the other. When circumstances produce a feeling of doubt on the part of the pharmacy technician, the  prescribing  physician  should  be  consulted. PHYSICAL Physical   incompatibilities   are   often   called pharmaceutical   incompatibilities   and   are   evi- denced  by  the  failure  of  the  drugs  to  combine properly.  It  is  virtually  impossible  for  uniform dosages of medicine to be given from such solu- tions  or  mixtures.  Ingredients  such  as  oil  and water,  which  are  physically  repellant  to  each other,  and  substances  that  are  insoluble  in  the prescribed   vehicle   are   primary   examples   of physical  incompatibilities. CHEMICAL This type of incompatibility exists when agents are prescribed that react chemically when mixed, altering  the  composition  of  one  or  more  of  the constituents. MANIFESTATIONS  OF INCOMPATIBILITY l l l l l l l l l Insolubility of prescribed agent in vehicle (physical) Immiscibility   of   two   or   more   liquids (physical) Precipitation due to change in menstrum that results in decreased volubility is called salting out (physical) Eutexia—the liquefaction of solids mixed in dry state (physical) Cementation  of  insoluble  ingredients  in liquid  mixtures  (physical) Evolution  in  color  (chemical) Oxidation-reduction or explosive reaction (chemical) Precipitation   due   to   chemical   reaction (chemical) Inactivation  of  sulfa  drugs  by  procaine HCl  (therapeutic) 8-18 Corrective  Measures l l l l l Addition  of  an  ingredient  that  does  not alter the therapeutic value, such as the ad- dition of an ingredient to alter volubility of  an  agent Omission   of   an   agent   that   has   no therapeutic value, or that maybe dispensed separately Change  of  an  ingredient.  Minor  changes such as a soluble form of an ingredient for an  insoluble  form  are  included. Change  of  a  solvent The  utilization  of  special  techniques  in compounding PRACTICAL   PHARMACY PROCEDURES COMPOUNDING Read the prescription, formula, or recipe carefully.  Be  sure  you  understand  its contents. Make sure that all ingredients required are on  hand,  in  the  quantities  required. Any substitutions or changes must be ap- proved  by  the  prescriber  and  initialed. As you weigh or measure each ingredient, check it off the prescription. If any doubt exists as to what or how much has been used, discard and begin again. [t is better to waste some material than to chance a faulty  medication. Be  neat,  precise,  and  methodical  when compounding  drugs.  Haste  not  only  makes waste  here—it  also  endangers  the  patient. Adhere to the sequences of compounding the  ingredients  and  the  techniques  pre- scribed by the formula or recipe—there is a  reason,  otherwise  they  would  not  be specified. Strive  for    “pharmaceutically  elegant” results,  such  as  smooth creams,  devoid  of  lumps solution;  etc. ointments  and and  grit;  clear