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Questions and Answers

What is the primary reason water is the most commonly used solvent in pharmaceutical preparations?

It's always sterile.

It's the cheapest solvent available.

It has a strong flavor.

It dissolves a wide variety of materials. (correct)

Which type of water is unsuitable for most pharmaceutical preparations due to potential chemical incompatibilities?

Sterile Water for Injection

Tap water (correct)

Bacteriostatic Water

Purified Water

What is the maximum residue percentage allowed in Purified Water, USP?

0.0001%

0.01%

0.1%

0.001% (correct)

Which of the following is NOT a method used to obtain Purified Water?

Filtration Signup and view all the answers

What characterizes Bacteriostatic Water for Injection?

Is sterile and contains an antimicrobial agent. Signup and view all the answers

Which of the following uses is appropriate for tap water in pharmaceutical settings?

Washing and equipment cleaning. Signup and view all the answers

Which statement about naturally occurring water is correct?

It contains varying amounts of inorganic salts and microorganisms. Signup and view all the answers

Which of the following describes the composition of tap water?

Contains less than 0.1% total solids. Signup and view all the answers

Why must the initial 10% to 20% of the distillate be discarded during distillation?

It contains volatile substances commonly found in urban drinking water. Signup and view all the answers

What is a benefit of ion exchange demineralization over distillation?

It eliminates the need for heat, reducing costs. Signup and view all the answers

In reverse osmosis, what describes the movement of water through the membrane?

Water flows from a more concentrated to a less concentrated solution. Signup and view all the answers

What type of contaminants can ultrafiltration remove?

Bacteria and large particulates. Signup and view all the answers

What is the primary function of cation exchangers in ion exchange systems?

To replace cations in solution with hydrogen ions from the resin. Signup and view all the answers

What happens to the remaining water in reverse osmosis after passing through the membrane?

It is concentrated and carries away the concentrated contaminants. Signup and view all the answers

Which resin type is utilized to remove anions from a solution?

Anion exchangers. Signup and view all the answers

What is a characteristic of the reverse osmosis process compared to regular osmosis?

It flows from a more concentrated solution to a less concentrated solution. Signup and view all the answers

Study Notes

Pharmaceutical Technology I - 3rd Stage

Solvent used in pharmaceutical preparations and oral solutions
Water is the most widely used solvent for pharmaceutical products due to lack of toxicity, physiological compatibility, and its ability to dissolve a wide range of materials
Naturally occurring water contains dissolved inorganic salts (sodium, potassium, calcium, magnesium, and iron), chlorides, sulfates, bicarbonates, dissolved and undissolved organic matter, and microorganisms.

Types of Pharmaceutical Water

Tap Water/Drinking Water/Potable Water: Contains less than 0.1% total solids; clear, colorless, odorless, and neutral or slightly acidic/alkaline; unsuitable for most pharmaceutical preparations due to potential chemical incompatibilities (precipitation, discoloration, effervescence). Used for washing, extracting crude vegetable drugs, and preparing some external use products; can be used economically for cleaning machinery.
Purified Water, USP: Contains fewer solid impurities than tap water, with a maximum 0.001% residue; used for preparing aqueous dosage forms (except parenteral). Obtained through distillation, ion exchange, and reverse osmosis.
Sterile Water for Injection, USP: Sterile, pyrogen-free, packaged in single units (less than 1 litre); used in injection preparation.
Bacteriostatic Water for Injection, USP: Sterile/pyrogen-free water with antimicrobial agents (SWFI); used in multiple-dosing injections.

Distillation Method

Discarding the First Portion of Distillate: Initial 10-20% discarded due to volatile substances commonly found in urban drinking water.
Discarding the Last Portion of Water: Final 10% discarded because the remaining solid impurities can decompose into volatile substances, contaminating the distillate.

Ion Exchange Demineralizer

Advantages over Distillation: Eliminates the need for heat, simpler equipment, minimal maintenance, and more mobile facility.
Ion Exchange Equipment: Water is passed through columns containing cation and anion exchangers. Exchangers are water-insoluble synthetic polymers.
Types of Resins:
- Cation (Acid) Exchangers: replace cations (e.g., Na+) with hydrogen ions from the resin.
- Anion (Base) Exchangers: remove anions (e.g., Cl−) from the solution. Water purified in this manner is referred to as demineralized or deionized water.

Reverse Osmosis

A type of cross-flow membrane filtration
Water flows from a more concentrated to a less concentrated solution
Removes nearly all viruses, bacteria, pyrogens, and organic molecules; 90-99% of ions.
Filtration levels: microfiltration (0.1-2 µm), ultrafiltration (0.01-0.1 µm), nanofiltration (0.001-0.01 µm), reverse osmosis (<0.001 µm)

Non-Aqueous Solvents

Used in intramuscular injections for depot therapy. Factors affecting choice: toxicity, irritancy, flammability, cost, stability, and compatibility with other excipients.
Alcohol, USP (Ethyl Alcohol, Ethanol): Primary solvent for many organic compounds. Used as an antimicrobial preservative (with other agents like parabens, benzoates, and sorbates); frequently used with other solvents like glycols and glycerin to reduce alcohol amount. FDA recommends limiting alcohol content in OTC oral products (0.5% for children under 6, 5% for children aged 6-12, 10% for those over 12 and adults)
Rubbing Alcohol: Contains about 70% ethyl alcohol; volatile and flammable; rubefacient, germicide, skin cleanser; used for topical preparations.
Isopropyl Rubbing Alcohol: 70% by volume isopropyl alcohol; rubefacient, skin cleanser for preparation of needles and syringes.
Glycerin, USP (Glycerol): Clear syrupy liquid with sweet taste; miscible with water and alcohol; preservative qualities, often used as a stabilizer in internal preparations, and high concentrations in external preparations like phenol ear drops.
Propylene Glycol, USP: Viscous liquid; miscible with water and alcohol; frequently substituted for glycerin.
Fixed oils of vegetable origin: Nonvolatile oils (e.g., almond, olive, sesame, maize) suitable for parenteral use, some suitable for oral use as solvents for vitamins (A) and (D); fractionated coconut oil used for phenoxymethyl penicillin, which would hydrolyze rapidly in an aqueous solution; oils are frequently presented as emulsions.
Dimethyl sulphoxide (DMSO): Highly polar compound thought to aid drug penetration through the skin.
Ethyl ether: Used in extraction of crude drugs; often used as a cosolvent.

Formulation Additives in Solutions

Buffers: Resist pH changes when acid or alkali is added; compatible with other excipients; low toxicity; examples: carbonates, citrates, gluconates, lactates, phosphates, and tartrates (borates can be used for external application but not for mucous membranes or abraded skin)
Flavors and Perfumes: Enhance patient compliance; natural (fruit juices, aromatic oils) or synthetic (cheaper, more stable); available as extracts, alcoholic/aqueous solutions, syrups, or powders.

Oral Solutions

Antioxidant: Prevents oxidation of substances (most common: ascorbic acid).
Isotonicity Modifiers: Solutions made iso-osmotic with tissue fluid to avoid pain and irritation.
Preservatives: Prevent microbial contamination and maintain product stability. Types: water-soluble (benzyl alcohol, benzalkonium chloride) and water-insoluble (parabens, phenoxyethanol)

Preparation of solutions

Most pharmaceutical solutions are unsaturated
Strengths are usually expressed in percentages

Methods for Preparation of Solutions

Methods: prepared by simple solution, chemical reaction, sterilization, and extraction; techniques to hasten dissolution: applying heat, reducing particle size, and using solubilizing agents, vigorous agitation

Oral Solutions and Their Systemic Effects

Oral solutions, syrups, elixirs, spirits, and tinctures are prepared for specific effects.
Formulating a pharmaceutical solution must consider: solubility and stability of each solute, potential chemical/physical interactions, and solubility of components in solvents (stated in USP-NF).

Dry Mixtures for Solution

Many medicinal agents (particularly antibiotics) have poor stability in aqueous solutions.
Usually, the components (except solvent) are prepared as a stable dry mixture; the solvent is added as needed

Oral Rehydration Solutions (ORS)

Designed for rapid fluid loss and electrolyte replacement to avoid serious dehydration; should not be mixed with other electrolyte-containing liquids

Magnesium Citrate Oral Solution

Effervescent liquid with sweet, acidulous taste and lemon flavor; prepared by chemical reaction of magnesium carbonate with citric acid; contains magnesium citrate; used as a saline cathartic to relieve occasional constipation.