1. Drug Dose calculation.pdf for veterinary

dose calculation for drugs for veterinary

1. DCllii DCllii D
ose 
C
a
lcu
lat
ions 
in 
D
ose 
C
a
lcu
lat
ions 
in 
VeterinaryPharmacology VeterinaryPharmacology Veterinary
 Pharmacology Veterinary Pharmacology

2. DrugDose Drug
 Dose
•Thedoseofadrugistheamountofdrugadministeredatone
h
h
dd
ff
(
b
l
bl
timetoac
h
ievet
h
e
d
esire
d
e
ff
ect
(
can
b
einm
l,mg,g,ta
bl
ets,
etc.)
•Loading dose:initial dose o
f
drug given to get the drug
concentration up to the therapeutic range in a very short
periodoftime
•Maintenance dose:dose of drug that maintains or keeps the
druginthetherapeuticrange
•Totaldailydose:totalamountofdrugdeliveredin24hours

3. DrugDosage Drug
 Dosage
•Thedosageof a drug isthe amount of drug per
il
’
bd
ih
an
ima
ls
’
b
o
d
ywe
ig
h
tormeasure
–Examplesincludemg/kgorg/lb
•Dosageinterval:howfrequentlythedosageisgiven
–ExamplesincludeBIDorTID
•Dosage regimen:dosage interval and the dosage
together
Examples
include
Examples
include
–30mg/kgTID,
–5g/lbBID

4. DoseCalculations Dose
 Calculations
•
Mustknow
correctamountofdrug
toadministertoa
Must
 know
 correct
 amount
 of
 drug
to
 administer
 to
 a
 
patient
•Must be in same s
y
stem of measurement
y
•NB:
–
dru
g
s can be measured in u
g
,
 m
g,
 g,
 g
r
,
 ml
,
 l
,
 units
g
g
,g,g,
g
,,,
–drugs can be dispensed or administered in tablets, ml, l, 
capsules

5. DoseCalculations Dose
 Calculations
Metrology:  ¾
isthestudyofweightsandmeasuresasappliedto
¾
is
 the
 study
 of
 weights
 and
 measures
 as
 applied
 to
 
the preparation of drugs.
‰Two S
y
stem
y
¾The metric system: kg, g, mg, ug; l, ml, ul
¾The apothecary system: ounce, drums, grains, minims ‰The metric system preferred to The apothecary system
¾1kg= 1000g
¾1g= 1000mg
¾
1mg 100ug
¾
1l=1000ml
¾
1mg
=
100ug
¾1ug=1000ng
¾
1l=1000ml

6. Severalconversionequivalents Several
 conversion
 equivalents
¾
1kg=
22pounds
¾
1kg=
 
2
.
2
 pounds
¾1g= 15 grains ¾
l
ii
¾
1m
l= 15 m
in
ims
¾20 drop= 1ml
¾1 tea spoonful= 5ml ¾
1coffeecup
=
60ml
¾
1
 coffee
 cup
60ml

7. Solutions Solutions
•Solutionsare a homogeneous mixture of two or
moresubstancesinwhichthemoleculesoratomsof
thesubstancesarecompletelydispersed.
–Thedissolvingsubstanceofasolutionisreferredtoasthe
solven
t
(liquid)
–Thedissolved substanceof a solutionisreferredto asthe
solute
(solid
or
particles)
solute
(solid
or
particles)
–Substancesthatformsolutionsarecalledmiscible –
Substances that do not form solutions are called immiscible

8. WorkingwithSolutions Working
 with
 Solutions
•The amount of solute dissolved in solvent is known as the 
concentration
•
Concentrationsmaybeexpressedas Concentrations
 may
 be
 expressed
 as
 
–parts (per some amount), 
–weight per volume, 
volumepervolumeand
–
volume
 per
 volume
, 
and
 
–weight per weight
•Usually reported out as percents or percent solution
•
NB:apercentisthepartsperthetotaltimes100 NB:
 a
 percent
 is
 the
 parts
 per
 the
 total
 times
 100

9. Rules of Thumb When Working with 
li
So
lut
ions
•Parts: 
–
parts per million(PPM)  means 1 mg of solute in a kg (or l) 
of solvent (1:1000)
–1ppm=1mg/kg or 1mg/l
dld
•Liqui
d
 in 
liqui
d
: 
–the percent concentration is the volume per 100 volumes 
of the total mixture (1 ml/100 ml)
S lidilid
•
S
o
lid
s 
in so
lid
s: 
–the percent concentration is the weight per 100 weights of 
total mixture  (60 mg/100 mg)
S lidili id
•
S
o
lid
s 
in 
li
qu
id
: 
–the percent concentration is the weight in grams per 100 
volume parts in milliliters (dextrose 5% = 5 g/100ml)

10. PercentConcentrationCalculations Percent
 Concentration
 Calculations
•Pure drugsare substances that are 100% pure •Stock solutionis a relatively concentrated solution from which 
more dilute solutions are made
•
Ratio
proportionmethod:
•
Ratio
‐
proportion
 method:
 
–one method of determining the amount of pure drug needed to make 
a solution
–
Amountofdrug/amountoffinishedsolution=%offinished
–
Amount
 of
 drug/amount
 of
 finished
 solution
 =
 %
 of
 finished
 
solution/100% (based on a pure drug)
•Remember that the amount of drug used to prepare a 
solutionisaddedtothetotalvolumeofthesolvent solution
 is
 added
 to
 the
 total
 volume
 of
 the
 solvent

11. AnotherWaytoDetermineVolume Another
 Way
 to
 Determine
 Volume
Volumeconcentrationmethod/dilution: Volume
 concentration
 method/dilution:
•V
s 
= volume of the beginning or stock solution
•
C
=concentrationofthebeginningorstocksolution
C
s 
=
 concentration
 of
 the
 beginning
 or
 stock
 solution
 
•V
d
= volume of the final solution
•
C
=concentrationofthefinalsolution
•
C
d 
=
 concentration
 of
 the
 final
 solution
V
s
xC
s
=
V
d
x
C
d
V
s
 x
 C
s
 
 V
d
x
 C
d

12. DrugConcentrationsinPercents Drug
 Concentrations
 in
 Percents
•Dru
g
 concentrations are sometimes listed in 
p
ercents
gp
•Parts per total = parts (in g) per 100
•The front of the vial s
p
ecifies the concentration 
p
–(for example, 2% lidocaine=2g/100ml)
•Use X 
g/
100 ml to determine dose
g/

13. Exercises Exercises
1Therecommendeddosagetobeadministered 1
. 
The
 recommended
 dosage
 to
 be
 administered
 
to sheep is 10mg/kg of BW and the solution is 
labelled10%Howmanymlofthedrugshould labelled
 10%
. 
How
 many
 ml
 of
 the
 drug
 should
 
be admif the BW of the sheep is 60kg. 
Ans. 6ml
10mg=1kg
10%=10g/100ml=
¾
10,000mg
=
100ml
Xmg=60kg
ans=600mg
¾
10,000mg 100ml 600mg=   xml
Ans
=
6ml
Ans
 6ml

14. 2.
The general dose of atropine is 0.05mg/kg of BW
and the solution is labelled 0.1%. How many ml of
the drug should be adm if the wt of the animal is
50
kg
50
kg
.
Ans: 2.5ml
0.05g=1kg
0.1g=100ml where 0.1%=0.1g/100ml
2.5m
g
=x 
X= 50kg
¾2.5mg
g
Ans AnsX=2.5ml X=2.5ml

15. Exerciseproblems(assignment) Exercise
 problems
 (assignment)
1. A solution o
f
sodium h
yp
ochlorite contains 5% o
f
activated
yp
chlorine.Ifwewanttoprepareasol.of1:10,000howmany
mlH2Oweneedtoaddtoobtainthisconc.?
2. The injectable B‐complex contains 1% of thiamine, 0.1% of
riboflavine
,
17.6%Ca
p
antotenate.Whatistheconc.o
f
each
,
p
vitamininmg/ml?
3. I
f
wewanttoadminister1.5mlo
f
Naphenobarbitoneinthe
dose of 15mg/kgBWtothe rabbitthatweighs5kg.Inwhat
conc
you
may
dissolve
the
drug?
conc
you
may
dissolve
the
drug?