Flashcards in Topic 2 Deck (16):
Why can glyceryl trinitrate be taken through transdermal administration
as it has oily preparations it can be absorbed through the skin from skin patches
What happens when the transdermal skin patch is applied
the glyceryl trinitrate is absorbed from the patches directly into the bloodstream through blood vessels in the skin and carried straight to its site of action in the heart, bypassing the liver.
Why is sublingual administration (tablet placed under the tongue) effective
as glyceryl trinitrate is well absorbed through blood vessels in the mouth
When would the sublingual method be used and why
for rapid pain relief and is useful when a person experiences sudden attacks, as absorption from the mouth is much more rapid than through the skin
When would the transdermal method be used
What determines the choice of a particular route of administration (incomplete)
1. Where possible, drugs are administered directly to their site of action. This provides a rapid onset of action, and usually produces fewer side effects s most of the drug reaches the desired target.
2. Where direct application is not possible or feasible, oral administration is utilised. In general, oral administration of a drug is safe, convenient and economical. For most people, it is easier to swallow a pill or syrup than to have an injection. For some drugs, however, there are some disadvantages, including: irritation (causing vomiting/discomfort), instability of drug in digestive tract, destruction by digestive enzymes, extensive first pass metabolism
3. Other routes of administration are used when: drug is not suitable, rapid effect required, person unconscious
4. Drugs are usually given by injection when oral administration is unsuitable
Forms of injection
intravenous injection; intramuscular injection; subcutaneous injection
produces an almost instantaneous effect as the drug is delivered directly into the bloodstream and carried to its site of action.
injection into muscle layers under the skin
injection is just below the skin
Which type of injection is quicker acting
intravenous as it is delivered directly into the bloodstream, while for intramuscular and subcutaneous injections, the drug is slowly absorbed into the blood vessels that supply skin and muscle
Which type of injection has a longer lasting effect
intramuscular and subcutaneous injections as while their absorption is slower, the effect is more long lasting compared to intravenous injection
What is the route of oral administration
1) drug is absorbed in the GI tract, passes through the liver and enters the bloodstream; 2) dose that reaches bloodstream can be reduced by digestion, liver (first pass) metabolism, vomiting/diarrhoea, contents of GI tract
What types of ways can drugs enter through different layers of the skin
intramuscular, subcutaneous or transdermal delivery methods.
What are the four basic stages in the life of a drug in the body (ADME)
absorption, distribution, metabolism, excretion