Transcript PowerPoint-Präsentation - NHS Greater Glasgow and Clyde

PHARMACEUTICAL ASPECTS
OF
INTRAVENOUS DRUG ADMINISTRATION
Glasgow Royal Infirmary
Pharmacy Department
Differences IV  ORAL route
IV administration leads to:
 Higher peak concentrations
 Greater total quantity of drug
absorbed
Conc.
 Avoids 1st pass metabolism
 However requires more
training, knowledge, skills
and precautions
time
IV route - Advantages
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Emergency situations / immediate response
e.g. adrenaline in cardiac arrest.
Loading dose e.g.digoxin, phenytoin
Patient unable to swallow or tolerate other
routes
Sustained drug levels required
Drug cannot be given by another route
because of its chemical property e.g.
cytotoxics, cefotaxime
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Less painful than I.M. injection.
Administration can be stopped quickly
Allows dosing of unconscious,
uncooperative and uncontrollable
patients.
To achieve effects unattainable by oral
administration.
IV route - Disadvantages
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 Risk of toxicity
Risk of embolism
Risk of extravasation/phlebitis
Fluid overload
Problems with compatibility + stability
Risk of microbial contamination
Increased cost
More training required
BOLUS 3-10 minutes
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Quick/easy/economical
Tendency to administer too quickly
causing damage to veins.
Sudden anaphylactic reactions
Only limited volumes can be
administered
Intermittent IV INFUSION
20-120 minutes
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One-off or repeated doses
E.g. Gentamicin, vancomycin,
erythromycin
High plasma concentration achieved
rapidly over longer periods.
Continuous IV INFUSION
Delivers constant level of drug
 Used for drugs with a rapid elimination rate
or a very short half-life e.g. midazolam
BUT
 Fluid overload, incompatibility, contamination,
incomplete mixing, phlebitis and rate
calculations can be problematic.
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Formulation of I.V. drugs
Reconstitution required
-Dry powder e.g. amoxicillin
-Allows prolonged storage
BUT
- Is time consuming
- Risk of contamination, foaming, glass
particles, pressurised vials.
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Solutions needing further dilution
e.g. Ranitidine, Amiodarone
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No reconstitution necessary
BUT
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Time consuming
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Prone to vacuum/pressure problems
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Can cause glass breakage
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Risk of microbial contamination.
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‘Ready to use’
No further dilution needed
 Come in bags/small volume amps/syringes e.g.
metoclopramide, adenosine, morphine PCAs
 Easy to use & time saving
 Minimal microbial contamination
BUT
 Microbial contamination
 Fluid overload
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Factors influencing Stability &
compatibility
A proportion of the drug will be lost
between time of preparation and
entry into the bloodstream by
degradation, precipitation or an
interaction.
Degradation
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By hydrolysis in aqueous solution
May be accelerated by pH change
Minimised by using reccomended
diluent
Photodegradation
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Breakdown by light. e.g. Vitamin A,
sodium nitroprusside, liposomal
amphotericin.
May not be clinically important provided
direct exposure to strong daylight is
avoided e.g. furosemide.
Precipitation
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Precipitates are inactive but harmful:
can block catheters, damage capillaries
and cause emboli.
May be transparent or pale
Affected by differences in pH
Anions and cations mix to form ion pairs
Most drugs are more soluble as temp.
increases
Blinding of drugs to plastics
Most equipment made from plastic
 Drug binding difficult to predict as
it depends on:
Conc. Flow rate, vehicle, surface
area, temp. pH and time.
 Care with insulin, diazepam,
nitrates....
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Leaching of plasticisers
Oils and surfactants contained in PVC
bags can leak out and affect
compatibility and stability of drugs.
e.g. Ciclosporin infusion must be used
within 6 hours as polyethoxylated castor
oil in the solution causes phthalate to
leach from PVC.
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Summary
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Add one drug at a time following manufacturers
advice
Mix thoroughly to avoid layering
Examine solution regularly
Add most concentrated or most soluble additive
first
Strongly coloured solutions will hide reactions
Observe patient for ADR’s
Intravenous Antibiotics
State for each of the following:
Diluent & volume required for reconstitution
Volume required for dose
Type of injection
Gentamicin 260mg Erythromycin 750mg
Co-amoxiclav 1.2g Metronidazole 500mg
Tazocin 4.5g
Example (1)
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How would you prepare and administer
Flucloxacillin 1g IV?
Each 1g vial should be reconstituted with
20ml WFI (SPC)
Add 20ml reconstituted solution to 100ml NaCl
0.9% or glucose 5% (BNF)
Can be given as an infusion over 30-60min. or
bolus injection over 3-4 min. (BNF & SPC)
Example (2)
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How would you prepare & administer Vancomycin
1250mg
Each 500mg vial should be reconstituted with 10ml WFI
– Use 3 vials (BNF Appendix 6)
Got 1500mg  30ml
1250mg  1250 x 30 / 1500 = 25ml
Conc. of infusion fluid must be ≤ 5mg/ml (BNF)
Therefore put 25ml into 250ml of Nacl 0.9% or Glucose
5%
Must be given as an infusion (SPC & BNF)
References to use
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BNF appendix 6
BNF monographs
SPC (www.emc.medicines.org.uk)
Technical leaflet
JHO handbook
Medusa I.V. drugs guidance manual
(www.medusa.wales.nhs.uk)
Ward clinical pharmacist
Medicines information (ext 24407)
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How would you prepare and administer:
Gentamicin 260mg
Co-amoxiclav 1.2g
Tazocin 4.5g
Erythromycin 750mg
Metronidazole 500mg
Answers
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Gentamicin 260mg
4 x 80mg/2ml vials. Withdraw 6.5ml
and add to 100ml NaCl 0.9% or Glucose
5%. Give over 30-60 min.
Co-amoxiclav 1.2g
1.2g vial reconstituted with 20ml WFI.
Bolus (3-4min.) or infusion in 50-100ml
NaCl0.9% given over 30-40min.
Answers (cont)
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Tazocin
4.5g vial reconstituted with 20ml WFI or
NaCl 0.9%. Bolus (3-5min.) or infusion in
100ml NaCl 0.9% over 20-30min.
Erythromycin 750mg
1000mg vial reconstituted with 20ml WFI.
Withdraw 15ml (750mg) and add to 250ml
NaCl 0.9%. (Cannot get 150ml bag!!)
Infuse over 60min.
Answers (cont.)
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Metronidazole 500mg
100ml bag 5mg/ml = 500mg. Infuse
over 20 min.