a time other than promptly after administration

  • maintain optimal drug concentration in blood over a period of time
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4
Q

What are the advantages of extended-release pharmaceuticals? (2)

A
  • reduce dosing frequency
  • eliminate the need for night dosing
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5
Q

What are the disadvantages of extended-release pharmaceuticals? (2)

A
  • loss of flexibility in adjusting the dose
  • risk of dose dumping
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6
Q

What is repeat action?

A

tablet contains the immediate-release dose in the shell or coating, and the second dose in the inner core, separated by a slowly permeable barrier coating

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7
Q

What is targeted release?

A

dosage form releases the drug at a specified site (ie. pH sensitive and microflora sensitive)

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8
Q

What are the characteristics of drug candidates for extended-release products? (6)

A
  • do not exhibit very slow rates of absorption
  • do not exhibit very fast nor very slow rates of excretion (t1/2 need to be > 2h, but < 8 h)
  • uniformly absorbed from the gastrointestinal tract
  • administered in relatively small doses
  • possess a good margin of safety
  • used in the treatment of chronic conditions
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9
Q

How are extended-release technologies generally achieved?

A

by modifying the drug release rate or slowing the transit time of the dosage forms thorough the GI tract

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10
Q

What are the 3 major mechanisms of extended-release technologies?

A
  • modify drug dissolution by using barrier coatings
  • control drug diffusion rates from dosage forms
  • chemical reaction or interaction between the drug substance or its pharmaceutical barrier and site-specific biological fluids
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11
Q

Case Study 1: Coated Beads, Granules, and Microspheres

What are granules coated with?

A

materials like beewax, glyceryl monostearate, cetyl alcohol or ethylcellulose with different thicknesses

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12
Q

Case Study 1: Coated Beads, Granules, and Microspheres

What are granules formulated into?

A

blended and formulated into a capsule or tablet

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13
Q

Case Study 1: Coated Beads, Granules, and Microspheres

What does the coating thickness of granules determine?

A

the fluid penetration rate into the granules, and ultimately the drug dissolution rate

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14
Q

Case Study 2: Multitablet System

What is a multitablet system?

A
  • each capsule contains 8-10 minitablets (3-4 mm)
  • some minitablets are coated for extended release, and some are uncoated for immediate release
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15
Q

Case Study 3: Microencapsulated Drug

A
  • drug is encapsulated in gelatin-acacia droplets, followed by drying and filling into a capsule
  • drug release rate is determined by the ratio of core to wall, and the polymer used for microencapsulation
  • other polymers: polyvunyl alcohol, ethylcellulose, polyvinyl chloride
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16
Q

Case Study 4: Embedding Drug in Slowly Eroding or Hydrophilic Matrix System

A
  • drug is mixed with hydroxymethylcellulose (HPMC) (generally 20%) and made into a tablet
  • after ingestion, the tablet is wetted by fluid, and HPMC begins to hydrate, forming a gel layer for soluble drug to release (diffusion dependent) – polymer must form a gel layer rapidly to protect the tablet from rapid disintegration
  • the gel layer will erode overtime allowing insoluble drug to release (erosion dependent)
17
Q

Tablet Disintegration vs. Tablet Erosion

A
  • disintegration: immediate release
  • erosion: extended release
18
Q

Case Study 5: Embedding Drug in Inert Plastic Matrix

A
  • drug is granulated with an inert plastic material such as polyethylene, polyvinyl acetate, or polymethacrylate, and the granulation is compressed into tablets
  • drug is slowly released from the inert plastic matrix by diffusion
  • inert tablet matrix, expended of drug, is excreted with the feces
19
Q

Case Study 6: Complex Formation

A
  • certain drugs form chemical complexes with other agents, resulting in reduced dissolution in body fluids
  • salts of tannic acid (tannates) provide this quality in a variety of proprietary produces by the trade name Rynatan
  • tannic acid can complex with positively charged drugs (weak base) such as brompheniramine maleate (antihistamine)
  • complex formation reduces the solubility and therefore, sustains the drug release
20
Q

Case Study 7: Ion-Exchange Resin

A
  • resin-drug complex may be tableted, encapsulated, or suspended in an aqueous vehicle
  • drug release is dependent on the pH and the electrolyte concentration in the gastrointestinal tract
21
Q

Case Study 8: Osmotic Pump

What is the OROS system (Alza)?

A

core tablet surrounded by a semipermeable membrane coating having a 0.4-mm-diameter hole

  • core tablet contains a drug reservoir layer and a polymeric osmotic layer
  • after swallowed, water enters into the core tablet, dissolving or suspending the drug
  • as the pressure increases in the osmotic layer, it expands and pushes drug solution out
  • release is driven by the osmotic gradient
22
Q

Case Study 9: Repeat-Action Tablet

A

tablet contains the immediate-release dose in the shell or coating, and the second dose in the inner core, separated by a slowly permeable barrier coating

  • design will generally allow the drug release from the inner core 4-6 h after the administration
23
Q

Why might the release of a drug from an oral dosage form be intentionally delayed until it reaches the intestines? (3)

A
  • to protect a drug from being destroyed by gastric fluids
  • to reduce gastric distress caused by drugs particularly irritating to the stomach
  • to facilitate GI transit for drugs which are better absorbed from the intestines
24
Q

What are enteric coated capsules and tablets?

A

specially coated to remain intact in the stomach and to yield their ingredients in the intestines

25
Q

What might enteric coating be dependent on?

A
  • pH dependent, breaking down in the less acidic environment of the intestine
  • time dependent, eroding by moisture over time during gastrointestinal transit
  • enzyme dependent, deteriorating as a result of the hydrolysis-catalyzing action of intestinal enzymes
26
Q

What agents may be used for enteric coating of tablets and capsules?

A

fats, fatty acids, waxes, shellac, and cellulose acetate phthalate

27
Q

What are the advantages of extended-release dosage forms over conventional forms?

A
  • reduction in drug blood level fluctuations
  • frequency reduction in dosing
  • enhanced patient convenience and compliance
  • reduction in adverse side effects
  • reduction in overall health care costs
28
Q

What are the features of the OROS?

A
  • drug release rate is constant as long as the osmotic gradient remains constant
  • drug release rate can be altered by changing the surface area, thickness and composition of the semipermeable membrane, and the diameter of the drug-release orifice
  • drug release rate is not affected by pH and fed conditions
  • tablet is eliminated in the feces as an insoluble shel
29
Q

Describe the specifics of labelling modified-release pharmaceuticals.

A
  • label of aspirin delayed-release tablets must state that the tablets are enteric coated
  • label for theophylline extended-release capsules must indicate whether the product is intended for dosing every 12-14 h and state with which in vitro drug release test the product complies
30
Q

What are some clinical considerations in the use of oral modified-release dosage forms?

A
  • patients should be advised of the dose and dosing frequency of modified drug release products and instructed not to use them interchangeably or concomitantly with immediate-release forms of the same drug
  • patients stabilized on a modified-release product should not be changed to an immediate-release product without considering any existing drug in the blood – they should not be changed to another extended-release product unless there is assurance of equivalent bioavailability
  • patients should be advised that modified-release tablets and capsules should not be crushed or chewed since such action would compromise their drug release features
  • patients and caregivers should be advised that non-erodible plastic matrix shells and osmotic tablets remain intact throughout GI transit and the empty shells from osmotic tablets may be seen in the stool

PHRM 100 – PDD (14 decks)

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