Drugs Handling In The Body Flashcards
Name 2 positive aspects of oral administration?
Convenient for patient
Absorption for small intestine- large surface area
Identify the negatives of oral administration
Not appropriate for all drugs
Absorption is variable eg how lipid soluble is the drug
Absorption depends on stomach content (may be destroyed)
Rate of gastric emptying
Degradation in stomach
Define bioavailability
Is the amount of dose which reaches circulation as intact drug
Name the positives of topical administration and define it?
Skin creams and convenient and poorly absorbed which reduces the risk of overdosing
Name the negatives of tropical administration
Negative effects on skin eg hydrocortisone causes thinning of the skin
Define transdermal administration and explain the benefits
Long acting
Useful when you want low levels over a long period of time
Suitable for wide patient groups
Name the negatives of transdermal administration
Variable absorption
Drug must be lipid soluble
Drug must be potent
Name 2 positives and 1 negative of rectal administration
+ local or systemic effect
Useful if vomiting or can’t swallow
- trained to administer
Name 2 positives and 1 negative of inhalation administration
+rapid change in conc of drug due to LSA of lungs
Local or systemic effect
-difficult to ensure drugs reach site of action
Name 6 parenteral routes
Intravenous, intramuscular, intradermal, subcutaneous, intrathecal, epidural
Name the positives of the parenteral routes
Rapid action
Bypass stomach and liver
Lower dose required
Patient controlled syringe drivers
Describe the negatives associated with parenteral routes
Required trained person
Extreme care required
Accidental overdose
Painful
What are excipients ?
These are additional components added to the drug to turn into a medicine, may improve taste or stabilise drug
A medicine = a active drug + _________
Excipients
Excipients can impact upon
Bioavailability and duration of therapeutic effect
Describe the chain of events which occur in the absorption of oral tablets
Tablet > granules > fine particals > solutions
Define dissolution rate
How fast it becomes a solution
For a drug to cross a cell membrane they must be lipid soluble or water soluble ?
Lipid soluble
Name 4 method of drugs crossing a cell membrane
Passage trough water channels
Endocytosis
Passive diffusion
Facilitated or active transport
Distribution is the
Transfer of absorbed drug into and out of various tissues in the body from the blood stream
What effects the extent of distribution
Lipid solubility of drug
Blood flow to tissues
Binding of drugs to proteins
Free drugs can bind to ______ in the plasma, and only ______ unbound drugs can diffuse across membranes and have an effect
Proteins
Free
Elimination =
Metabolism + excretion
Most drugs are lipophilic what does this mean ?
They re-circulate ( as they are just reabsorbed back into blood stream when they reach liver)
In order to stop recirculating drugs must be converted to what ????
Water soluble
Lipid soluble > water soluble > excretion
Drugs metabolism is the _____ conversion of _______ soluble into a more _______ soluble one
Enzyme mediated
Lipid
Water
Metabolism mainly takes place in the …
Liver, kidney, lungs, GI tract, brain and plasma
Name the phases of metabolism
Phase 1 and phase 2
Explain what happens in phase 1
Modifies chemical structure of drug to make it slightly more water soluble and prep for phase 2
Explain pharmacological activation and identity which phase it occurs in
Is when drugs have to be metabolised to be activated and in phase one as products can be more reactive that parent drug
Explain what happens in phase 2
Conjugate drug to large molecules eg amino acids + sulphate groups
The products of phase 2 are generally
Water soluble and easily excreted Increase molecular weight Inactive (pharmacological inactivation) > decreased receptor affinity Enhanced excretion
With drug interactions, Drugs metabolising enzymes can either be what ?
Induced eg alcohol induced liver enzymes
Inhibit eg fluoxetine( Prozac) + grapefruit juice
Excretion is the
Removal of drugs from the body
Excretion takes places via
Urine, bile, faeces, lungs and skin
To increase drug excretion;
Increase blood flow to kidneys
Decrease plasma protein binding
Half life is ….
The time is takes for the amount of drug in the body to decrease to one half of the peak level- this is the rate at which drugs are eliminated from the body
Most of drug (97%) is eliminated after how many half life’s?
5 regardless of dose of route
What does the half life tell us ?
The time we should leave between stoping one drug and starting the next to avoid interactions
Estimates how long it takes for toxic concentration to occur
What is at the top and bottom of the therapeutic window ?
Top is min toxic concentration
Bottom in min therapeutic concentration
Name the 6 routes of transmission
Oral, topical, transdermal, rectal, inhalation, parental
