Galenical Dosage Forms: Prep and Processes

• Galenical dosage forms refer to pharmaceutical preparations from natural sources like plants and animals
• Galenicals are named after Claudius Galen, whose theories formed the basis of European medicine
• Natural products have been used as remedies for ailments
• Isolating active ingredients can be beneficial but may be expensive and lead to loss of activity
• Galenical preparations remain relevant due to the limitations of isolating active ingredients

Processes for Galenical Preparation

• Maceration involves steeping plant material in a solvent
• Digestion uses heat to enhance extraction
• Infusion involves soaking material in a liquid
• Decoction involves boiling the material in a solvent
• Percolation involves continuously flowing solvent through plant material
• Reserved percolation is where the first fraction is set aside
• Expression is squeezing out liquid from drug materials

Maceration

• It is used for preparing infusions, tinctures, and extracts
• Plant material is chopped and placed in a vessel
• Menstruum is added and the vessel is agitated occasionally for about 7 days
• After 7 days, the liquid is strained out
• The remaining marc is pressed, and the liquid is added to the strained liquid
• The marc can be macerated a second time, and the liquids combined, which is called repeat maceration

Digestion, Infusion, and Decoction

• Digestion is maceration with heat
• Digestion is beneficial when the solvent has low power
• Not suitable for volatile components
• Infusion involves soaking the material in cold or hot menstruum for a short time
• Decoction involves boiling the solvent during extraction

Limitations of Digestion, Infusion, and Decoction

• These processes may degrade thermolabile components
• Digestion requires a constant energy supply to keep the solvent hot
• Volatile components may be lost

Limitations of Maceration

• Maceration takes time - up to 7 days or more
• The extracting solvent reaches saturation, making full extraction difficult
• Water as a solvent may allow fungal growth during maceration

Percolation

• Percolation is an extraction technique of continuously flowing solvent to help extract soluble active components efficiently
• Percolation uses a percolator, a cone-shaped vessel, through maceration, pressing and filtration
• A percolator is a short successive maceration where a solvent is passed through the material in a conical vessel (percolator)
• The solvent slowly passes to extract soluble components

Percolation Procedure

• Moisten the material with percolation solvent and keep in a vessel for approximately 4 hours before packing the percolator
• This pre-treatment hydrates the cells for effective extraction and to reduce occlusions from cell-swelling
• Pack pre-treated material into the percolator, cover with filter paper, and stabilize with sand grains
• Introduce solvent to percolate through the packed material
• To macerate, when the solvent drips, close the tap for 24 hours
• Open the tap, and regulate flow of menstruum through material
• Continuously feed the percolator with solvent to prevent drying and caking
• Collect 3/4 of the final product volume via the percolate discharge tube before pressing the rest of the marc
• Additional additives can be added, then adjust the volume with extracting solvent

Reserved Percolation Method

• The first fraction is collected after pre-percolation maceration and is reserved
• Percolation continues until the plant material is exhausted
• A soft mass is obtained via solvent evaporation
• The soft mass is dispersed in the reserved percolate; adjust the volume
• Useful in situations when a concentrated product is needed

Percolation Limitations

• It is not suited for gummy materials and animal tissues which can occlude the perforated plate
• Exhaustive percolation needs a high solvent volume

Expression

• Process to squeeze out liquid from drug materials
• Useful to harvest oil from seeds and fruits via pressure
• Can press marc from percolation and maceration

Expression Qualities

• Generates low heat, so you can process thermolabile compounds

Expression Limitations

• Useful only on soft compressible materials
• Full extraction may not be achieved

Galenical Dosage Forms

• Liquid dosage forms: Infusions and Tinctures
• Solid dosage forms: Extracts and Resins
• Oleaginous dosage form: Oleoresins and Infused oils

Infusions

• Liquid preparations of vegetable origin are prepared through maceration, percolation, and infusion administered orally

Infusion Types

• Fresh Infusions: Prepared via short maceration with cold or boiling water
• Concentrated infusions: Made when using weak alcohol extraction
• Dilute infusions: Made from concentrated infusions using dilution. They may also be created with water as the extrating solvent.

Extract

• Galenical preparations with a higher proportion of a drug's active principle(s) than a corresponding infusion or tincture
• The active compound is extracted using a solvent like water or alcohol via maceration.
• The liquid after filtration is concentrated by evaporation.

Extract Classifications

• Aqueous Extracts: Prepared using water or chloroform water
• Alcoholic Extracts: Prepared using alcohol
• Ethereal Extracts: Prepared using ether

Extract Consistencies

• Liquid extracts
• Soft extracts which may be standardized or non-standardized
• Dry extracts

Tinctures

• Alcoholic solutions of vegetable drugs prepared by maceration, percolation, or simple admixture
• Alcohol preserves tinctures
• Common alcohol concentrations in tinctures: 45, 60, 70, and 90%v/v
• Higher concentrations are used to extract alkaloids, resins, and volatile oils
• Dilute concentrations are used to extract gum, albuminous matter, and sugars

Tincture Classifications

• Tinctures with admixture: Made by diluting galenical preparations with alcohol
• Tinctures with maceration: Prepared using alcohol as the menstruum
• Tinctures with modified percolation: Prepared by percolating material with alcohol

Standardisation of Galenicals

• Ensures uniform potency and limits batch variability

Standardisation Method Types

• Chemical
• Biological
• Arbitrary

Chemical Standardisation

• Titration
• Spectrophotometry
• HPLC
• Mass Spectroscopy

Biological Standardisation

• Measurement of biological effects, such as heart rate, blood pressure, etc

Arbitrary Standardisation

• Depends on organoleptic characters such as flavor, color intensity, and taste