liquids Flashcards
several reasons why liquids are used internally instead of other dosage forms (5)
Easier to swallow Only suitable dosage form Irritation Flexibility Immediate drug availability
Classification of liquids (2)
by types of system
by routes of administration
types of classification by system and example
Homogeneous – examples are solutions
Heterogeneous – examples are emulsions and suspensions
examples of classification by route of administration
oral solution
parenteral solution
opthalmic solution or suspensions
Topical solution or suspensions
Liquid preparation that contain one or more chemical substances dissolved in a suitable solvent or mixture of mutually miscible solvents.
pharmaceutical
pharmaceuticals are classified by ____ or ___. Examples are:
composition or use
syrup, elixir, spirits, aromatic waters, tinctures or fluid extracts
Aqueous solutions containing sugar
syrup
Sweetened hydroalcoholic (combinations of water and ethanol) solutions
Elixir
Alcoholic solutions of aromatic materials
Spirits
Aqueous solutions of aromatic materials
Aromatic waters
Solutions of prepared by extracting active constituents from crude drugs
Tinctures or Fluid extracts
pharmaceutical solutions can be aqueous or non-aqueous and do not necessary need to be in the ____ state
liquid
What are some Disadvantages of Solutions
- Relative chemical stability (vs. solids)
- Medium for microbial growth
- Bulky
- More pronounced distaste
- Potential dosing errors
the substance being dissolved
Solute
medium or vehicle in which solute is dispersed or dissolved
Solvent
important issue to address when considering ease of production is
dissolution
important issue to address when considering dosage uniformity is
there isn’t any important consideration
important issue to address when considering stability is
chemical pH, temperature, antioxidants
microbial preservation
important issue to address when considering patient acceptance is
palatability, appearance
important issue to address when considering drug release is
there isn’t any important consideration
process of dissolution (drug being dissolved in solvent) requires 3 main steps
Work is required to separate particles of solute in the crystal
Work is required to separate molecules of solvent
Energy is necessary with interaction
The Dissolution process involves:
Dipole-dipole interactions
Hydrogen bonding
Polarity
Three of polarity are:
Polar (water)
Semi-polar- (ketones, alcohol)
Non-polar (carbon tetrachloride, benzene, mineral oil)
Weak interactions, loose association orientation of positive and negative poles
Dipole-dipole interactions
Strong interaction between hydrogen atom and electronegative atom (F, O, N)
Examples are water, alcohol molecules, carboxylic acid, polypeptides
Hydrogen bonding
Solubility of drug due in large part to polarity of solvent
polarity
contains:
High dielectric constant
Break covalent bonds by acid-base reactions
Dipole interaction forces (hydrogen bonding)
Polar (water)
Induces polarity in nonpolar solvents
Semi-polar- (ketones, alcohol)
Used to increase aqueous solubility of weak electrolytes and non-polar molecules
Solute more soluble in mixture of solvents (alcohol/water mixture)
Co-solvents
Examples of co-solvents are
Glycerin
Alcohol
PEG
Propylene glycol
contain:
Low dielectric constant
Cannot reduce attraction, break covalent bonds or ionize weak electrolytes
Non-polar (carbon tetrachloride, benzene, mineral oil)
Measure of polarizability of a molecule -> “like dissolves like”
Dielectric constant
The reduction of particle size increases the total ____ ____ of the solid in contact with the solvent, and dissolution occurs more rapidly.
surface area
The rate of dissolution depends on many factors:
a. free surface energy and the shape of the particles
b. temperature
c. type of agitation
d. amount of material already in solution
e. viscosity and volume of the solvent
f. concentration of the dissolved solute
The exposure of new surfaces and the condition of the surface modifies the rate; if gas pockets or an insoluble coat form on the surface, the rate of dissolution will be _______.
decreased
sink conditions in Noyes and Whitney
if Ct (concentration at that instant) «_space;Cs (conc of saturated sln), then may omit Ct
_____ have different crystal forms and therefore have different energy contents.
So solubilities differ
Isomers
Fumaric acid forms a more stable crystal so is less ____ than Maleic acid
soluble
Many organic medicinal compounds are capable of existing in two or more crystalline
forms with different arrangements of the molecules in the crystal lattice and these are
referred to as ______
polymorphs
The X-ray diffraction patterns, densities, melting points, solubilities, crystal shape and electrical properties vary
with the ______ form. However, in the ___ or ____ state no difference is
discernible.
polymorphic
liquid
vapor
The _____ polymorph possesses a higher solubility and dissolution rate than does the
stable form, and this phenomenon may be used to advantage in biopharmaceutics
metastable