Pharmacy Calculations Workshop

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Questions and Answers

When is the Michaelis-Menten equation expected to demonstrate first-order kinetics?

  • When substrate concentration [S] approaches the mean μ.
  • When substrate concentration [S] fluctuates randomly around the mean μ.
  • When substrate concentration [S] is significantly higher than the mean μ.
  • When substrate concentration [S] is significantly lower than the mean μ. (correct)

The 68-95-99.7 rule describes the distribution of data. What percentage of data falls within 2 standard deviations from the mean?

  • 99.7%
  • 68%
  • 100%
  • 95% (correct)

What does a false positive in a test indicate?

  • Incorrectly identified negative condition.
  • Correctly identified positive condition.
  • Correctly identified negative condition.
  • Incorrectly identified positive condition. (correct)

What is the equivalent weight of 1 grain in milligrams?

<p>65 mg (B)</p> Signup and view all the answers

How many milliliters are there in one pint?

<p>480 ml (B)</p> Signup and view all the answers

Which of the following is a common error type mentioned in the context of test outcomes?

<p>Type I Error (D)</p> Signup and view all the answers

What does the term 'pKa' refer to in the provided formula for calculating pH?

<p>The acid dissociation constant (C)</p> Signup and view all the answers

When calculating the pH using the formula $pH = pKa + log\left(\frac{[Salt]}{[Acid]}\right)$, what does a pH – pKa difference of 1 correspond to in terms of salt and acid ratio?

<p>90 : 10 (C)</p> Signup and view all the answers

How is the volume of isotonic solution that can be prepared from a given weight of drug calculated?

<p>Using the formula $V = W \times E \times 111.1$ (C)</p> Signup and view all the answers

In the example provided for isotonicity, how much sodium chloride is required to prepare a 100 ml solution of a 1% apomorphine hydrochloride solution?

<p>15.55 ml (B)</p> Signup and view all the answers

If the pKb of ephedrine is 4.56, what can be inferred about the relationship between its pKa and pKb?

<p>pKa is higher than 4.56 (B)</p> Signup and view all the answers

What would be the calculated pH of a solution containing 0.5 moles of ephedrine and 0.05 moles of ephedrine HCl using the provided formula?

<p>Approximately 8.05 (A)</p> Signup and view all the answers

What does the sodium chloride equivalent value (E) indicate in the context of isotonic solutions?

<p>The weight of sodium needed to achieve isotonicity (B)</p> Signup and view all the answers

In the formula provided, what represents the 'Salt' component when calculating the pH?

<p>The base form of a weak acid (C)</p> Signup and view all the answers

What does a 0.5 molar solution represent?

<p>0.5 moles of solute in 1 liter of solution (B)</p> Signup and view all the answers

Which of the following defines molality?

<p>The number of moles of solute in 1000 grams of solvent (D)</p> Signup and view all the answers

What is the dissociation value for CaCl2 in a weak solution?

<p>2.6 (C)</p> Signup and view all the answers

What is the freezing point depression caused by dissolving 1 g mol wt of any nonelectrolyte in 1000g of water?

<p>-1.86 ℃ (B)</p> Signup and view all the answers

To prepare an isotonic solution, how much NaCl is needed for a solution that has a freezing point depression of -0.52 ℃?

<p>0.52 g (A)</p> Signup and view all the answers

Which of the following is NOT true about normality (N)?

<p>It is measured in grams of solute per liter of solution. (A)</p> Signup and view all the answers

What is the freezing point depression of body fluids compared to the freezing point of 0.9% NaCl?

<p>-0.52 ℃ (B)</p> Signup and view all the answers

In preparing isotonic solutions, how is the amount of NaCl equivalent calculated?

<p>By calculating the mass difference between NaCl and other ingredients. (B)</p> Signup and view all the answers

What abbreviation indicates a drug should be taken three times a day?

<p>tid (C)</p> Signup and view all the answers

How does molarity differ from normality?

<p>Normality takes ion dissociation into account. (D)</p> Signup and view all the answers

Which formula is used to calculate the loading dose for an intravenous infusion?

<p>Loading Dose = 0.693 Vd / Clt (A)</p> Signup and view all the answers

What does the Michaelis–Menten equation describe in pharmacokinetics?

<p>The reaction rate as a function of substrate concentration (D)</p> Signup and view all the answers

What is the half-life formula used in pharmacokinetics?

<p>t1/2 = 0.693 Vd / Clt (A)</p> Signup and view all the answers

What is the purpose of Young's Rule in pediatric dosing?

<p>To estimate dosage based on age for children over 2 years. (C)</p> Signup and view all the answers

When administering a drug via IV infusion, how does the rate of accumulation compare to a single dose?

<p>The accumulation rate doubles the rate of a single dose if given at the same interval. (B)</p> Signup and view all the answers

What is the correct formula for calculating the half-life of a drug with a volume of distribution (Vd) and clearance (Cl)?

<p>$t_{1/2} = 0.693 \times \frac{Vd}{Cl}$ (A)</p> Signup and view all the answers

In an allegation problem, what is the definition of the term 'allegation'?

<p>A calculation involving mixing different concentrations to achieve a desired concentration. (A)</p> Signup and view all the answers

What is the significance of the elimination half-life in pharmacokinetics?

<p>It indicates how quickly a drug is cleared from the body. (A)</p> Signup and view all the answers

What is the appropriate calculation for a child's dosage based on Clark's Rule?

<p>Weight in pounds x adult dose / 150 lb (A)</p> Signup and view all the answers

When preparing a solution, what is meant by 'mEq'?

<p>Milliequivalents, a measure of solute concentration in a solution. (A)</p> Signup and view all the answers

Which of the following is true about the 0 order reaction?

<p>The rate of elimination is constant over time, irrespective of concentration. (D)</p> Signup and view all the answers

For a drug given via multiple dosing, what does the formula $R = e^{kT}$ represent?

<p>The rate of drug accumulation in the body. (D)</p> Signup and view all the answers

How would you prepare a 30% alcoholic elixir using a 70% and 20% alcoholic elixir?

<p>Use more of the 70% elixir than the 20% elixir. (D)</p> Signup and view all the answers

Flashcards

First-order reaction

A chemical reaction where the rate of reaction is directly proportional to the concentration of the reactant. The half-life of a first-order reaction is constant.

Zero-order reaction

A chemical reaction where the rate of reaction is independent of the concentration of the reactant. The half-life of a zero-order reaction is dependent on the initial concentration of the reactant.

Loading dose

The initial dose of medication given to rapidly achieve a therapeutic concentration in the blood.

Drug clearance (Cl)

The rate at which a drug is eliminated from the body.

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IV infusion

A method of drug administration where a continuous infusion of medication is given intravenously.

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Accumulation rate

The increase in drug concentration in the body with repeated doses.

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Fraction remaining in the body

The fraction of the drug remaining in the body after a dosage interval.

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Young's Rule

A formula used to calculate the dose of medication for children over 2 years of age.

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Clark's rule

A formula used to calculate the dose of medication for children aged 2-17 years.

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Fried's rule

A formula used to calculate the dose of medication for infants based on their weight.

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Normality (N)

The number of gram equivalent weights of solute present in 1 liter (1000 ml) of solution.

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Molarity (M)

The number of moles of solute dissolved in 1 liter (1000 ml) of solution.

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Molality (m)

The number of moles of solute dissolved in 1 kilogram of solvent.

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Isotonic Solution

A solution that has the same osmotic pressure as another solution, typically body fluids.

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Freezing Point Depression

The depression of the freezing point of a solution compared to the pure solvent.

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Dissociation Value (i)

The number of ions that a molecule dissociates into in solution, representing its relative contribution to osmotic pressure.

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Sodium Chloride Equivalents

A measure of the osmotic effect of a substance relative to sodium chloride.

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NaCl Equivalent Calculation

A calculation method used to convert the osmotic effect of a substance to an equivalent amount of NaCl.

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NaCl Equivalent of a Prescription Component

The amount of a specific ingredient in a solution that is equivalent to the osmotic effect of a certain amount of NaCl.

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Calculating NaCl Equivalents for Isotonic Solutions

The process of determining the amount of a specific ingredient (like a drug) that is equivalent to a certain amount of NaCl, to maintain isotonicity.

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Henderson-Hasselbalch equation

The Henderson-Hasselbalch equation relates the pH of a solution to the pKa of the acid and the ratio of the concentrations of the acid and its conjugate base. It is used to calculate the pH of buffer solutions and to understand the effects of adding acid or base to a buffer solution.

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Rule of Nines (Burns)

The rule of nines is a rule of thumb for estimating the percentage of the body surface area that has been burned. It is based on the assumption that the body can be divided into nine equal parts.

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pH of a buffer solution

The pH of a solution containing a weak acid and its conjugate base can be calculated using the Henderson-Hasselbalch equation. The ratio of the concentrations of the acid and its conjugate base determines the pH of the solution.

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NaCl Equivalent Value

The NaCl equivalent value is a measure of the relative ability of a drug to lower the freezing point of water, which is a property that determines its tonicity. It is used to calculate the amount of sodium chloride needed to adjust the tonicity of a drug solution.

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Drug Weight and Equivalent Value

The weight of a drug is the amount of drug in a specified volume of solution, and its equivalence value is based on how much a drug is 'equivalent' to sodium chloride in terms of effect on freezing point. This information can be used to calculate the volume of isotonic solution that can be prepared from a given weight of drug.

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Tonicity

The tonicity of a solution refers to its osmotic pressure, which is the pressure required to prevent water from moving across a semipermeable membrane. This is important in pharmacy because it can affect the absorption and distribution of drugs.

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Pharmaceutical Compounding

The process of compounding involves combining different ingredients to create a final pharmaceutical product. It often involves calculations to ensure the correct dosage and concentration of the ingredients.

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Dosage Calculations

Dosage calculations are essential for accurately calculating the amount of medication to be administered. It involves factors like patient weight, age, and the concentration of the medication.

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68-95-99.7 Rule

A statistical rule stating that approximately 68% of data falls within one standard deviation of the mean, 95% within two standard deviations, and 99.7% within three standard deviations.

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Equilibrium Assumption

The assumption that the rate of the reverse reaction in a reversible enzyme reaction is much faster than the rate of the forward reaction.

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Sensitivity

A measure of how well a test correctly identifies individuals with a condition.

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Specificity

A measure of how well a test correctly identifies individuals without a condition.

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Positive Predictive Value

The probability of a positive test result actually indicating the presence of the condition.

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Negative Predictive Value

The probability of a negative test result actually indicating the absence of the condition.

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Infusion Rate

The rate at which a drug is infused into the body, usually measured in milligrams per minute.

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Half-life

The time it takes for the concentration of a drug in the body to reduce by half.

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Rate Constant (k) for First-Order Reactions

The rate constant for a first-order reaction, which indicates how quickly the drug is being eliminated from the body. The higher the value, the faster the elimination.

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Volume of Distribution (Vd)

The volume of the fluid in which a drug is dissolved, often expressed in liters.

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Clearance (Cl)

The ability of the body to clear a drug from the system, measured in liters per hour.

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Steady State Concentration (Css)

The concentration of a drug in the blood at steady state, meaning the rate of drug administration is equal to the rate of elimination.

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Michaelis-Menten Equation

The equation that describes the relationship between the reaction rate (v) and the substrate concentration ([S]) for an enzyme-catalyzed reaction.

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Study Notes

Pharmacy Calculations Workshop

  • Workshop presented by Yuxin Qian, 090422
  • Topics covered include: formulas, solutions, compounding, dose-related calculations, pharmacokinetics, pharmacy financial assessment, and statistics.
  • Formulas will be provided in the examination booklets, and don't need to be memorized.
  • Examples of formulas from the PEBC information booklet (used in the EE exam) will be provided.
  • Formulas for calculating rate constants for 1st and 0th order reactions were shown.
  • pH calculations using pKa and pKb
  • Rule of nines for pH calculations was presented( I pH - pKa I = 1 ---- 90 : 10, I pH - pKa I = 2 ---- 99 : 1, I pH - pKa I = 3 ---- 99.9 : 0.1 ).
  • Calculations for preparing isotonic solutions, including dissociation values (i) for various solutions (NaCl, CaCl2).
  • Formulas for calculating inventory turnover, gross margin, net profit margin, price markup, elasticity.
  • Formulas for calculating normality, molarity, molality and their applications.
  • Formulas for calculating isotonic solutions, and their relation to freezing point depression
  • Procedures for compounding and dose administration were explained along with related abbreviations.
  • Formulas related to Pharmacokinetics, such as calculating loading dose, infusion rate, and steady-state concentration (Css) were covered.
  • Formulas for different reaction orders (zero, first, second, and nth order). Included Rate Laws, integrated rate laws, units of rate constant, linear plots, and half-lives.
  • Examples of questions and solution steps for various types of calculations were demonstrated (e.g. determining the pH of a solution , calculating the amount of NaCl needed for a solution, calculating rate of flow, calculating dosing rate).
  • Formulas for Calculating Mean, Median, Mode, Degree of freedom (DF), range
  • Standard deviation (SD), relative standard deviation (RSD), standard error of the mean (SEM).
  • Normal distribution (68-95-99.7 rule) and its practical implications.
  • Study types like case-control, cohort, cross-sectional, twin concordance, and adoption studies were defined and examples of study designs were highlighted.
  • Accuracy and precision definitions for data collection and measurement were presented.
  • Type I and II errors were explained along with their use in research.
  • t-test, ANOVA, and meta-analysis were discussed.
  • Calculator usage and key functions important for exam were explained.
  • Important conversions between different units of different systems (e.g. apothecary, avoirdupois)
  • Final tips and advice regarding the use of formulas and attentive calculations during the Workshop, and important considerations for the exam were discussed.

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