^°^"juiy''i88^^'*™'}      Incompatibilities  in  Prescriptions.  351 
NOTES  ON  INCOMPATIBILITIES  IN  PEESCRIPTIONS.^ 
By  H.  Campbell,  Pharmaceutical  Chemist. 
The  author  said  that  some  persons  consider  that  all  drugs  which 
react  chemically  are  incompatible,  and,  therefore,  are  led  to  condemn 
mixtures  of  tinct.  hyoscyami  with  liquor  potassse,  of  liq.  ferri  per- 
chlor.  with  glycerin,  of  qainine  sulphate  with  alkalies,  or  of  liq.  plumbi 
subacet.  with  tinct.  opii.  But  probably  all  present  had  dispensed  such 
combinations  to  the  entire  satisfaction  of  the  prescribers.  In  dealing, 
however,  with  presumably  incompatible  prescriptions,  it  was  necessary, 
generally  speaking,  to  rely  on  the  following  rules : 
1st.  If  any  dangerous  decomposition  may  be  expected  to  occur  after 
the  medicine  has  left  the  dispenser,  some  precaution  should  be  taken 
to  obviate  such  danger,  and  in  most  cases  that  precaution  would  take 
the  form  of  a  warning  to  the  prescriber. 
2d.  To  dilute  the  suspected  ingredients  before  mixing,  or,  in  the 
language  of  the  dispensing  counter,  to  keep  them  apart  as  far  as 
possible.'^ 
3d.  To  mix  them  cold. 
4th.  When  strictly  necessary,  to  use  mucilage  (preferably  that  of 
tragacanth)  in  order  to  retard  decomposition,  or  to  suspend  a  precipitate. 
In  a  paper  read  before  a  medical  society,  the  following  mixture  had 
been  condemned  on  the  ground  that  as  the  first  two  ingredients  form  a 
well-known  alkaloidal  precipitant,  a  compound  containing  most  of  the 
mercury  will  fall,  and  be  taken  in  the  last  dose  : — 
R  Liq.  hyd.  perchlor  rci  10 
Potass,  iodid    gr.  10 
Dec.  cinchon  ad 
If,  however,  the  mixture  were  dispensed  according  to  the  second 
rule,  the  precipitate  was  so  readily  diffusible  and,  after  shaking,  re- 
mained suspended  so  long,  that  the  patient  had  plenty  of  time  to  pour 
out  a  dose ;  but,  of  course,  he  should  be  directed  to    shake  the  bottle.'' 
Again  it  is  considered  that  liq.  strychnine  must  not  be  combined 
with  sodium  bicarbonate,  yet  the  following  mixture  had  remained  clear 
for  weeks  : — 
R  Liq.  strychnine   tt^  5 
Sodii  bicarb  gr.  15 
M-  ad  
1  Abstract  of  a  paper  read  before  the  Midland  Counties  Chemists'  ilssocia- 
tion ;  reprinted  from  Fhar.  Jour,  and  Trans.,  May  12. 
