Novel drug delivery and drug targeting

Question 1

What are the possible problems with conventional drug formulations?

Answer 1

Drugs with short half life which require frequent dose and fluctuations in blood concentration
Some drugs are highly toxic

Question 2

Why are new drug delivery formulations and techniques?

Answer 2

Financial gain
to control rate of drug delivery
to sustain the duration of therapeutic activity
To target drug to specific tissue/site
These allow optimization of drug exposure to the the site of action

Question 3

What are the advantages of sustain release formulations?

Answer 3

There are reduced peak-trough fluctuations reducing the chances of adverse effects associated with high peaks and no effect with trough conc
The frequency of administration can be reduced which is good as compliance can start to become a problem if there is more than two administrations a day required

Question 4

How can various coatings used on drugs to produce a sustained release formulation?

Answer 4

There are enteric coatings which are resistant to pH ad dissolve in the small intestine
Capsules which have active drug beads but are different thicknesses so the drug is released at different time intervals

Question 5

How can matrix tablets result in a controlled release formulation of a drug?

Answer 5

The tablet can contain an insoluble polymer which results in the drug being released by leaching and diffusion
Swelling or gelling tablets contain hydrophobic polymers which forms an outer gel layer which controls the release of the drug via erosion and diffusion

Question 6

How can osmotic devices be used to produce a sustained release drug formulation?

Answer 6

An osmotically active drug core is coated with a semi-permeable polymer which allows exit out of a small hole using H2O influx to pump out the drug

Question 7

How can bioadhesives and floating devices be used to produce a sustained release drug formulation?

Answer 7

An adhesive polymer can be used to adhere to the mucin which covers the GI tract
Floating devices can float on gastric contents and are therefore retained longer in the stomach

Question 8

What are examples of drugs that use osmotic drug delivery tablets?

Answer 8

Methylphenidate
Verapamil
Nifedipne

Question 9

What are the factors that control the GI transit of drugs?

Answer 9

Feeding state
Size of the object as objects less than 10mm can empty from the fed stomach while objects greater than 20 mm will be retained
Transit time in the small intestine is 3 hours
A dosage form can reach the colon in 4-5 hours in fasted subjects
Transit time in the colon is lengthy