Pharmacy Calculations Guide
Course: Pharmacy Calculations (PHA 201)
Topic: Dosage & Compounding Calculations
Author: Compiled Notes
Table of Contents
1. Introduction
2. Key Definitions
3. Main Concepts
- Ratio & Proportion
- Percentage Strengths
- Dilutions
- Dosage Calculations
- IV Infusion Calculations
4. Diagrams/Charts
5. Case Examples
6. Summary / Key Takeaways
7. Practice Questions
1. Introduction
Pharmacy calculations are essential for accurate drug dispensing, compounding, and patient
safety. This guide simplifies the most common calculation methods required in exams and practice.
2. Key Definitions
Term Definition Example
Dose Quantity of drug taken at one time 500 mg paracetamol tablet
Concentration Amount of drug in a given volume 5% w/v = 5 g in 100 mL
Dilution Reducing concentration of a solution Mixing 10 mL stock + 90 mL water
Infusion Rate Volume delivered per unit time 60 mL/hour
3. Main Concepts
Ratio & Proportion
Used for dosage calculations. Formula: Dose required = (Prescribed dose / Available dose) ×
Available quantity. Example: Doctor prescribes 250 mg, pharmacy has 500 mg/5 mL suspension →
(250/500)×5 = 2.5 mL.
Percentage Strengths
Types: %w/v, %w/w, %v/v. Example: Prepare 250 mL of 10% w/v NaCl → 10 g × (250/100) = 25 g
NaCl.
Course: Pharmacy Calculations (PHA 201)
Topic: Dosage & Compounding Calculations
Author: Compiled Notes
Table of Contents
1. Introduction
2. Key Definitions
3. Main Concepts
- Ratio & Proportion
- Percentage Strengths
- Dilutions
- Dosage Calculations
- IV Infusion Calculations
4. Diagrams/Charts
5. Case Examples
6. Summary / Key Takeaways
7. Practice Questions
1. Introduction
Pharmacy calculations are essential for accurate drug dispensing, compounding, and patient
safety. This guide simplifies the most common calculation methods required in exams and practice.
2. Key Definitions
Term Definition Example
Dose Quantity of drug taken at one time 500 mg paracetamol tablet
Concentration Amount of drug in a given volume 5% w/v = 5 g in 100 mL
Dilution Reducing concentration of a solution Mixing 10 mL stock + 90 mL water
Infusion Rate Volume delivered per unit time 60 mL/hour
3. Main Concepts
Ratio & Proportion
Used for dosage calculations. Formula: Dose required = (Prescribed dose / Available dose) ×
Available quantity. Example: Doctor prescribes 250 mg, pharmacy has 500 mg/5 mL suspension →
(250/500)×5 = 2.5 mL.
Percentage Strengths
Types: %w/v, %w/w, %v/v. Example: Prepare 250 mL of 10% w/v NaCl → 10 g × (250/100) = 25 g
NaCl.
