Administration Of Drugs and Drug Handling by the Body Flashcards
(25 cards)
Which routes of absorption are most suitable for general anaesthetics?
Inhalation and intravenous
Which organ is the main site of absorption for orally administered drugs?
The small intestine
What do agonists do?
Bind to receptors and cause a response
What are the five cellular responses to drugs?
Contraction Secretion Excitation Inhibition Interruption of the cell cycle
Give an example of a drug that targets the membrane receptors
Salbutamol
Give an example of a drug that targets the ion channels
Local anaesthetic
Give an example of a drug that targets carrier molecules
Omeprazole
Give an example of a drug that targets enzymes
Aspirin
Give an example of a drug that targets the DNA
Steroids
Describe the the role of a second messenger in relaxing a smooth muscle cell
(Give examples of the drugs and enzymes involved)
- The drug (ie. Salbutamol) binds to the receptor
- The G protein is activated
- The activated G protein stimulates the second messenger (Aadenylyl Cyclase) to convert ATP to cyclic AMP
- Inactive protein 1 is converted to its active form
- Protein 2 is changed, which causes a loss of calcium ions from the cytoplasm
- Without the calcium the muscle relaxes
What are the routes of administration?
Oral (eg. Paracetamol tablets) Topical (eg. Hydrocortisone cream) Transdermal (HRT) Rectal (eg. Prednisolone) Inhalation (eg. Salbutamol)
Parenteral: intravenous (thiopental) intramuscular (pre-meds) intradermal (local anaesthetics) subcutaneous (insulin) intrathecal (chemotherapy drugs) epidural (nerve blockers)
Define the term bioavailability
The amount of drug that reaches the blood stream
What is the first pass metabolism?
The metabolism of the drug for the first time as it passes through the liver
What are the key targets for drug interactions?
Receptors Ion channels Carrier molecules Enzymes DNA
Microorganisms
How are drugs excreted?
In the urine In bile In faces Through the skin Exhalation
How can drug excretion be increased?
By increasing blood flow to the kidneys
By decreasing plasma protein binding
Describe Phase 1 in drug metabolism
The chemical structure of the drug is altered to make it slightly more water soluble
Describe Phase 2 in drug metabolism
The drug is conjugated to large molecules (ie. amino acids, sulphate groups) to increase their molecular weight
The metabolite is less chemically reactive
What is a pro-drug? (And give an example)
A drug that becomes more chemically reactive than the parent drug after phase 1 metabolism
eg. Prednisone becomes prednisolone
Codeine becomes morphine
How does metabolism affect liver enzymes?
Certain combinations of drugs can induce the liver enzymes, which metabolise the drugs, meaning they are in the bloodstream for a shorter time
eg. Alcohol and carbamazepine
Other substances can inhibit the enzymes so the drugs have a longer duration of action, meaning toxic levels can build up
eg. Grapefruit juice and Prozac
Where does drug metabolism take place?
Mainly in the SER of the liver
Also: Kidney Lung GI tract Brain Plasma
Name some formulations of drugs
Tablets Capsules Linctus Emulsions Elixirs (alcohol base) Syrups Sprays
How does lipid solubility of a drug affect its movement through membranes?
Drugs need to be largely lipid soluble for absorption across the plasma membranes in the small intestine to occur.
If they are water soluble they will be removed by the kidneys and will have little or no therapeutic effect
Which tissue has the highest blood flow?
The kidney
