Transcript Calculation of parenteral dosages of medication

Calculation of parenteral
dosages of medication
Parenteral doses must be in liquid
form for injection
Parenteral available as:
Liquids in prefilled disposable cartridges or
disposable syringes with specific amt of drug
in specific volume.
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Meperidine 50 mg/ml or 100 mg
Single/ multi dose ampules or vials containing
specific amt of liquid form of drug in specific
volume

Epinephrine [Adrenalin] 1:1000 in 0.1 ml
Ampules or vials containing powder or
crystals which must be reconstituted
Disposable syringes or cartridges
Calculate dose
May need to discard remainder to
prepare dose
E.g. diazepam 5 mg IM

Available 2 ml disposable syringe labeled 5
mg/ml
Parenteral drugs in single or
multi-dose ampules and vials
Calculate dose if different from label
Determine amt to be administered
Withdraw desired amt from ampule or
vial
E.g. chlorpromazine 12.5 mg IM

Available chlorpromazine 25 mg/ml in 1 ml
ampule
Note
Amt in any multidose vial is not entered
into the equation
Enter as the quantity Q the amt
available contained in a specific volume
When dose is less than 1 ml, may need
to convert to answer to minims using
15 or 16 minims/ml.
example
Chlorpromazine 10 mg IM
Available 25 mg/ml
Answer is 2/5 X 15 minims = 6 minims
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(also 0.4 cc)
WARNING
Always check drug labels carefully.
Some may be labeled differently from
others of same medication.
Narcan
Epinephrine
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2 ml amp labeled 0.25 mg/2 ml
2 ml amp labeled
5 mg/1 ml
Parenteral drugs in dry form
Available in dry or crystal form and must
reconstitute or make into liquid form to be
removed and administered.
Usual directions:

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Name of solution to be used (sterile water
or normal saline for injection)
Amt of diluent
ALWAYS check label carefully for
instructions!
Methicillin sodium:
Reconstitute 1 g vial add 1.5 ml of
sterile water for injection of sodium
chloride for injection. Each
reconstituted ml contains approx 500
mg of methicillin.
Amt for IM, ID or SC involve very sm
amts
Amt of IV may involve 50 ml or more
Add to label when reconstituted
Amt of diluent added
Concentration of dose of drug in ml e.g
500 mg/ml
Date of reconstitution
Exp date.
Handling solutions:
Chemicals may be fragile:

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Affected by heat, light and time
Change or deteriorate
Reason why manufactured as powder
Reconstitute and use within few hrs and
protect from light
Antibiotics
steroids
example
cephalothin (Keflin) 500 mg q6h IM
Available multi-dose vial containing 3 g
of powder.
Prepare to 500 mg = 1 ml
Convert g to mg
Set up ratio:proportion or D/A
Give cephalosporin 200 mg/1 ml
Available: 1 g vial powder
Amt of diluent to add?
Add enough diluent so sode ordered
may be given in no more than 0.5 to 1
ml
problems
See handouts
Insulin
Parenteral medication replacing insulin not
produced by pt.
Calculating and preparing insulin dosage
unique:
1. Standardized measure: unit
 Available in 10 ml vials in two strengths
(concentrations):
 U-100 = 100 units per 1 ml solution
 U-500 = 500 units per 1 ml solution (rarely used)
Insulin
2. Should be drawn up in special insulin
syringe calibrated in units.

If insulin syringe not available may use TB
syringe calibrated in minims
3. Insulin order, insulin bottle, insulin
drawn up should ALWAYS be rechecked
by another nurse for accuracy.
Insulin
When two different types of insulin
ordered, give both at same time in
same syringe.
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Short-acting (regular)
Intermediate or longer-acting (NPH or zinc)
Dray up regular insulin first, then longer
acting type.
Give both in same syringe
Insulin example
Order: 20 units regular (Iletin) insulin
U-100 and 30 u NPH U-100 before
breakfast.
Prepare: use a U-100 syringe for total
of 50 units.
Draw up 20 units regular insulin
Draw up 30 units NPH insulin to equal
50 U in syringe.
To use a TB syringe for insulin
Calculate number of minims:
Insulin desired
insulin available X 16 minims=
number of minims to administer
E.g. 80 U regular U-100 insulin
calculation
D= 80 U
A = 100 U
64
X 16 = 5
= 12.8 minims
NOTE: You MUST use 16 – not 15minims/ml for very accurate
calculations.
Intravenous infusions
Drug ordered to add to an intravenous
IV fluid
Amt of fluid to be adm over a specific
period of time:
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E.g. 125 ml / h
Determine IV flow rate: drop factor
Drop factor
Drop factor ( number of drops/ml)
given on pkg containing drip chamber
and IV tubing
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Use one of three methods for determining
IV infusion rate: