Download Pharmaceutics 1 Unit-2 Notes PDF. This resource covers pharmaceutical calculations (weights, measures, percentage solutions, alligation, proof spirit, isotonic solutions), powders (classification, preparation), and liquid dosage forms (excipients, solubility enhancement). Essential for pharmacy students!
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Pharmaceutics 1 Unit-2: Pharmaceutical Calculations, Powders, and Liquid Dosage Forms
Pharmaceutics 1 Unit-2 is a critical module covering essential calculations, the preparation and properties of powders, and the formulation of liquid dosage forms. Mastering these topics is fundamental to a successful career in pharmacy. This guide explores each area in detail, providing a comprehensive understanding of the key concepts and applications.
I. Pharmaceutical Calculations
Accurate pharmaceutical calculations are essential for preparing and dispensing medications. This section covers weights and measures, percentage solutions, alligation, proof spirit, and isotonic solutions.
- Weights and Measures - Imperial & Metric System:
- Understanding the units of measurement in both the Imperial and Metric systems is crucial.
- Imperial System: Inches, feet, pounds, ounces, gallons.
- Metric System: Grams (g), liters (L), meters (m).
- Conversion Factors:
- 1 inch = 2.54 cm
- 1 pound = 453.592 grams
- 1 fluid ounce = 29.574 milliliters
- Calculations Involving Percentage Solutions:
- Percentage solutions express the concentration of a solute in a solution.
- Weight in Volume (w/v): Grams of solute per 100 mL of solution.
- Volume in Volume (v/v): Milliliters of solute per 100 mL of solution.
- Weight in Weight (w/w): Grams of solute per 100 grams of solution.
- Example: How many grams of NaCl are needed to prepare 500 mL of a 0.9% w/v solution?
- 0.9 g NaCl / 100 mL solution = x g NaCl / 500 mL solution
- x = (0.9 × 500) / 100 = 4.5 grams of NaCl
- Alligation:
- A method used to calculate the proportions of two or more solutions of known concentrations needed to prepare a solution of a desired concentration.
- Alligation Medial: Used to calculate the average percentage strength of a mixture.
- Alligation Alternate: Used to determine the quantities of two or more components needed to prepare a mixture of desired strength.
- Example: How many parts of 10% and 25% solutions are needed to prepare a 15% solution?
- Draw the alligation square.
- Subtract diagonally: (25-15) = 10 parts of 10% solution and (15-10) = 5 parts of 25% solution.
- Proof Spirit:
- A measure of the ethanol content of an alcoholic beverage or pharmaceutical preparation.
- Proof Strength: Twice the percentage of alcohol by volume.
- Example: 70% alcohol by volume is 140 proof.
- Calculations: Converting between percentage strength and proof strength.
- Isotonic Solutions Based on Freezing Point and Molecular Weight:
- Isotonic solutions have the same osmotic pressure as body fluids, preventing cell damage.
- Freezing Point Depression: Isotonic solutions have a freezing point of -0.52°C.
- Sodium Chloride Equivalent (E-value): The amount of sodium chloride that produces the same osmotic effect as 1 gram of the drug.
- Molecular Weight Method: Using the molecular weight and dissociation factor of the drug to calculate isotonicity.
II. Powders
Powders are solid dosage forms consisting of a mixture of finely divided drugs and/or chemicals. They are versatile and can be used for various routes of administration.
- Definition: Solid dosage form consisting of a mixture of finely divided drugs and/or chemicals in a dry form.
- Classification:
- Simple Powders: Containing only one medicinal substance.
- Compound Powders: Containing two or more medicinal substances.
- Dusting Powders: Applied externally to the skin.
- Effervescent Powders: Containing an acid and a base that react in water to release carbon dioxide.
- Advantages:
- Flexibility in compounding.
- Relatively good stability.
- Rapid dispersion.
- Easy to swallow.
- Disadvantages:
- Inaccurate dosing.
- Unpleasant taste.
- Handling difficulties.
- Deliquescence and hygroscopicity.
- Simple & Compound Powders – Official Preparations:
- Understanding the formulas and preparation methods for simple and compound powders listed in official pharmacopoeias.
- Dusting Powders:
- Used for external application to protect, lubricate, or absorb moisture. Must be sterile and free from irritants.
- Effervescent, Efflorescent, and Hygroscopic Powders:
- Effervescent Powders: Contain an acid and a base that react in the presence of water to release carbon dioxide.
- Efflorescent Powders: Substances that lose their water of hydration and become powdery.
- Hygroscopic Powders: Substances that absorb moisture from the air.
- Eutectic Mixtures:
- Mixtures of two or more substances that liquefy when mixed together at room temperature. Managed by adding inert diluents.
- Geometric Dilutions:
- A technique used to ensure uniform distribution of potent drugs in a powder mixture.
- Involves gradually adding the potent drug to a larger quantity of diluent, mixing thoroughly after each addition.
III. Liquid Dosage Forms
Liquid dosage forms are preparations in which the drug is dissolved or dispersed in a liquid vehicle. They are often preferred for patients who have difficulty swallowing solid dosage forms.
- Advantages of Liquid Dosage Forms:
- Easy to swallow.
- Faster absorption.
- Flexibility in dosing.
- Disadvantages of Liquid Dosage Forms:
- Bulky.
- Stability issues.
- Taste masking challenges.
- Accurate dosing requires measuring devices.
- Excipients Used in Formulation of Liquid Dosage Forms:
- Solvents: Water, alcohol, glycerin, propylene glycol.
- Co-solvents: Used to increase the solubility of poorly soluble drugs.
- Buffers: Maintain the pH of the formulation.
- Preservatives: Prevent microbial growth.
- Sweeteners: Improve the taste.
- Flavoring agents: Mask the unpleasant taste of the drug.
- Coloring agents: Enhance the appearance of the formulation.
- Viscosity enhancers: Increase the viscosity of the formulation.
- Antioxidants: Prevent oxidation of the drug.
- Solubility Enhancement Techniques:
- Co-solvency: Using a mixture of solvents to increase the solubility of the drug.
- Complexation: Forming complexes with cyclodextrins or other complexing agents to increase solubility.
- Micronization: Reducing the particle size of the drug to increase its surface area and dissolution rate.
- Solid dispersion: Dispersing the drug in a water-soluble carrier.
- pH adjustment: Adjusting the pH of the formulation to increase the solubility of acidic or basic drugs.
- Solubilization with surfactants: Using surfactants to form micelles that can solubilize the drug.
Conclusion
Pharmaceutics 1 Unit-2 provides a foundational understanding of pharmaceutical calculations, powders, and liquid dosage forms. By mastering these concepts, pharmacy students can develop the skills necessary to formulate safe, effective, and patient-friendly medications. Proper calculations, careful selection of excipients, and appropriate preparation techniques are crucial for ensuring the quality and efficacy of pharmaceutical products.
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