What are Pharmaceutical solutions?
A liquid preparation that contain one or more chemical substances dissolved in a suitable solvent or mixture of mutually miscible solvents.
(USP definition)
What are syrups?
Solutions containing high concentration of sucrose or other sugars
What are elixirs?
A clear, pleasantly flavored, sweetened hydro-alcoholic liquid containing API for oral use.
What are spirits?
An alcholic or hydro-alcoholic solution of volatile substance.
What are Tinctures?
An alcoholic or hydro-alcoholic solution from plants or chemcials
What are some extracts?
A concentrated preparation of natural products by extraction
There are also some lotions, sprays, medicated oils and others.
These are about of pharmaceutical solutions
How are pharmaceutical solutions classified?
Route of administration
- Oral, topical, otic, ophthalmic, parenteral and others
How do you describe solubility quantitatively and qualitatively?
Quantitative is by the concentration of drug (API)
Qualitative is in terms of approximate solubility
Define Solubility
Solubility is defined in quantitative terms as the concentration of a solute in a saturated solution, at a certain temperature and pressure.
S (solubility) indicates the saturated solution concentration (mol/L)
What is a saturated solution?
A saturated solution of a solid material is in equilibrium between the solute phase and the solid phase.
What is a supersaturated solution?
A supersaturated solution is possible; some substances are dissolved in a higher concentration than it could normally obtain at equilibrium.
What are the solubility definitions as well as the ranges?
- Very Soluble (VS)
- Freely Soluble (FS)
- Soluble
- Sparingly soluble (SPS)
- Slightly soluble (SS)
- Very slightly soluble (VSS)
- Practically insoluble (PI)
What are the three steps a substance must undergo to dissolve?
Give the Equation that is involved.
- Solvent and solute are segregated, each interacts primarily with other molecules of the same type.
- To move a solute molecule into solution, the interactions among solute molecules in the crystal (lattice energy) and among solvent moelcules in the space required to accommodate the solute (cavitation energy) must be broken.
- Once the oslute molecule is surrounded by solvent, new stabilizing interactions between the solute and solvent are formed (solvation energy).
S + S = e ^ (- delta G release - delta G cavity + delta G solvation) / RT
What are the different intermolecular forces?
- Hydrogen Bond
- Ionic interactions
- Van der Waals
What are the mechanisms involved in Polar Solvents?
- Polarity of a molecule (molecular dipole moment, ration of polar and nonpolar groups)
- Hydrogen-bond formation: Strong
- Ionization of water
What is involved in semi-polar solvents?
- They are often used as _intermediate solvent_s (aka co-solvents)
- Can induce some degree of polarity in nonpolar molecule
- e.g. acetone, glycerin, propylene glycol used as co-solvents to increase the solubility of organic molecules.
The functional groups that surround semi-polar solvents are Alcohol, aldehyde, ketone, and amine.
What is a Dipole?
A separation of two opposing charges q over a distance r
What is a dipole moment?
u = qr
(a measure of molecular polarity)
q = charge difference between polar and non-polar
r = relates to the shape
Desribe Dielectric Constant
Capacitance: C=q/V
Dielectric constant: Cx/Co
The bigger the dielectric constant the more polar it is.
(Increase Dielectric Constant, Increase Polarity)
When you have a mixture of liquid and liquid what is the miscibility between two liquids described as?
- Complete miscible: refers to a liquid solute that will form a solution with a liquid solvent over any concentration range. e.g. water-alcohol, glycerin-alcohol, benzene-tetrachloride
- Partial Miscibility: when liquids are not completely miscible, their solubility (miscibility) needs to be disscuess. e.g. binary system of phenol and water
Phase diagrams are a two component system (binary)
What are phase diagrams and give an example as well as a critical solution temperature.
Understand the diagram
- Phase diagrams are used to show the equilibrium conditions between multiple phases
- Example: A temperature-composition diagram to describe the influence of temperatrue miscibility at different compositions.
- The critical solution temperature 66.8 degress Celcius on the right.
What are involved in phase diagrams of three-component systems?
Ternary System
Triangular corrdinate graphs is useed to describe the equilibrium conditions between 3 phases.
What are the type of things that influence the solubility of a solid?
- Influence of pH: calculating the solubility of weak electrolytes
- Influence of solvents
- Influence of surfactants
- Influence of complexation
- Influence of other factors
