NAPLEX (North American Pharmacist Licensure Examination) Practice Exam

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Ace your North American Pharmacist Licensure Examination (NAPLEX) with our comprehensive practice test. Features include interactive flashcards, multiple-choice questions, with detailed hints and explanations. Fast-track your pharmacy career today!

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What formula represents the calculation for Isotonicity (E-value)?

Q1 x Q2 = C1 x C2
Wt of substance / MW * 1000
E = (58.5)(i) / (MW of drug)(1.8)
g / MW

The correct answer is: E = (58.5)(i) / (MW of drug)(1.8)

The correct formula for calculating isotonicity (E-value) is E = (58.5)(i) / (MW of drug)(1.8). This formula takes into account factors such as the number of ions formed when the drug dissolves (i.e., the Van't Hoff factor), the molecular weight of the drug, and a constant value to ensure isotonicity when preparing pharmaceutical solutions. Option A (Q1 x Q2 = C1 x C2) represents the dilution equation, which is not related to isotonicity calculations. Option B (Wt of substance / MW * 1000) is a formula for calculating the number of equivalents of a substance, not for isotonicity. Option D (g / MW) is a formula for calculating the number of moles of a substance, which is not used for determining isotonicity. Therefore, the correct formula for calculating isotonicity is E = (58.5)(i) / (MW of drug)(1.8), making option C the correct answer.