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TL;DR

Dilution Calculations: C1V1 = C2V2 formula for determining volumes needed when diluting concentrated solutions to desired concentrations.

By Valenke Exam Prep Team·Last updated 2026-06-02

Dilution Calculations

PTCBMEDICAL ASSISTANT

Definition

C1V1 = C2V2 formula for determining volumes needed when diluting concentrated solutions to desired concentrations.

Practical Example

Pharmacy Calculation Example: dilution

Formula: C1V1 = C2V2

Worked example: Dilute 70% alcohol to 30%: (70)(V1) = (30)(500mL), V1 = 214.3 mL

Exam Focus Areas

On the Ptcb, Medical Assistant exam(s), questions about dilution calculations typically test:

  1. Mathematical calculations: dosage, days supply, dilutions, and compounding
  2. Drug interactions and contraindications that affect patient safety
  3. Drug classification, mechanism of action, and common side effects
  4. Federal and state regulations governing practice

Historical Context

Pharmacy regulation in the U.S. began with the Pure Food and Drug Act of 1906. The Federal Food, Drug, and Cosmetic Act of 1938 required proof of safety. The 1962 Kefauver-Harris Amendment added efficacy requirements. Understanding dilution calculations within this regulatory history helps pharmacy technicians appreciate why current standards exist, as each major regulation was prompted by a public health crisis.

Step-by-Step Procedure

C1V1 = C2V2 formula for determining volumes needed when diluting concentrated solutions to desired concentrations. Dilution calculations tested on PTCB and MA exams.

Related drug class: Statins includes atorvastatin, rosuvastatin, simvastatin. Mechanism: HMG-CoA reductase inhibitors, decrease hepatic cholesterol synthesis, upregulate LDL receptors.

Why It Matters

Dilution calculations tested on PTCB and MA exams.

Related Terms

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Frequently Asked Questions

What drug interactions should be monitored for dilution calculations?
For dilution calculations: Fluoroquinolones (ciprofloxacin, levofloxacin, moxifloxacin): Tendon rupture (Achilles); QT prolongation; C. diff risk; Avoid with antacids (chelation). Always check for drug interactions before dispensing.
What calculations are involved in dilution calculations?
For dilution calculations: alligation: Parts of each concentration to reach desired concentration. Example: Mix 10% and 2% to get 5%: high minus desired = 5 parts of 2%, desired minus low = 3 parts of 10%.
What sig codes are commonly seen with dilution calculations prescriptions?
For dilution calculations: BID = twice daily, TOP = topically, AU = both ears, TID = three times daily, QD = once daily.