Liquid Dosage Forms - Solutions Flashcards
What is a solute
Dissolved agent in a solution
What is a solvent
Component in which the solute is dissolved
What is dissolution
The process of a solid going into solution
What is a solution
Thermodynamically stable, homogeneous system made of 2 or more components
What is a pharmaceutical solution
Liquid preparations that contain 1 or more substances dissolved in a suitable solvent or mixture of mutually miscible solvents
What is a saturated solution
Contains the max amount of solute that the solvent will accommodate at room temp. and pressure
What is a supersaturated solution
Contains a larger amount of solute than the solvent can normally accommodate at that temp. and pressure
What is drug solubility
Quantity of a drug maintained in solution at a given temp. and pressure expressed as the mL of solvent required to dissolve 1g of the drug
Dissolution process involves:
- Breaking of solute bonds
- Separation to provide space in the solvent for the solute
- Interaction between solvent and solute molecule/ion
What are the factors affecting dissolution
- pH
- Temperature
- Pressure
- Particle size
- Agitation
- Physical and chemical attributes of the solvent and the solute
Considerations for solute-solvent interactions
- Acceptability of solvent
- Compatibility of 2 or more solutes
- Chemical stability of solute in solution
- Effects of physical conditions
- Are additives required
Solvents criteria
- Completely dissolve the drug and other solid ingredients at the desired concentration -> homogeneous
- Non toxic and safe for injection or topical application
- Be aesthetically acceptable to the patient in terms of appearance, aroma, texture, and/or taste
Types of solvent
- Water - drinking water, purified water, water for injection
- Alcohol, USP: Ethyl alcohol, ethanol - miscible with water, used as a solvent and excipient in the formulation of oral pharmaceutical products, able to dissolve many water insoluble ingredients and used as antimicrobial preservative
- Dilute alcohol, NF - mixture of equal volumes of alcohol, USP and purified water, USP
- Rubbing alcohol - 70% ethyl alcohol by volume in water, denaturants, colorants, perfume oils and stabilizers.
- Glycerin, USP - clear syrupy, viscous liquid with sweet taste, miscible with both water and alcohol, used as preservative and stabilizer
- Isopropyl rubbing alcohol - contains 70% by volume of isopropyl alcohol
- Propylene glycol, USP - viscous liquid miscible with both water and alcohol
How to obtain purified water from drinking water
- Filtration
- Passing through activated carbon beds
- Addition of chemical additives/water softeners
- Deionisation and electrodialysis - remove cations and anions
- Reverse osmosis, ultrafiltration and distillation
Classify solutions based on
- Solute molecular size - micromolecular (MW<10,000)/macromolecular(MW>10,000)
- Solution’s use - oral, ophthalmic, otic, topical
- Composition/use - aqueous solutions (syrups: solutions contain sweeteners, aromatic water: solutions of volatile oils, mucilages: solutions of vegetable oils in water, aqueous acids), nonaqueous solutions (elixir, tinctures, spirits, liniments, collodion)
Considerations for solutions
- Unsaturated -> avoid precipitation due to changes in temp
- Strength
- Solutes differ in their solubilities: To increase dissolution -> use heat, decrease particle size, enhancers, agitation, etc.
- Oral adult solutions may need to be diluted to a pediatric form
- Some medicinal agents (e.g. antibiotics) have insufficient stability in aqueous solution and are marketed as dry mixtures for solutions
Applications for solutions
- Vehicles for oral, parenteral, topical, otic, ophthalmic, and nasal products
- Flavorings, buffers, preservatives, and suspending agents for a variety of liquid dosage forms
- Components of extemporaneously prepared products
- Test solutions used in analysis of pharmaceutical products of all types
- Dry mixtures for solutions need to be mixed with water for oral administrations
Definition of syrup
A concentrated or nearly saturated solution of sucrose or sucrose substitute in water
Types of syrup
- Simple syrup: contain only sucrose and purified water
- Nonmedicated/flavoring syrups: contain pleasantly flavored substances and employed as a pleasant tasting vehicle for therapeutic agents
- Medicinal syrups - contain therapeutic compounds
Components of syrup
- purified water
- medicinal agents
- sugar: sucrose or sugar substitute to provide viscosity, sweetness, mask the taste and prevent drug irritation
- antimicrobial preservatives: benzoic acid, sodium benzoate, Methylparaben, propylparaben
- flavorants: volatile oils, vanillin
- colorants: green-mint, brown-chocolate
- others: special solvents, solubilizers, stabilizers and thickeners
=> compatibility is impt - no interaction/reaction between the ingredients
Preparation of syrup
- Solution with heat: Problem: inversion of sugar due to hydrolysis
- Solution with agitation but without heat: use of mixers and agitators
- Addition of sucrose to a medicated liquid or to a flavoured liquid
- Percolation: filtration of a liquid for extraction
Sources of sweeteners
- Sugars: sucrose
- Non-sugar polyols: sorbitol, glycerin, propylene glycol, mannitol - polyols can provide viscosity and may act as cosolvents and preservatives
- Non-nutritive artificial sweeteners: aspartame, saccharin -> do not impart viscosity
Definition of elixirs
Clear, sweetened hydroalcoholic solutions intended for oral use and are usually flavored to enhance their palatability; can be medicated/non-medicated
Alcoholic content of elixirs
5-40%
Preparation of elixirs
- Simple solution with agitation and/or by admixture of 2 or more liquid ingredients
- Alcohol soluble and water soluble components are dissolved separately in alcohol and purified water respectively -> 2 mixtures
- Aqueous solution added to the alcoholic solution -> mixture made to the specific volume by the given solvent
- alcohol added to keep all contents in solution
- addition of aqueous solutions may cause turbidity/separation by lessening alcohol concentration
Elixirs compared to syrups
- Less sweet and viscous
- Less effective in masking the taste of medicinal agents
- Dissolve both water soluble and alcohol soluble materials
- More stable and easier to prepare
- Preferred
Definition of spirits
Alcoholic/hydroalcoholic solutions of volatile substances (volatile oils) and prepared by simple solution, solution by maceration/distillation
Alcoholic content of spirits
60%
Spirits used as
flavoring or therapeutic agents
Definition of tinctures
Alcoholic/hydroalcoholic solutions prepared from vegetable/chemical substances generally extracted by maceration/percolation
- must be closed tightly in light resistant containers
Alcoholic content of tinctures
15-80%
Definition of collodions
Liquid preparations containing nitrocellulose pyroxylin in a solvent mixture of alcohol and ethyl ether
Uses of collodions
provide topical protectives or as a topical drug vehicle
Definition of liniments
Alcoholic/oleaginous solutions or emulsions of various substances intended for external application to skin, generally with rubbing
Examples of tinctures
vanilla tincture USP, iodine tincture USP
