Dosages

How long are prescriptions for controlled medications in the DEA schedules 3, 4, and 5 valid?

6 months Teaching Points Prescriptions for controlled substances in schedules 3, 4 and 5 are valid for 6 months unless specified by the doctor.

If a child is 60 months old and the adult dose is 500 mg, how much medication should the child receive using Young's rule?

167mg Teaching Points 60 months/12 months/year = 5 years. [(5)/(3+12)] x 500 mg = 167 mg.

2000 mL of solution is given intravenously at 100 mL/hr using an administration set with a drop factor of 20 gtts/mL. If the infusion starts at 0700, when will it end?

300 Teaching Points Calculate time = volume/time or 2,000 mL/100 mL/hr = 20 hour. The bag was hung at 0700 hours and it will last 20 hours. 0700 hour + 2000 hours = 0300 hour on the next day.

A patient is prescribed normal saline at a total volume of 1800 mL over 24 hours. What is the volume per hour?

75mL

A medication is ordered 0.75 mg IV stat. The stock vial reads 2.5 mg per 2 ml. How many milliliters will you need for this administration?

0.6mL

There is a vial of haloperidol labeled as 20 mg/2ml. In order to administer 7.5 mg, how much should be withdrawn in a syringe?

0.75mL Teaching Points If there is 20 mg in 2 ml, then this means the vial contains 10 mg in 1 mL. For a dose of 7.5 mg, one needs to inject 0.75 mlL

One liter of total parenteral nutrition (TPN) is administered at 80 mL/hr, using an administration set with a drop rate of 15 gtts/mL. If the TPN is started at 13:00, when will it be finished?

01:30 the next day Teaching Points The gtts conversion rate is superfluous data. Convert 1 liter to mL; 1L X 1,000 mL/L = 1,000 mL. Determine the number of hours the IV will run by dividing the volume by the drip rate. Calculate: time = 1,000 mL/80 mL/hr = 12.5 hours. Starting the IV at 13:00 will result in it finishing at 01:30 the following morning; (13:00 +12.5 = 25.5, then subtract 12 hours to convert to time the next day).

Pediatric patients require close monitoring of fluid status. Daily fluid maintenance defined as the amount of fluid a child needs in a twenty-four-hour period, including oral and parenteral fluids, plays a vital role in the fluid status of a child. A daily fluid maintenance formula aids us in calculations with pediatric patients. How much fluid is a daily requirement based on this method for a 35-kg child in milliliters?

1,800mL Teaching Points The first 10 kg of body weight 100 mL/kg is given. For the next 10 kg of body weight, 50 mL/kg is added to the baseline. Each kg beyond 20 kg of body weight is another 20 mL/kg. 35 kg = 10 kg + 10 kg + 15 kg, so the first part of the formula addresses the fluid amount for the first ten kilograms of this thirty-five-kilogram child. First, 10 kg is 100 mL/kg, so 10 x 100 = 1,000 mL. Next, 10 kg is 50 mL/kg, so 10 x 50 = 500 mL. Remainder 15 kg, amount basically over 20 kg, is 20 mL/kg, so 15 x 20 = 300 mL, lastly add 1000 + 500 + 300 = 1,800 mL daily fluid requirement for 35 kg child.

A patient needs 30 mg of elemental iron daily. How many ml of ferrous sulfate oral drops, containing 75 mg/0.6 ml, should he take?

1.2mL

If a topical gel has 1,000 units of active ingredient per gram and decomposes at a rate of 50 units weekly, what is the half-life of the medication?

10 weeks Teaching Points This medication exhibits zero order kinetics. This is so because the decay is measured in units per time period vs. a percentage loss per time period. Half of the original 1,000 units is 500 units, 500 divided by 50 is 10 = 10 weeks.

The concentration of a solution of 10 mg per ml is the same as which of the following?

100mg per 10mL

The provider has ordered a dose of 150 mg of a drug. The original dose comes as a 10 ml vial labeled as 15 mg per ml. How many milliliters should be injected?

10mL Teaching Points Each ml contains 15 mg; hence 150 mg is 10 mL or 10 ml.

A patient is ordered 50 mg of gentamicin by intramuscular (IM) injection. The drug is available in 20 mg/5 mL. How many mL should the nurse administer?

12.5mL

A prescriber has ordered warfarin 3 mg on Monday, Wednesday, and Friday and on Tuesday, Thursday, Saturday, and Sunday, 1 mg. How many mg are taken each week?

13

How many grams does a 120 mL volume of liquid weigh if it has a specific gravity of 1.2?

144g Teaching Points The formula for specific gravity (SG) is the following: SG = weight of a substance/weight of an equal volume of water. Rearranging algebraically to isolate the variable you want: Weight = Volume X SG. Substitute values: Weight = (120)(1.2). The result is 144 grams.

The doctor has ordered 2 mg of a drug. The vial reads 4 mg in 2 mL. How much drug should be administered in milliliters?

1mL

A specific disease is found to have an incidence of 2% of the population per year. Individuals with the disease live on average 30 years. The incidence and mortality of the disease are unchanging. What is the estimated prevalence of the disease in the population?

2% Teaching Points Prevalence is the number of people who have a disease at a specific point in time (point prevalence) or during a time period (period prevalence). Prevalence can be calculated as prevalence = (total number of cases) / (population at risk) Prevalence can alternatively be calculated as prevalence = (incidence) x (duration of disease) If there is 2% incidence of a disease in the population and those with the disease live for 30 years then the prevalence is 60% = (2%/year) * (30 years).

The nurse is planning to administer insulin. Which of the following is not appropriate?

22-gauge, 1-inch needle

If a child is 11 years old, weighs 70 pounds, and the adult dose of a drug is 500 mg, what is the pediatric dose according to Young's rule?

240mg Teaching Points Young's rule is pediatric dose = adult dose X [age / (age+12)]. In this example: pediatric dose = 500 [11 / (11+12)]. Therefore: pediatric dose = 500 (11/23) = 500 X 0.48 = 240 mg. Recall that Young's rule uses age (a memory key, Young = age), while Clark's rule uses weight in pounds.

The dose is 200 mg and a 100 mg/mL vial is available. How many milliliters should the patient receive?

2mL

Mary has determined that one teaspoon of sugar does not help the medicine go down. As a result, she wants to determine if one tablespoon of sugar will help the medicine go down. If she only has a teaspoon, how many teaspoonfuls will it take to make one tablespoon?

3

An order comes in for 120 ml of 2% acetic acid solution. Your stock bottle is 50% acetic acid solution. How many ml of the 50% solution will be needed to fill your order?

4.8mL Teaching Points The quickest and most direct way to solve this problem is to use the dilution formula: initial strength (IS) X initial volume (IV) = final strength (FS) X final volume (FV). Substituting the values: (0.50)(x) = (0.02)(120); x = 4.8 mL. Another means to solve this would be to determine the number of grams of ingredient in the final product and set up a proportion to determine the amount in mL to obtain the same quantity of ingredient. The proportion setup is 2.4 grams/x mL = 50 grams/100 mL; both methods yield the answer 4.8 mL.

A syringe contains 10 mg of a drug in 1 mL of solution. How many micrograms of the drug would be administered if 0.5 mL of the solution is injected?

5,000

You have 250 mg of a drug in a fluid volume of 250 mL. The infusion time is four hours. How many mL are given per hour?

62.5 Teaching Points Rate = Volume/Time = 250 mL/4 hr = 62.5 mL/hr.

How is 4.50 written as an improper fraction?

9/2

You are asked to prepare 240 mL of drug X in a 1:20 (w/v) suspension. How much of your stock 1:8 suspension of drug X will be required to complete the order?

96mL Teaching Points This is a dilution problem, which uses the following formula: initial volume (IV) X initial strength (IS) = final volume (FV) X final strength (FS). First, convert the ratios to percentages for ease of calculation: 1:20 = 1/20 = 0.05 X 100 = 5%; 1:8 = 1/8 = 0.125 X 100 = 12.5%. You can use either decimalized or percentage numbers, but you must use the same form on both sides of the equation. Substitute: (12.5)(x) = (5)(240) Solve: 12.5x = 1,200; x = 96 mL.

Which of the following statements correctly describes rate of excretion of drugs undergoing first-order kinetics?

Constant portion is excreted Teaching Points First order kinetics are not a saturable kinetic. Constant portion is excreted or metabolized per half life. Constant amount is excreted in drugs that undergo zero order kinetics. Zero order kinetics is also called saturable kinetics.

Medication administration finds its basis in the decimal system. Safe practitioners must be able to read and fully understand decimals. One important concept to remember involves the knowledge that a decimal is which of the following?

Fraction that has a denominator that involves a power of ten Teaching Points The decimal or numerical system has a base of ten and is represented by powers of ten. In a fraction, the numerator denotes equal parts, and the denominator indicates how many of those parts are needed to make up a unit. In 1/4, 1 is the numerator, and the denominator is 4. As an example, 0.02 is the same as 2/100ths and 0.2 is the same as 2/10ths. It is important to include a zero before the decimal if the number is less than one. Use 0.2 rather than .2, which requires a leading zero. Never have any zeros at the end of a decimal. Use 0.2 rather than 0.20 because a trailing zero is not required.

A child presents with a two-day history of crying intermittently, fever, and pulling at the right ear. A diagnosis of otitis media made and a prescription for azithromycin 250 mg PO daily for three days provided. Measured weight is 46 pounds. The safe dose amount is 10 mg/kg/day according to the latest reference guide. Does this prescribed dose fall within the safe dosing guidelines?

No, the dose is not within the safe dosing guidelines Teaching Points First, change pounds to kilograms by dividing 46 by 2.2, since 1 kg = 2.2 lbs. 46/2.2 = 20.9 kg or 21 kg. Safe dose is 10 mg/kg/day, so 21 kg x 10 mg/kg = 210 mg/day. The prescribed dose is 250 mg per day, over the 210 mg daily safe dose, so no the treatment is not safe, and you must notify the provider.

Which of the following has a classic type of first order kinetics?

Radioactive decay Teaching Points Radioactive decay undergoes first order kinetics. A constant portion rather than a constant amount degrades per half life. There will always be some amount of radioactive substance left in the body even though it may be insignificant.