Скачать или смотреть Modified Release Dosage Forms; brief lecture on modified release tablets: Simple and easy concepts

Products that have Drug release characteristics of time course and location chosen to accomplish therapeutic objectives not offered by conventional dosage forms like solution and immediate release tablets.
Modified release drug products are of three types
1. Extended Release Products: a dosage form that allows at least two fold reduction in in dosage frequency as compared to an immediate release drug product.
sustained release products, long acting products and controlled release are under this category.
ER, SR, XR, CD terms indicate extended release drug products.
2. Delayed Release products: a dosage form that releases drug or portions of drug at times other than promptly after administration.
The delay may be time based or pH dependent. e.g enteric coated tablets
3. Targeted Release Products: that release drug at or near the intended physiologic site of action. These may be immediate release or extended release.
Enetric coated tablets
Are the tablets that pass through stomach intact and disintegrate and release their content for absorption along the intestines.
Enteric coatings are designed to dissolve at pH 4.8 or greater.
For example enteric coated aspirin,
Materials used for enteric coating are
HPMC
cellulose acetate phthalate
metacrylate polymers
Shellac
Coatings are applied to either whole compressed tablet or granules used in fabrication of tablets or capsules.
Shellac is water insoluble at low pH and water soluble at higher pH
Repeat action tablets
It usually contains two single doses of medication, one for the immediate release and second one for delayed release.
Two layer tablets are prepared
the outer layer is formed by conventional immediate release formulation.
the inner core tablet having drug mixed with such excipients to dissolve after some time or provide the extended release pattern.
A sustained release drug product may be designed to deliver an initial therapeutic dose (loading doe) followed by a slower and constant release of drug. Extended release products are prepared by various techniques we shall discuss in next video but before that lets discuss its advantages to strengthen the idea y it is so needed and how it has revolutionized the science of formulation.

An example of this type of product is Repetabs.
Advantages of Extended Release Products
sustained therapeutic blood levels of the drug and consistent therapeutic response.
Unwanted side effects due to fluctuating blood levels of dugs may be avoided
Patient convenience which leads to better patient compliance
gives an economic benefit.
minimizes the toxicity.
maintains the efficacy over a longer duration
disadvantages
Oral administration of extended release products may yield erratic or variable drug absorption as a result of variation in GI content and pH at different sites.
2. If extended release contains more than two times the doses given it may be too large in size to swallow for the patient.
If enteric coating is poorly formulated it may be degraded in stomach resulting loss of drug action or irrtitaion to the stomach mucosa.
If enteric coating fail to dissolve upon reaching the proper site it may result in incomplete absorption.
Cost of drug may be higher than conventional dosage forms due to costly excipients needed for the formulation.
Dose dumping
defined as release of more that usual fraction of drug/greater rate of release than needed.
Such that potentially adverse plasma levels may be reached. As an example a dose dumping of theophylline is shown graphically you see Lower peak shows the desired sustained effect but the drug is somehow released all at once and concentration peaks so high. And striped area on the peak shows that the adverse effects like nausea vomiting and headache happened
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