IV Drug Administration

Question 1

Reasons for IV administration

Answer 1

• Medicine is not available in another form
• Cannot tolerate medication by another route
• Constant or high blood level of medicine is needed
• A rapid onset of effect is needed
• Some medications are more effective via IV
• Rarely, to ensure compliance

Question 2

Disadvantages of IV administration

Answer 2

• Increased cost and time to administer the medicine
• Requires trained staff to administer (plus location)
• Rapid onset of action
  Volume of fluid needed to dilute the medicine
• Can cause discomfort/pain to the patient
• Health risks (e.g. infection)

Question 3

Types of intravascular devices (IVDs)

Answer 3

Peripheral venous catheters

Central venous catheters:
– Peripherally inserted CVCs
– Skin-tunneled CVCs (e.g. Hickman and Broviac lines)

Arterial catheters

Question 4

Continuous infusion

Answer 4

– Stable drugs
– Short half-life
– Time dependent effects
– Needs dedicated IV site

Question 5

Bolus injection

Answer 5

– Rapid response required
– Incompatibilities
– Unstable drugs

Question 6

Intermittent infusion

Answer 6

– Unstable drugs
– Long half-life
– Concentration dependent effects
– Less compatibility concerns

Question 7

Complications of IV drug administration

Answer 7

• Fear / Phobia / Pain
• Infection / Sepsis
• Thrombophlebitis
• Extravasation / Infiltration
• Emboli
• Anaphylaxis / Hypersensitivity - Overdose

Question 8

Red man syndrome

Answer 8

Hypersensitivity reaction due to histamine release
– erythematous rash of face, neck, and upper torso
– diffuse burning, itching, generalised discomfort
– rare cases: hypotension, angioedema, chest pain, dyspnea

Question 9

Vancomycin

Answer 9

– Treatment of MRSA

Question 10

incidence of red man syndrome is reduced by

Answer 10

– Slowing infusion rate

– More dilute drug solution

Question 11

Complications of IV drug administration - the actual solution

Answer 11

Insufficient mixing

Stability of medicines in solution
– Light (e.g. total parenteral nutrition [TPN]) – Temperature (e.g. insulin, TPN)
– Concentration (e.g. amiodarone)
– pH (e.g. midazolam)

Interaction of medicines with the syringe/bag

Question 12

Bioavailability

Answer 12

Fraction of unchanged drug that reaches the systemic circulation.
IV injection gives 100% bioavailability.

Question 13

Plasma drug concentrations

Answer 13

IF drug is infused at a constant rate AND no drug is removed from the body, then the graph of plasma concentration against time would be a straight line

Question 14

For most drugs, the amount of drug eliminated per unit time is related to

Answer 14

the concentration of drug in the plasma (first-order kinetics):
– Higher concentrations, more drug is removed per unit of time.
– Lower concentrations, less drug is removed per unit of time.

Question 15

Plasma drug concentration during IV infusion

Answer 15

Plasma concentration increases during infusion until rate of input equals rate of output
• “Steady state”

Question 16

Clearance

Answer 16

defined as the volume of blood or plasma cleared of drug in a unit time – e.g. 10ml/min

In first order kinetics, whilst amount of drug eliminated per unit time varies, CL is a constant

Question 17

clearance =

Answer 17

10ml/min

Question 18

Plasma steady state conc. (Css)

Answer 18

the rate of the drug administered (Ko)
divided by
volume of plasma Cleared of drug per unit time (CL)

Question 19

The time taken to reach Css depends on:

Answer 19

elimination half-life (t1/2)

Question 20

t1/2 directly depends on

Answer 20

the volume of distribution (Vd) and
inversely on the clearance (CL) of drug from the body:
In2xVd
divided by 
CL

Question 21

Clinical impact

Answer 21

What happens if your patient’s CL is lower or
higher than expected?
– To the steady state plasma concentration?
– To the time taken to reach that steady state?
What happens if you increase or decrease the dose of a drug?
– To the steady state plasma concentration?
– To the time taken to reach that steady state?