PharmaCalc - Pharmacy Concepts

PharmaCalc Pro | Clinical & Pharmaceutical Suite

PharmaCalc Clinical & Compounding

Validated Pharmaceutical Calculation Suite (Education purposes only)

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Clinical Verification

Formulas comply with USP, FDA, and BNF clinical dispensing standards.

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Body Surface Area (BSA) & Dose Calculation

Compute patient BSA using Mosteller & Du Bois equations alongside mg/kg and mg/m² dosing regimens.

Body Surface Area

Mosteller & Du Bois

Height

Weight

Mosteller: √((Height [cm] × Weight [kg]) / 3600)

Du Bois: 0.007184 × Ht(cm)^0.725 × Wt(kg)^0.425

Mosteller BSA 1.82 m²

Du Bois BSA 1.81 m²

Dose Calculation Mode

Prescribed Dose (mg/kg/day)

mg/kg/day

Divided Doses Frequency

Stock Liquid Strength (Optional)

mg/5mL

Total Daily Dose 1,050.00 mg

Per Individual Dose 350.00 mg

Equivalent Volume per dose (mg/5mL): 7.00 mL

Body Mass Index (BMI) & Ideal Body Weight (IBW)

Calculate BMI classification, Devine IBW, and Adjusted Body Weight (AdjBW) for clinical pharmacokinetics.

Patient Parameters

Biological Sex

Height

Actual Weight (TBW)

Obesity Adjustment Factor (Typically 0.4 or 0.3) AdjBW = IBW + 0.40 × (Actual Weight - IBW)

Anthropometric Summary Overweight

Body Mass Index (BMI)

Weight (kg) / Height (m)²

28.7 kg/m²

Devine Ideal Body Weight (IBW)

Base 50kg (M) / 45.5kg (F) + 2.3kg/inch > 5ft

70.4 kg

Adjusted Body Weight (AdjBW)

Recommended when Actual Wt > 120% of IBW

77.4 kg

Clinical Note: Patient weight exceeds 120% of Ideal Body Weight (125%). Aminoglycosides and Vancomycin typically require Adjusted Body Weight (AdjBW).

Pediatric Historical Dosing Formulas

Calculate estimated pediatric fractions from adult doses using Clark's, Young's, and Fried's rules.

Standard Parameters

Standard Adult Dose

Child's Weight

Clark's rule requires weight in lbs.

Child's Age (Years) Young's rule is for children > 1 to 12 years.

Infant Age (Months) Fried's rule applies up to 24 months.

Clark's Rule

Weight

(Weight in lbs / 150) × Adult Dose

Estimated Dose:

100.00

20.0% of adult dose

Young's Rule

Age (Yrs)

(Age / (Age + 12)) × Adult Dose

Estimated Dose:

147.06

29.4% of adult dose

Fried's Rule

Infants

(Age in mos / 150) × Adult Dose

Estimated Dose:

26.67

5.3% of adult dose

Clinical Caution: Young's, Clark's, and Fried's rules are historic empirical estimates. Modern pediatric therapeutics dictates weight-based (mg/kg) or BSA-based (mg/m²) dosing according to validated pediatric drug labeling.

Solution Chemistry & Pharmaceutical Compounding

Molarity, normality, equivalent weights, dilution calculations (C1V1 = C2V2), and percentage formulations.

Molarity (M) & Normality (N) N = M × Valence

Mass of Solute (g)

Molecular Weight (g/mol)

Total Solution Volume

Valence Factor (n-factor)

Molarity (M) 0.200 M moles/L

Normality (N) 0.200 N Eq/L

Dilution (C₁ × V₁ = C₂ × V₂) Target: V1 or C2

Stock Conc. (C₁)

Desired Conc. (C₂)

Final Desired Volume (V₂)

Stock Solute Volume (V₁) Needed 71.43 mL

Diluent Volume to Add 428.57 mL

Add 71.43 mL stock to ~400 mL diluent and bring quantity sufficient (q.s.) to 500 mL.

Percentage Formulations (% w/v, % v/v, % w/w) 1% w/v = 1g / 100mL = 10 mg/mL

Type of Percentage

Percentage Strength (%)

Total Target Preparation

Active Solute Required

5.00 g

Concentration in mg/mL

25.0 mg/mL

Ratio Strength (1 in X)

1 : 40

Alligation Alternate (Pearson's Square)

Determine proportional quantities to compound a target strength from two different stock concentrations.

Concentrations & Desired Quantity

Higher Concentration Stock (C_high %)

Lower Concentration Stock or Diluent (C_low %)

Desired Target Concentration (C_target %)

Total Desired Quantity (mL or g)

Pearson Square Compounding Schema

70% ╲ ╱ 20 parts

30%

10% ╱ ╲ 40 parts

Total Parts: 60

Higher Strength Solute (70%): 200.00 mL/g

Lower Strength Solute (10%): 400.00 mL/g

pH, pKa & Drug Ionization Degree

Henderson-Hasselbalch buffer equilibrium and gastrointestinal absorption ionization predictions.

Henderson-Hasselbalch Buffer pH pH = pKa + log([A⁻]/[HA])

Dissociation Constant (pKa)

Base [A⁻] Concentration

Acid [HA] Concentration

Calculated Buffer Solution pH 5.06

log([A-]/[HA]) +0.301

Percentage Drug Ionization Calculator Bioavailability Parameter

Drug Pharmacological Chemistry

Drug pKa

Medium pH (e.g., Stomach 1.5, Plasma 7.4)

Presets:

Ionized Fraction (Polar) 99.99%

Unionized (Lipophilic / Absorbable) 0.01%

Only un-ionized drug species readily permeate lipid membranes through passive diffusion.

Renal Function: Cockcroft-Gault Creatinine Clearance

Gold standard estimate for renal dose adjustment according to drug monographs.

Clinical Inputs CG-CrCl Formula

Sex assigned at birth

Patient Age (Years)

Body Weight (kg)

Serum Creatinine (SCr)

Cockcroft-Gault Equation: CrCl = [ (140 - Age) × Weight (kg) ] / [ 72 × Serum Creatinine (mg/dL) ] (× 0.85 if Female)

Estimated Creatinine Clearance Stage 2: Mild

Estimated CrCl Rate 62.5 mL / minute

> 90 mL/min: Normal renal filtration

60 - 89 mL/min: Mild renal impairment

30 - 59 mL/min: Moderate impairment (Dose adjustment common)

15 - 29 mL/min: Severe renal impairment

< 15 mL/min: Kidney failure (ESRD / Dialysis)

Note: Use ideal body weight (IBW) if actual weight > 120% of IBW to avoid overestimation of clearance in obese patients.

Designed for pharmacists, clinical students, and pharmacy tech compounding training.

Strictly for educational and calculation verification purposes.