IV drug administration Flashcards
what are the reasons for IV administration?
- medicine is not available in another form
- cannot tolerate medication by another route (unconscious)
- constant high blood level of medicine is needed
- a rapid onset of effect os needed
- some medications are more effective via IV
- rarely, to ensure compliance (make sure they acc take it)
what are the different types of intravascular devices (IVD’s)?
- peripheral venous catheters
- central venous catheters
- arterial catheters
describe central venous catheters?
- they are peripherally inserted
- the skin is tunnelled in (allows long term access to that route)
- doctors will place it in a large vein to give meds or take blood quickly
- if the med is delivered to a large volume of blood in larger veins, this can decrease the conc of the medicine making it safer.
what are the 2 types of CVC?
1- peripherally inserted CVC (PICC)
- tube inserted into the arm and guided up to the SVC
2- skin tunnelled CVC
- multiple accès points for meds
what are the disadvantages of IV drug administration?
- increased cost and time to administer the meds
- requires trained staff
- rapid onset of action
- volume of fluid needed to dilute (can’t just give them 3L of something)
- discomfort/pain
- health risk (infection)
what are the 3 different methods of administrating IV medication?
- continuous infusion
- intermittent infusion
- bolus infusion
when would you use continuous infusion?
- used if the drug is stable
- drug has a short half life
- there are time dependant effects
- it must have a dedicated IV site (need to be able to control it)
when would you use intermittent infusion ?
- if the drug is unstable
- the drug has a long half life
- it has concentration dependant effects
- less compatibility concerns
when would you use bolus injection ?
- a rapid response is required
- useful for drug incompatibilities as we can administer the drug to a place that it won’t interact with another drug.
- useful for unstable drugs
- one of drug
what are the hazards and complication OF iv therapy?
- fear / phobia (physiological factors)
- infection/sepsis
- thrombophlebitis (this is a swollen or inflamed vein due to a blood clot- can be hard to see due to skin colour)
- extravasation and filtration
- emboli
- anaphylaxis
- overdose
what is extravasation and infiltration?
- when a vessican has went into a place that it shouldn’t be
- what you are delivering has went into the tissue and not into the blood stream.
what is red man syndrome?
a hypersensitivity reaction due to histamine release
what drug causes red man syndrome?
vancomycin (treatment for MRSA)
signs of red man syndrome?
- erythematous rash of face, neck and upper torso
- burning, itching, generalised discomfort
- in rare cases: hypotension, angioedema, chest pain, dysponae
how do you reduce incidence of red man syndrome?
- slowing diffusion rate
- more dilute drug solutions
VANCOMYCIN
what is the:
1- loading dose
2- volume of sodium chloride 0.9% or 5% glucose
3- duration of infusion
for body weight of:
< 40kg
40-59kg
60-90kg
>90 kg
< 40kg:
1- 750mg
2- 250 ml
3- 1.5 hrs
40-59kg:
1- 1000mg
2- 250ml
3- 2 hrs
60-90kg:
1- 1500mg
2- 500ml
3- 3 hrs
> 90 kg:
1- 2000 mg
2- 500ml
3- 4 hrs
what are complications of IV drug administration?
- insufficient mixing (could change drug conc)
- stability of the med in solution
- interaction of the drug with syringe/bag
different examples of things that effect the stability of the drug?
- light
- temp
- conc
- pH
bioavailability?
the fraction of unchanged drug that reaches the systemic circulation
bioavailability of IV drugs?
100% bioavailability
does the average plasma conc stay the same or change depending on the infusion rate?
the average plasma conc will stay the same no matter the infusion rate.
if the drug is infused at a constant rate and no drug is removed, what would a graph of plasma conc look like and what are the relationships?
the graph of plasma concentration against time would be a straight line and the relationship would be directly proportional.
why does this linear relationship of plasma conc and time not usually happen?
because most drugs follow first order of kinetics and essentially as soon as the drug reaches the plasma it is going to start to be removed depending on the affinity the drug has for the plasma.
what does an increase or a decrease in conc of drug in the plasma do to the time it takes to remove it?
increased (higher) drug conc in plasma = removed at a quicker rate (more drug removed per unit time)
decreased (lower) conc of drug in plasma= it will be removed more slowly. ( less drug is removed per unit time)
for most drugs, what is the amount of drug eliminated per unit of time related to?
it is related to the concentration of the drug in plasma.
describe first order of kinetics?
occur when a constant proportion of the drug is eliminated per unit time
using first order of kinetics, what would a graph look like of plasma conc against time?
the graph will bend towards a plateu when the rte of drug in equals the rate of drug out.
until when, will the plasma conc increase during infusion?
until the rate of input = output
“steady state”
what is the clearance of a drug?
this is defined as the volume of blood or plasma cleared in a unit of time
(related to the rate at which the drug is removed, divided by the concentration of that drug in the plasma)
in first order kinetics what is the clearance of a drug?
whilst the amount of drug eliminated per unit time varies, the clearance will remain constant.
plasma conc steady state value equation?
the rate of the drug administered (K0)
/
volume of plasma cleared of drug per unit of time (CL)
what does the time taken to reach the Css depend on?
elimination half life (t1/2)
what does t1/2 depend on?
directly depends on the volume of distrubution (Vd) and inversely on the clearance (CL) of the drug in the body.
calculation for t1/2?
t1/2= In x Vd
/
CL
what does volume of distrubution (Vd) depend on?
how big the thing actually is, could be a small human or a big one.
what contributes to clearance?
kidneys
liver
What is the visual infusion phlebitis score?
Visual infusion phlebitis score
what is vancomycin given for?
deep seated infection
- we give a larger initial dose (loading dose)
- then we give a diluted dose over a long period of time to reduce the risk of red man syndrome
- this will maintain blood plasma levels
what is the loading dose?
the initial higher dose of a drug that may be given at the beginning of a course of treatment before dropping it down to a maintenance dose.
- most useful for drugs that are eliminated slowly from the body.
