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Pharm 124 Solutions Exam With Complete Solution
what is the definition of a solution? - ANSWER a chemically and physically homogenousmixture of two or more substances
what are the 3 classifications of solutions? ex what are they based on? - ANSWER 1. based onthe nature of the particles (true solutions, colloidal soln, or dispersions)
- based on route of administration
- based on solvent/dispersion medium (aq or non aq) what are the advantages of solution dosage forms? - ANSWER provide completelyhomogeneous doses doses are easily adjusted immediately available for absorption and distribution can be use by any route of administration can easily be administered to patients unable to swallow caps or tabs (children's dosing) what are the disadvantages of solution dosage forms? - ANSWER chemicals have lowerstability in solution drugs may not be soluble in acceptable solvents solutions may provide suitable media for microorganism growth (requires additionalpreservatives) increased problems associated with handling. packaging, transporting, storage oral dosage forms may require additional additives/techniques to mask taste solutions are generally provided in multiple dose containers requiring measuring (lessaccurate)
what is dissolution? - ANSWER The transfer of molecules or ions from a solid state intosolution
dissolution rate doesn't = solubility high solubility is typically associated with high dissolution rate what are the 3 steps of dissolution? - ANSWER 1. Interfacial reaction: solid becomes moleculesof solute
- Moving into the liquid and replacement with solvent molecules
- diffusion through the boundary (stagnant layer) surrounding the particles Gibbs free energy equation - ANSWER ΔG = ΔH - TΔS gibbs free energy is negative for spontaneous processes delta S is usually positive for dissolution = entropy change Fick's Law - ANSWER migration of solute through stagnant layer is driven by concentrationdifferent between the surface of the solute and the bulk solution
(dC/dt)= kΔC = k(Cs-C) Noyes-Whitney equation - ANSWER describes dissolution of spherical particles (dm/dt) = [k1A(Cs-Ct)/h] dm/dt - rate of mass transfer of the solute
products (ie, a quality control tool)
- as a prognostic tool for the performance of solid drug products in the gastrointestinal tract what are the 4 dissolution apparatus' in US and europe? - ANSWER baket apparatus paddle apparatus reciprocating cylinder flow through cell is potable water used for dosage forms? - ANSWER no what dosage forms is purified water used for? - ANSWER oral and topical preparations NOTparenteral
water is used for injections - ANSWER USP; distillation or reverse osmosis not required to be sterile, but has to be pyrogen free used in manufacture of parenteral products that are sterilized after manufacturing Sterile Water for Injection, USP - ANSWER water for injection that has been subsequentlysterilized packaged in single dose containers with no preservatives, anti-microbial or other addedsubstances used for small and large volumes of parenterals bacteriostatic water for injections USP - ANSWER contains one or more suitable antimicrobialagents
used to prepare small volume parenteral (otherwise antimicrobial agents too high) not for use in newborns label must ensure chemical compatibility between bacteriostatic agent and medicinal ingredients Alcohol (BP or USP) - specifics ethyl alcohol - ANSWER alcohol and water = hydro alcoholicsolution (dissolves both alcohol and water soluble compounds) -used to prepare elixers alcohol is miscible with water, semi polar solvents as well as other organic solvents such aschloroform, ether, acetone
what are advantaged of alcohol as a solvent? - ANSWER higher solubility increases stability -decrease in hydrolysis -decrease in bacterial growth other alcohols (ethyl) include: denatures (contains additives to render unfit for internal use absolute (100%); dehydrated alcohol (99.5%), water free diluted alcohol NF: equal part alcohol/water isopropyl alcohol as solvent - ANSWER similar solvent properties to alcohol but contains lesswater (99% isopropanol) -comparable miscibility
- better antiseptic properties (>70%) than alcohol
ANSWER directly, pressure this is henrys law note*** solubility of most gases in liquids decrease as temp increases (principle for removingCO2 by boiling water)
what are the terms used to describe the solubility of two liquids? - ANSWER miscible - solublein all proportions (alcohol or glycerin in water) partially miscible - soluble in definite proportions (phenol and water) Immiscible - insoluble or nearly insoluble in any proportion (mineral oil and water) what are factors that affect solubility of solids in liquids? - ANSWER temp structure solvent and co colvent other solutes solubilizing agents complex formation pH how does temperature effect solubility of solid in liq - ANSWER temp increases solubility, andin turn increases dissolution rate
the dissolution process is usually endothermic ie heat is absorbed -therefore increase temp = increase solubility if ΔH is exothermic; increase in temp results in decrease solubility
how does structure effect solubility? - ANSWER is the drug compound polar or non polar?'
- aq solubility on non ionic and non polar can be improved by introduction of hydroxyl groups is the drug compound a week acid or base?
- conversion to its corresponding salt increases its solubility eg salicylic acid vs sodiumsalicylate 1 in 550 vs 1 in 1 water
- variations in pH can also be used to increase solubility does the drug have a different crystalline form?(polymorphism)
- can increase solubility through use of different polymorph what are examples of semi polar solvents? - ANSWER ethyl alcohol, isopropyl alcohol, gycols what does the partition coefficient describe?. - ANSWER the distribution of the solute betweentwo immiscible solids
to measure the drugs ability to partition into lipid membranes What is the partition coefficient equation? - ANSWER P = Co/Cw -> log P P = n-ontanol / water partition coefficient generally if
- log P > 0. then drug is lipid soluble
- log P < 0 drug is water soluble what can happen it log P is too high or low? - ANSWER it can result in poor absorption ie thereis an optimum range for different routes of administration
what is the common ion effect - ANSWER added electrolyte containing either A+ or B- will shiftthe equilibrium such that the equilibrium constant, Ksp = CA +CB remains constant ex. added B- will necessitate a decrease in [A+] which occurs through precipitation of AB; thisdecrease in the solubility as a result of the presence of B- is called the common ion effect
what is indifferent electrolytes? - ANSWER (no common ion) activity coefficient decrease with increasing concentration of ionic solute (ionic strength) what are solubilizing agents used for? and 2 examples - ANSWER increase the solubility of apoorly soluble drug
ex
- surfactants (surface active agents)
- complexing agents What are surfactants? - ANSWER consist of both polar and non polar groups (amphiphilic) form micelles in water complexing agents form __________ associations with drug molecules which __________ solubility- ANSWER non-covalent ; increases
what is stacking interactions? - ANSWER the complexing agent stacks with the nonpolar regionof a poorly soluble drug to exclude water contact lowers total energy of the system increasing solubility
what is inclusion complexes - ANSWER complexing agents possesses a cavity into which thedrug can insert again shielding it from water contact
- should have non polar core and polar exterior
- cyclodextrins are most common can hold hydrophobic drugs inside of complex ex febreeze what is the effect of pH on solubility? - ANSWER most drugs are weak acids or weak bases, pHstrongly influences solubility as a result of the acid-base equilibrium that exists
weak acid equation - ANSWER HA <-->(Ka) [(H+) + (A-)] acid dissociation constant equation - ANSWER Ka= [H+][A-]/[HA] weak base equation - ANSWER B + H+ <--> BH+ acid dissociation constant equation for weak base - ANSWER Ka = [H+][B]/[BH+] recall B + H2O <--> BH+ + OH- and Kb = [BH+][OH-]/[B] Henderson-Hasselbalch equation - ANSWER pKa = pH + log [HA]/[A-] and pKa = pH + log[BH+]/[B]
pKa = pH + log cu/ci nd pKa = pH + log ci/cu cu = concentration of unionized species ci = concentration of ionized species
pH = pKa + log [salt]/[acid] for weak acid; pKa + log [base]/[salt] for a weak base. theseequations can be used to calculate.... - ANSWER - the pH of a buffer system if its composition is known
- the molar ratio of the component of a buffer system requires to give a solution of a desiredpH
- the change in pH of a buffered solution upon the addition of a given amount of acid or base what are the 3 categories that solution preparations fall into? - ANSWER simple solutions solutions by chemical reaction solution by extraction what are the 2 classifications of oral solutions? - ANSWER aqueous solutions non aqueous solutions aqueous solutions - ANSWER most common distilled or purified water is always used in preparing oral solutions -syrups -aromatic waters non aqueous solutions - ANSWER solvents other than water, either alone or in addition towater
- limited to a few solvents such as glycerin, alcohol, and propylene glycol what are 3 common non aqueous oral solutions? - ANSWER elixers spirits tinctures
what are some properties of oral syrups - ANSWER concentrated, viscous, sweetened, aqsolutions contain less than 10% alcohol
what are medicinal syrups, and when are they commonly used? - ANSWER they contain a drugex guaifenesis syrup
commonly used in pediatric dosage forms preparation of syrups - ANSWER heat - ingredients must be stable; fastest method agitation - heat labile ingredients; slower method in either case typically dissolve drug in water or other solvent mix with syrup what are aromatic waters used for? - ANSWER flavouring or perfuming agents what are properties of elixers? - ANSWER clear, sweetened hydro alcoholic (water and ethylalcohol) solution intended for oral use
what is the % range of alcohol for most elixers? - ANSWER can be 3-44% mostly 5-10% elixers that contain less than 10-12% alcohol requires the addition of an antimicrobialpreservative
compared to syrups, what is the sweetness and viscosity of elixers? - ANSWER less sweet andless viscous, generally less effective at masking taste
preparation of an elixer - ANSWER dissolve alcohol soluble ingredients in required volume ofalcohol; dissolve water soluble ingredients in part of the volume of water
How are tinctures prepared - ANSWER by percolation or maceration miscellaneous oral solutions - ANSWER usually aq (ie no alcohol) and may be sweetened butnot to the same extent as syrup or elixer
tend to be more concentrated with respect to the active ingredient, and therefore a smallervolume is administered per dose
these solutions are often administered by drops diluted in juice or water ex potassium iodideoral solution USP
compared to syrups, elixers are generally... - ANSWER less sweet less viscous less effective in masking taste always contain alcohol (disadvantage) advantages of elixers compared to syrups - ANSWER easier to prepare dissolves drug more easily better physical and chemical stability Liniments - ANSWER cutaneous application formed from alcohol or oil solvents may be a solution or emulsion -alcohol liniments used for counterirritant, rubefacient, and penetrating effects -oily liniments used for protective coating preparation to be applied with friction
for external use only what are collodions (paints) - ANSWER solutions designed for application to skin in smallquantities are called paints -leave film when dried containing drug
- usually 4% pyroxylin in 3:1 ether/alcohol ex salicylic acid collodion for warts What are douches? and the usual pH range - ANSWER aq solutions designed for application toa specific body part or cavity
3.8-4.4, vaginally can be up to 5.5 pH most common douche location - ANSWER vaginal examples of douches used for cleaning, antiseptic agents - ANSWER - eye douche to removeforeign particles/discharge
- pharyngeal douche: prep interior throat for surgery/cleanse
- bladder douche MUST BE STERILE
- nasal douch
- not an official class of prep in compendia what is an Enema - ANSWER a solution introduced into the rectum for cleansing, therapeuticor diagnostic purposes
what are the 2 types of enemas? - ANSWER evacuation: cleansing in situations of constipation
antimicrobials and flavouring agents what are the 5 main excipients of mouthwashes? - ANSWER - alcohol (10-20%)
- humectants (5-20%); promote water retention
- surfactants (between 0.1-0.5%)
- flavours
- colours what do nasal drops/solutions generally contain to relieve congestion? - ANSWERvasoconstrictors to relieve nasal congestion
they also contain antioxidants and antimicrobial preservatives its important that nasal products don't interfere with cilial movement; therefore productsshould be: - ANSWER isotonic: exert same osmotic pressure as body fluids buffered: used to resist changes in pH (strongly alkaline solutions can cause significantdamage to the cilia) similar viscosity to nasal mucous advantage of nasal spray over drops - ANSWER more wide spread coverage covers entire nasal cavity and upper throat area what are inhalations? - ANSWER drugs or solutions of drugs administered by nasal or oralrespiratory route
inhalation drugs may be administered for local action in the __________ ________ or for systemiceffects through absorption from _________ - ANSWER bronchial tree; lungs
What are metered-dose inhalers (MDIs)? - ANSWER drug formulated as a solution in a suitableliquified gas propellent (non aq solution) and co-solvent (if necessary)
benefit of MDI vs nebulizer - ANSWER more uniform dosing What are inhalants? - ANSWER special class of inhalations drug or combination of drugs that have sufficiently high vapour pressure that they can becarried by air currents into nasal passage -no need for solvent -amyl nitrate (angina) what are otic solutions for? - ANSWER administered to the ear as drops, also called ear oraural preparations
what are the 3 main classes of drugs used in otic solutions? - ANSWER - analgesics oranaesthetics
- antibiotics
- anti-inflammatory agents what are examples of additives? - ANSWER non medicinal ingredients -flavours
- sweeteners
- colours
- preservatives
- antioxidants
- buffers
