# Pharmaceutical Calculation for Pharm D Students

PharmD is a professional pharmacy degree similar to a Doctor of Medicine (MD) or Doctor of Dental Surgery (DDS). As a doctorate, it increasing the responsibilities of pharmacists have in health care systems.

Pharmaceutical calculation is a core part of any pharmacy degree, especially for Pharm D degree. Pharm D students must learn about doses, concentration, and biopharmaceutics parameters.

The use of calculations in pharmacy is varied and broad-based. It encompasses calculations performed by pharmacists in traditional as well as in specialized practice settings and within operational and research areas in industry, academia, and government organization.

#### Success in performing pharmaceutical calculations is based on the:

• understanding of the purpose or goal of the problem;
• assessment of the arithmetic process required to reach the goal; and,
• implementation of the correct arithmetic manipulations.

This initial article is intended to remind the students of some previously learned mathematics. Most students likely will progress rapidly through this article.

#### Dosage Calculation Conversion Chart

• 1 kg = 2.2 lb
• 1 lb = 16 oz
• 1 tsp = 5 mL
• 1 gallon = 4 quart
• 1 L = 1,000 mL
• 1 kg = 1,000 g
• 1 oz = 30 mL = 2 tbsp
• 8 oz = 240 mL = 1 glass
• 1 g = 1,000 mg
• 1 inch = 2.54 cm
• 1 mg = 1,000 mcg
• 1 cm = 10 mm
• 1 cup = 8 fl oz
• 1 tbsp = 15 mL
• 1 pint = 2 cups
• 12 inches = 1 foot
• 1 L = 1.057 qt
• 1 tbsp = 3 tsp
• 60 minute = 1 hour
• 1 cc = 1 mL
• 2 pints = 1 qt
• 1 pt = 500 mL = 16 oz
• 1 tsp = 60 gtt
• 1 oz = 30 mL
• 4 oz = 120 mL (Casey, 2018)

#### Prescription Abbreviations List

• po: by mouth (or orally)
• susp: suspension
• pm: as needed
• tab: tablet
• IM: intramuscularly
• IV: intravenous
• cap: capsule
• q: every
• bid: twice a day
• tid: three times a day
• qid: four times a day
• qhs: before bed
• ac: before meals
• pc: after meals
• prn: as needed

#### Pharmaceutical Calculation Example

Practice 1:

If the adult dose of a medication is 2 teaspoonsful (tsp.), calculate the dose for a child if it is 1/4 of the adult dose.

1/4 x 2 tsp. =  2/4 = 1/2 tsp.

Practce 2:

If a child’s dose of a cough syrup is 3⁄4 teaspoonful and represents 1⁄4 of the adult dose, calculate the corresponding adult dose.

3/4 tsp. ÷ 1/4 = 3/4 tsp. x 4/1 = (3x4) ÷(4x1) tsp. = 12÷4 tsp. = 3 tsp.

Practice 3:

Order: Doxycycline 100 mg po daily

Supply: Doxycycline 0.2 g (200 mg) per tablet

Give: 100/200 x 1 tablet = 1/2 tablet

#### SOME ARITHMETIC SYMBOLS USED IN PHARMACY

Related: Pharm D Syllabus in USA