Dosing and Calculations

Question 1

Ratio

Answer 1

the relative magnitude of two like quantities (Ie: 20g:4g terms must be in the same units)

Question 2

Proportion

Answer 2

An expression of the equality of two ratios
A/B=C/D
Ex: If 3 tablets contain 975 milligrams of aspirin, how many milligrams should be obtained in the 12 tablets? 3900

Question 3

Inverse Proportion

Answer 3

If 10 pints of a 5% solution are diluted to 40 pints what is the percentage strength?
(10)(0.5)=(40)(x) is 1.25%

Question 4

Dimensional analysis

Answer 4

Canceling out units
A medication order calls for 1L dextrose 10% infusion to be administered over an 8hr period. Using an IV pump set that delivers 10drops/milliliter how many drops a minute should be delivered to the patient?
1000ml/8hr X 10 drops/mL X 1hr/60 minutes = 21 drops/min

Question 5

Metric system

Answer 5

1000mcg=1mg
1000mg=1g
1000g=1kg
1inch=2.54cm
1tsp=5mL
2.2lb=1kg

Question 6

Median effective dose

Answer 6

Amount that produces desired intensity of effect in 50% of individuals tested

Question 7

Median toxic dose

Answer 7

amount that produces toxic effects in 50% of individuals tested

Question 8

Minimun effective concentration

Answer 8

Minimum dose we see working in the blood

Question 9

Minimum toxic concentration

Answer 9

minimum toxic level in the blood

Question 10

Pediatrics

Answer 10

Neonate- birth to 1 month
Infant- 1 month to 1 year
Early childhood- 1 year to 5 years
Late childhood- 5 years to 12 years
Adolescence- 13 years to 17 years

Question 11

Pediatric Rx restrictions

Answer 11

Consider age and weight
Based on weight often expressed as mg/kg
Based on body surface area

Question 12

Expressions of Concentrations

Answer 12

%w/v=grams/100mL
%v/v=mL/100mL
%w/w=grams/100grams

Question 13

IBW

Answer 13

Males- IBW= 50kg + 2.3kg for each inch over 5 ft

Females- IBW= 45.5kg + 2.3kg for each inch over 5ft

Question 14

Adjusted Body Weight

Answer 14

AjBW=IBW + 0.4(ABW-IBW)

Question 15

Creatinine Clearance

Answer 15

Tests the functioning of the kidneys
CrCl= (140-age) x IBW / (Scr x72) 
(x0.85 for females)
*if actual weight 30% obesity use adjusted
*Raise Scr to 1 if pt> 65y/o
Normal creatinine is less than 1