Pharmacy Formula Library

01 Pharmaceutics

Bulk Density

ρ_b = M / V_b

Mass of powder divided by its bulk volume.

Where:
M = mass of powder
V_b = bulk volume

Common unit: g/mL

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02 Pharmaceutics

Tapped Density

ρ_t = M / V_t

Mass of powder divided by its tapped volume.

Where:
M = mass of powder
V_t = tapped volume

Common unit: g/mL

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03 Pharmaceutics

Carr's Index

CI = [(ρ_t − ρ_b) / ρ_t] × 100

Indicates the compressibility characteristics of a powder.

ρ_t = tapped density
ρ_b = bulk density

Expressed as %

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04 Pharmaceutics

Hausner Ratio

HR = ρ_t / ρ_b

Ratio of tapped density to bulk density.

ρ_t = tapped density
ρ_b = bulk density

Dimensionless

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05 Pharmaceutics

Angle of Repose

tan θ = h / r

Describes the flow behavior of a powder.

h = height of powder cone
r = radius of powder cone

Usually reported in degrees

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06 Pharmaceutics

Percentage Yield

% Yield = (Actual Yield / Theoretical Yield) × 100

Compares actual product obtained with the theoretical amount.

Actual yield = amount obtained
Theoretical yield = expected amount

Expressed as %

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07 Pharmaceutics

Drug Loading

DL = (Drug in formulation / Total formulation weight) × 100

Represents the proportion of drug present in a formulation or carrier system.

Drug = amount of active drug
Total = total formulation amount

Expressed as %

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08 Pharmaceutics

Entrapment Efficiency

EE = [(Total Drug − Free Drug) / Total Drug] × 100

Indicates the fraction of drug successfully entrapped within a delivery system.

Total drug = total amount used
Free drug = unentrapped amount

Expressed as %

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09 Pharmaceutics

Swelling Index

SI = [(W_t − W₀) / W₀] × 100

Measures the increase in mass caused by liquid uptake.

W_t = weight after swelling
W₀ = initial weight

Expressed as %

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10 Pharmaceutics

Moisture Content

MC = [(Initial − Final) / Initial] × 100

Estimates the percentage mass lost during drying.

Initial = initial sample mass
Final = mass after drying

Expressed as %

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11 Calculations

Percentage Strength

% = (Amount of solute / Final amount) × 100

Expresses the concentration of a preparation as a percentage.

Amount = solute quantity
Final amount = final preparation quantity

%

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12 Calculations

Molarity

M = moles / volume (L)

Number of moles of solute present per litre of solution.

moles = amount of substance
volume = solution volume in litres

mol/L

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13 Calculations

Normality

N = equivalents / volume (L)

Concentration expressed as gram-equivalents per litre.

equivalents = gram-equivalents
volume = solution volume in litres

eq/L

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14 Calculations

Dilution

C₁V₁ = C₂V₂

Relates concentration and volume before and after dilution.

C₁ = initial concentration
V₁ = initial volume
C₂ = final concentration
V₂ = final volume

Depends on concentration system

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15 Calculations

Alligation

Ratio = (High − Desired) : (Desired − Low)

Determines the relative quantities of two strengths needed to obtain a desired strength.

Low = lower concentration
High = higher concentration
Desired = target concentration

Ratio

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16 Calculations

Ratio Strength

% = (1 / Ratio) × 100

Converts ratio strength into percentage strength.

Ratio is commonly expressed as 1:X

%

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17 Calculations

Milliequivalents

mEq = mmol × Valence

Relates millimoles to milliequivalents using ionic valence.

mmol = millimoles
Valence = ionic charge

mEq

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18 Calculations

Millimoles

mmol = mg / Molecular Weight

Converts mass into amount of substance in millimoles when units are compatible.

mg = mass in milligrams
Molecular Weight = g/mol

mmol

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19 Clinical

Body Surface Area

BSA = √[(Height × Weight) / 3600]

Mosteller equation for estimating body surface area.

Height = cm
Weight = kg

m²

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20 Clinical

Dose

Dose = Concentration × Volume

Basic relationship between dose, concentration and volume.

Concentration = amount per volume
Volume = administered volume

Depends on input units

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21 Clinical

Infusion Rate

Rate = Volume / Time

Calculates the rate required to deliver a specified volume over a specified period.

Volume = total infusion volume
Time = infusion duration

mL/hour

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22 Clinical

Drops per Minute

gtt/min = (Volume × Drop Factor) / Time

Calculates manual infusion rate when a drop factor is known.

Volume = mL
Drop factor = drops/mL
Time = minutes

drops/min

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23 Tablet

Friability

% F = [(W₀ − W₁) / W₀] × 100

Calculates percentage weight loss after a friability test.

W₀ = initial weight
W₁ = final weight

Expressed as %

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24 Tablet

Drug Content

% Drug Content = (Measured / Label Claim) × 100

Expresses measured drug amount relative to the stated label claim.

Measured = experimentally determined amount
Label claim = stated amount

%

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25 Tablet

Dissolution %

% Release = (Amount Released / Label Amount) × 100

Expresses the amount of drug released relative to the labeled drug amount.

Amount released = calculated drug released
Label amount = labeled drug quantity

%

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