Accurate dosage calculation begins with understanding units of measurement. This lesson reviews the systems used in medication measurement and the metric conversions nurses most often need.
The apothecary system is an older system that includes grains, drams, scruples, and minims. It may use Roman numerals and is difficult to interpret safely. It is seldom used; if an order uses apothecary units, clarify or convert it with an appropriate reference and collaborate with a pharmacist as needed.
All flashcards
Desired Over Have formula
Calculate the amount to administer with D/H×Q=X, where D is the desired dose, H is the available dose, and Q is its associated quantity.
Medication strength
The amount of drug in a stated quantity, such as 125 mg per 5 mL or 2.5 mg per tablet.
Dimensional analysis
A calculation method that arranges conversion factors so unwanted units cancel and the requested unit remains.
Reconstitution
Preparation of a medication powder by adding liquid according to product-specific directions; use the resulting concentration.
Modified-release medication
Extended-release, sustained-release, controlled-release, or enteric-coated tablets should not be split or crushed unless product-specific guidance permits it.
Quiz questions
When checking a medication label against an order, what should be verified about the medication supplied?Answer: That the supplied medication matches the medication ordered.
An order calls for 250 mg, and the available liquid contains 125 mg per 5 mL. How much liquid supplies the ordered dose?Answer: 10 mL.
A dose is prescribed at 10 mg/kg for a client weighing 50 kg. What is the calculated dose?Answer: 500 mg.
In dimensional analysis, how should conversion factors be arranged?Answer: So unwanted units cancel and the requested unit remains.
Unless product-specific guidance permits it, how should extended-release tablets be handled?Answer: Do not split or crush them.
Based on Pharmacology for Nurses by Tina Barbour-Taylor, Leah Mueller (Sabato), Donna Paris, Dorie Weaver (OpenStax), licensed CC BY 4.0. Adapted into a summary, flashcards and quizzes.