PRX 340 pharmaceutical solution lecture

solutions

chemically and physically homogeneous mixture of 2 or more substances to form a thermodynamically stable dispersion

solubility

spontaneous interaction of 2 or more substances to form a homogeneous molecular dispersion

solute

the solid or liquid that is dissolved in another liquid

solvent

liquid containing the solute

vehicle

pharmaceutical solvent or solution used to dispense or carry the drug

pharmaceutical solutions

liquid preparations that may or may not have 1 or more soluble drug substances usually dissolved in a suitable solvent or mixture

syrup

clear solution where there’s no solid floating in the system

diagonal suspension

tiny particles that are dispersed in a liquid

preservative

prevents microbial growth in the system

chelator

compound that binds to divalent metal ions and take out of solution

co solvent

increase solubility

saturated solution

the solute is in equilibrium with solid phase

unsaturated solution

contains less dissolved solute in a concentration that is needed for complete saturation at a given temperature

supersaturated solution

Contains more dissolved solute than normally permitted at that temperature

trigger in precipitation

small particle that can cause precipitation bc it acts as a nucleus

molarity

used for acids, bases, electrolytes

molality

used in osmotic and tonicity calculations

mole fraction

used in thermodynamics

%w/v

used for pharmaceutical solutions

purpose of descriptive terms

to give an idea about the solubility behavior of a drug

what will be the orientation of water around chloride ion?

Water molecules orient themselves around a chloride ion with their hydrogen atoms pointing directly toward the chloride ion and their oxygen atom facing outward

what are the properties of water?

contains all known intermolecular forces of attraction, highly ordered, high polarity, high dielectric constant

what properties do inter molecular forces have in water

van der waal’s forces, hydrogen bonds, dipole interactions, induced dipole interactions

what properties do semi polar solvents have in water

van der waal’s forces, dipole interactions, induced dipole interactions

what properties do non polar solvents have in water

van der waal’s forces and induced dipole interactions

dielectric constant

effectiveness of a medium to keep charged particles apart relative to vacuum

hard water

unsuitable for pharmaceutical purposes, contains bicarbonates and sulfates of Ca and Mg

soft water/deionized water

obtained from removing above salts with ion exchange resins, not suitable for pharmaceutical purposes

purified water

deionized water that meets EPA standards, may be used for non sterile purposes

distilled water

distilling hard or soft water. some volatile organic matter and salts may be present

buffers

solutions that resist changes in pH

syrups

aqueous pharmaceutical solutions containing sugars

elixirs

hydro-alcoholic pharmaceutical solutions containing a sweetner

spirits

pharmaceutical solutions of volatile aromatic materials where the solvent is alcohol, also used as flavoring agents

aromatic waters

solutions of volatile aromatic materials where the solvent is water

tinctures and fluid extracts

alcoholic and hydro-alcoholic pharmaceutical solutions prepared by extracting active constituents from crude drug material, they differ in their concentration

miscellaneous solutions

mouth washes, nasal, ophthalmic, otic and parenteral solutions, astringents, antibacterial topical solutions

sterile

absence of living microorganisms

pyrogen free

pyrogens are fever producing organic substances arising from microbial contamination

intravenous injections

injected directly into the blood circulation

intramuscular injections

injected in muscle mass, mid deltoid area and gluteus medius

subcutaneous injections

injected in the subcutaneous tissue, beneath the skin layers like the arm or thighs

intra dermal injections

injected in the most superficial skin layer

bolus

single, small volume injection

infusion

slow, large volume injection

sterile water

microbes destroyed, but toxins may be present. not suitable for inejctions, but may be used for other purposes like ophthalmic preparations

pyrogen free sterile water

may be used for large volume parenterals, pyrogens removed by filtration or repeated distillation, should not have more than 0.25 USP units of pyrogen, should not have preservatives

bacteriostatic water for injection

may be used for small volume parenterals, should not have more than 0.5 USP units for pyrogen, contains preservatives to control microbial growth

function of isotonic agents

Adjust tonicity

function of buffering components

to maintain pH of the solution

function of antimicrobial preservatives

Control microbial growth

function of antioxidants

reduce oxidation

Why can a solution be colored but still optically clear?

A solution can be colored because dissolved substances absorb certain wavelengths of light. It remains optically clear because its components are dispersed at the molecular level and do not significantly scatter visible light.

Why does temperature affect saturation?

Temperature affects how much solute can dissolve in a solvent. For many solids, increasing temperature increases solubility, allowing more solute to dissolve before reaching saturation.

Why may poor solubility reduce oral bioavailability?

A drug must dissolve in gastrointestinal fluids before it can be absorbed. Poor solubility can limit dissolution and reduce the amount of drug available for absorption.

Why does water dissolve ionic compounds?

Water is a polar solvent with a high dielectric constant, allowing it to separate positive and negative ions. Water molecules surround and stabilize these ions through hydration.

Why do longer hydrocarbon chains reduce water solubility?

Longer hydrocarbon chains increase the non-polar portion of a molecule. This makes the molecule less compatible with polar water, reducing its solubility.

Why do polar and non-polar solvents dissolve different substances?

Polar solvents dissolve polar and ionic substances through dipole interactions, hydrogen bonding, or ion solvation. Non-polar solvents dissolve non-polar substances mainly through dispersion forces.

Why do alcohol and water exhibit volume contraction?

Alcohol and water form hydrogen bonds that allow their molecules to pack more closely together. As a result, the final volume is smaller than the sum of their individual volumes.

Why can cosolvents improve drug solubility?

Cosolvents change the properties of a solvent mixture, including its polarity and dielectric constant. This can make the mixture more suitable for dissolving poorly water-soluble drugs.

How do buffers respond to added acid or base?

When acid is added, the conjugate base reacts with the added hydrogen ions. When base is added, the weak acid reacts with hydroxide ions, minimizing changes in pH.

Why does increasing the conjugate-base-to-acid ratio raise buffer pH?

According to the Henderson–Hasselbalch equation, increasing the conjugate-base-to-acid ratio increases the logarithmic term. Therefore, the buffer's pH increases.

Why are some medications supplied as dry mixtures?

Some drugs are unstable in aqueous solutions and may degrade during storage. Keeping them dry improves stability and extends shelf life until reconstitution.

Why do injectable formulations require special purity controls?

Injectable formulations bypass many of the body's natural protective barriers and enter tissues or the bloodstream. Therefore, they must meet strict requirements for sterility, pyrogens, and other contaminants.

Why are some injections suspensions rather than solutions?

Some drugs have low solubility and cannot dissolve sufficiently in the vehicle. Suspensions can also provide prolonged drug action by allowing the drug to dissolve slowly after injection.

Why may heat-sensitive solutions be sterilized by filtration?

Heat-sensitive drugs may degrade when exposed to high temperatures. Filtration removes microorganisms without exposing the drug to damaging heat.

Why are sterilization and pyrogen removal different?

Sterilization destroys or removes microorganisms, while pyrogen removal eliminates fever-producing substances such as bacterial endotoxins. A solution can be sterile but still contain pyrogens.