Lecture 4 Modified Release Flashcards
What does MEC stand for?
median effective concentration
What does MTC stand for?
median toxic concentration
The large the distance between the MEC and the MTC, the greater safety of the drug. T/F
True
What are the advantages of modified-release dosage forms?
less fluctuation in blood levels, reduced dosing frequency, enhanced convenience and compliance, reduce adverse side effects, and overall reduction in health care costs (due to enhanced compliance).
What are the disadvantages of modified-release dosage forms?
Potential that all of drug may be released at once, may not be an option for some populations, takes longer to clear out of system, not enough variation available, can not crush.
What makes a good candidate for modified release products?
They exhibit neither very slow nor very fast rates of absorption and excretion. (too fast - huge tablet, too slow - doesn’t need modified release)They are uniformly absorbed from the GI tractThey are administered in relatively small dosesThey process a good margin safetyThey are used in the treatment of chronic rather than acute diseases. (the need to adjust in acute disease makes modified-release dosage forms unpractical)
What are the important variables relevant to modified release formulation?
route of drug administration, type of delivery system, disease being treated, patient, length of therapy, drug properties(biological properties ADME, solubility permeability)
What is a modified-release form
Release features based on time, course, and/or location that are designed to accomplish therapeutic or convenience objectives not offered by conventional or immediate-release forms.
What is an extended-release form?
Reduced frequency of dosage
What is a delayed-release form?
Releases the drug from the dosage from at a time other than promptly after administration.
What is a repeat action form?
Usually contain two single doses of medication, one for immediate release and the second for delayed release.
What are different types of extended-release forms?
Delayed release, repeat action, and targeted release(might not be extended).
What is a targeted-release form?
Directed toward isolating or concentrating a drug in a body region, tissue, or site for absorption or for drug action.
How can you control drug release through dissolution?
By controlling access of biologic fluids to the drug through the use of barrier coatings.
How can you control drug release through diffusion rates?
Reservoir devices - drug release is governed by Fick’s first law of diffusionMatrix devices - Pseudo steady(state is maintained during release) and release medium is perfect sink at all times.
How can you control drug release through chemical reactions?
Chemical reaction or interaction between the drug substance or its pharmaceutical barrier and site-specific biological fluids.
What are the three ways you can control drug release?
Dissolution, Diffusion, and chemical reactions
How can drug release be controlled using coated beads, granules, or microspheres?
Variation in coat thickness affect rate at which fluids can penetrate the coating to dissolve the drug.
How can multitablet systems be used to control drug release?
Small spherical compressed tablets with varying drug release characteristics can be placed within gelatin capsule shells.
What is microencapsulation?
Process of enclosing solids, liquids, or gasses within microscopic particles by forming thin coatings of wall material around the substance.
How does embedding a drug in slowly eroding or hydrophilic matric system affect drug release?
Drug substance is combined and made into granules with an excipient material that slowly erodes in body fluids, progressively releasing the drug for absorption.
How does embedding drug in inert plastic matrix affect drug release?
Drug is granulated with an inert plastic material and the granulation is compressed into tablets; drug is slowly released from the matrix by diffusion.
What is a complex formation?
Chemical combination of drug substance with other agents to form complexes that may be only soluble in body fluid, depending on the pH of the environment.
What is an ion-exchange resin?
Resin-drug complex is prepared and may be tableted, encapsulated or suspended in aqueous vehicle. Drug release depends on pH and electrolyte concentration in the GI tract.
What is an osmotic pump?
System composed of a core tablet surrounded by a semi-permeable membrane coating having a 0.4 mm diameter laser-produced hole through which drug is released by osmotic pressure.
What are types of coating materials used in modified dosage forms?
Don’t memorize just be familiar with these!Hydroxypropyl methylcelluose, methylhydroxy ethylcellulose, ethylcellulose, polyvinylpyrrolidone(PVP), sodium carboxymethylcellulose, polyethylene glycols.
What are enteric coating materials?
Cellulose Acetate Phthalate (CAP) and Eudragits
What should patients be advised of when using modified dosage forms?
Dose and dosing frequency, don’t use them interchangeably with IR, do not crush or chew, NG an PE tube patients, Nonedible plastic matrix shells and osmotic tablets remain intact in the stool.
