Dosing and Calculations Flashcards
(15 cards)
Ratio
the relative magnitude of two like quantities (Ie: 20g:4g terms must be in the same units)
Proportion
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
Inverse Proportion
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%
Dimensional analysis
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
Metric system
1000mcg=1mg 1000mg=1g 1000g=1kg 1inch=2.54cm 1tsp=5mL 2.2lb=1kg
Median effective dose
Amount that produces desired intensity of effect in 50% of individuals tested
Median toxic dose
amount that produces toxic effects in 50% of individuals tested
Minimun effective concentration
Minimum dose we see working in the blood
Minimum toxic concentration
minimum toxic level in the blood
Pediatrics
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
Pediatric Rx restrictions
Consider age and weight
Based on weight often expressed as mg/kg
Based on body surface area
Expressions of Concentrations
%w/v=grams/100mL
%v/v=mL/100mL
%w/w=grams/100grams
IBW
Males- IBW= 50kg + 2.3kg for each inch over 5 ft
Females- IBW= 45.5kg + 2.3kg for each inch over 5ft
Adjusted Body Weight
AjBW=IBW + 0.4(ABW-IBW)
Creatinine Clearance
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
