Pharmaceutics Lab Lecture Conceptual Material

Pharmaceutics Lab Lecture Conceptual Material Isotonicity Osmotic Pressure-pressure responsible for the movement of the solvent into the more concentrated solution until equilibrium is established on both sides Isosomotic-having an equal pressure to that of physiologic fluids -physiochemical term comparing osmotic pressures of 2 liquids that may or may not be physiologic fluids Isotonic-equal tone; used w/ reference to a specific body fluid Ex. 0.9% NaCl Hypotonic-soln w/ lower osmotic pressure than body fluids or 0.9% NaCl soln Ex. 0.1% NaCl Hypertonic-soln w/ greater osmotic pressure than body fluids or 0.9% NaCl soln Ex. 3% NaCl Hemolysis-swell and burst; A hypertonic soln induces hemolysis of RBC passage of water from the site of an ophthalmic application thru the tissues of the eye -hemolysis is more severe b/c it releases the cell contents and can’t be fixed Crenation-shrinking; In blood stream, a hypertonic injection can cause crenation of blood cells; in the eye, the soln can draw water toward the site of the topical application NaCl Equivalent Method: 1. Determine how much drug is needed for the formula 2. Determine how much NaCl is eqv to the amount of drug (multiply by E value) 3. Determine how much NaCl needed to make formula isotonic 0.9%=x/total 4. Determine how much NaCl you should weigh: step 3 – step 2 -if NaCl is not the chemical you are using, divide by that chemical’s E-value Freezing Point Depression Method: 1. Determine the percent of drug in the formula 2. Determine the D-value of the chemicals (proportion 1%/0.14 = 1.5%/x) 3. Subtract chemical’s D-value from 0.52 4. Determine percent of chemical needed to make soln isotonic (1%/.58=x/.31) 5. Convert to weight: 0.534/100 = x/60 x = 321mg Freezing Point Depression Method using another chemical: *complete steps 1-3 from above as previously done 4. Determine percent of chemical needed to make soln isotonic (1%/.29=x/.31) 5. Convert to weight: 1.07/100 = x/60 x = 641mg Water freezes at 0 C; lacrimal fluid/blood freeze at -0.52 C; FP depression of lacrimal fluid is 0.52; Anything with FPD of 0.52 is isontonic.

Suppositories -Solid dosage forms intended for insertion into body cavities where they melt, soften, or dissolve and exert local or systemic effects Rectal-cylindrical w/ one or both sides tapered (bullet, torpedo, or little finger); adult supp ~ 2g; 32 mm Vaginal (pessary)-oviform, globular or cone-shaped; 5g Urethral (bougies)-slender, pencil-shaped Males-4g; 3-6mm Females-2g; 70mm Advantages over oral medications: -avoid pH/enzymatic activity of the stomach or intestines -don’t cause stomach irritation -avoids 1st pass effect of liver -convenient for patients that are unable to swallow -effective fore treating patients who are vomiting Fatty bases (Cocoa butter, Fattibase): Melt just below body temp. Caution with over heating cocoa butter (may cause crystals to form upon cooling) -good to use with hydrophilic drugs Water-soluble bases (Glycerinated gelatin/PEG): Used vaginally, slower to soften, tendency to absorb moisture may dehydrate and irritate tissues -do not melt at body temperature, dissolve slowly in body fluids -good to use with hydrophobic drugs -PEG-various molecular weights mixed to achieve desired consistency Miscellaneous Bases-mixtures of fatty and water-soluble bases Methods of Compounding Molding-base and drug melted, poured into mold and cooled Compression-mixture forced into a mold Hand rolling-little requirement for today’s pharmacists Density Displacement Factor -must account for it when the drug amount is > 5% of the total suppository weight Preparation of Gel Formulas using Carbopol: -the carbopols 934, 940 and 941 are synthetic polymers with high MWs and many free carboxyl groups; When the relatively poorly water soluble powder is dispersed in water, the pH is very acidic (2-3). Addition of alkali (sodium hydroxide, sodium carbonate, or triethanolamine) will increase the pH to 5-7 with a substantial increase in soln viscosity. Carbopol 934-gelly agent, increases viscosity, thickening agent Methyl Salicylate (aka oil of wintergreen)-cooling sensations, active ingr, counter-irritant Triethanolamine-increases pH (5-6), causes gels to form Advantage of alcohol: non-drip, kills germs, cools, dries fast, more soluble, cooling Disadvantage of alcohol: absorbs water, smells, increases irritation, costs more than water