Elixirs and Their Preparation

Elixirs

• Aromatic elixirs are flavored, alcoholic solutions containing 21%-23% alcohol.
• Compound benzaldehyde elixirs are flavored, alcoholic solutions containing 3%-5% alcohol.
• Elixirs are self-preserving if they contain over 12% alcohol.
• Elixirs can cause precipitation of ingredients if water is added due to a decrease in alcohol concentration.
• Medications extracted from tinctures and fluid extracts can separate from elixirs due to a decrease in alcohol concentration.

Elixir Preparation

• Water-soluble substances are dissolved in a portion of water.
• Sucrose is added to increase viscosity and decrease water's dissolving power, but only after the primary solution is prepared.
• Alcohol-soluble ingredients are dissolved in alcohol.
• The aqueous solution is added to the alcoholic solution.
• The solution is filtered, and the volume is adjusted to the desired amount.
• Elixirs must be clear and can be filtered after standing for a few hours, or clarified with talc to absorb excess oils.

###Types of Elixirs

• Non-medicated (Aromatic) elixirs: Used as a pleasant-tasting vehicle.
• Medicated elixirs: A therapeutic agent is added to an existing medicated elixir, or a medicated elixir is diluted.
• Examples:
  • Antihistamine Elixir: For relief of allergies.
  • Phenobarbital Elixir: Contains 14% alcohol to keep phenobarbital in solution.

Collodions

• Are liquid preparations containing pyroxylin (nitrocellulose derivative) in a mixture of ethyl ether and ethanol.
• Applied to the skin using a brush or applicator, leaving a film of pyroxylin after the ether and ethanol evaporate.
• Salicylic Acid Collodion USP: Contains 10% w/v Salicylic Acid in Flexible Collodion USP, and is used as a keratolytic agent for corns and warts.
• Flexible Collodion: Made by adding castor oil and camphor to collodion, making it more pliable.

Glycerites

• Solutions or mixtures of medicinal substances, primarily plant matter, in at least 50% by weight glycerin.
• Benzocaine Otic Solution USP: Prepared using glycerin as the sole solvent.
• Otic Solutions: Glycerin is used to help remove earwax (cerumen).
• Glycerins are hygroscopic and should be stored in tightly closed containers to prevent moisture absorption.

Liniments

• Solutions or mixtures of various substances in oil, alcoholic solutions of soaps, or emulsions.
• Intended for external application and should be labeled as such.
• Applied by rubbing to the affected area.
• Oil-based liniments are used for their soothing properties, while alcoholic liniments provide rubefaciant (redness) and counterirritant effects.
• Liniments penetrate the skin more readily than oil-based liniments alone.

Oleovitamins

• Concentrated vitamins A and D in fish liver oil or edible vegetable oil.
• Vitamins are unstable in the presence of rancid oil and should be stored in:
  • Small, tight containers.
  • Protected from light.
  • Under vacuum or inert gas.

Galenical Extraction

• The process of separating soluble constituents of crude drugs from insoluble materials (albumin, cellulose, gum, pectin, starch, sugars) using a suitable solvent (menstruum).
• Crude drug: The raw plant material.
• Extractive: The soluble constituents extracted from the drug.
• Marc: The insoluble residue remaining after extraction.
• The solvent should extract the maximum amount of active substances and the minimum amount of inert substances to ensure quality and stability.
• Inert substance effects:
  • Oxidation: Can cause darkening of the extractive over time.
  • Hydrolysis: Can convert inert substances into insoluble compounds that precipitate out.

Selection of Menstruum (Solvent)

• Water:
  • Extracts a considerable amount of substances prone to hydrolysis or oxidation.
  • Extracts mucilaginous and carbohydrate materials, leading to viscous solutions that are difficult to process and susceptible to microbial growth.
• Alcohol:
  • Good solvent for alkaloids, glycosides, and resins. Does not dissolve inert gums, sugars, and albumin.
  • Inhibits enzymatic action and microbial growth (preservative).
  • Not used alone as a menstrum because it's expensive.
• Hydro-alcoholic solvent:
  • Combines the advantages of alcohol and water while minimizing their disadvantages.
  • Good solvent for many plant substances.
• Glycerin:
  • A good cosolvent with water/alcohol; it extracts and prevents precipitation of inert materials upon standing.
  • Has a preservative action, contributing to the stability of the product.

Methods of Extraction

• Maceration:
  • Properly comminuted drug is soaked in the menstruum for 2-14 days to soften cellular structures and allow soluble constituents to dissolve.
  • The marc is washed to remove any remaining extractive by repeatedly passing more menstruum through the strainer or filter.
  • Most efficient method for drugs with little or no cellular material (e.g., benzoin, aloe, tolu).
• Percolation:
  • Comminuted drug is extracted by the slow passage of a suitable solvent through a packed column of the drug.
  • The extracted solution is known as the percolate.
  • The flow of menstruum through the column is typically downward, driven by gravity and the weight of the liquid column.
  • More sophisticated apparatus may use positive air pressure at the inlet and suction at the outlet to regulate flow.

Fluid Extracts

• Liquid preparations of vegetable drugs prepared by percolation.
• Contain alcohol as a solvent or preservative, or both.
• Each ml contains the therapeutic constituents of 1 g of the standard drug.
• Too potent for self-administration, so used as a component in other liquid dosage forms (e.g., syrups).
• Often modified with flavoring or sweetening agents to improve taste.

Extracts

• Concentrated preparations of vegetable or animal drugs.
• Active constituents are extracted using suitable menstrua by percolation.
• Solvent is either evaporated completely or nearly completely to a desired concentration.
• Can be categorized as:
  • Semi-liquids: Liquids with syrup consistency.
  • Plastic (pilular) masses: Used in ointment or suppository preparation.
  • Dry powders: Used for capsules, powders, or tablets.

Galenical Resins

• Prepared by percolating a crude drug with an alcoholic solvent.
• The resinous constituents are precipitated by pouring the percolate into water.
• Contain alcohol-soluble, water-insoluble constituents of the crude drug.

Oleoresins

• Liquid galenical extractives of natural oils and resins, extracted by percolation using acetone or ether as a solvent.