Am.  Jour.  Pharm.  \ 
October,  1909.  J 
Assay  of  Heart  Tonics. 
467 
H.T.U.s  per  c.c.  Three  and  a  half  years  later  358  H.T.U.s.  Aver- 
age loss  about  10  per  cent,  yearly. 
A  very  important  point  should  be  noted  in  this  connection, 
namely,  the  menstruum  adopted  in  the  last  U.S. P.  for  the  preparation 
of  fluidextract  digitalis  is  much  less  desirable  than  the  U.S. P.  7th 
Revision  in  at  least  two  respects.  Repeated  trials  show  that  it  is 
almost  impossible  to  get  a  finished  product  containing  the  full  num- 
ber of  H.T.U.s  of  the  standard  we  had  previously  adopted,  the 
average  being  as  above  stated,  550  H.T.U.s  per  c.c,  while  with  drug 
of  the  same  quality  when  the  7th  Revision  menstruum  is  employed 
no  difficulty  is  experienced.  Owing  to  this  it  was  decided  to 
no  longer  attempt  to  assay  physiologically  the  8th  Revision  product 
and  to  take  such  statement  referring  to  it  off  the  label,  but,  in  order 
to  supply  the  medical  profession  with  a  full  strength  fluidextract  of 
the  drug,  it  was  decided  to  prepare  such  with  a  menstruum  contain- 
ing a  larger  per  cent,  of  alcohol  which  could  be  assayed  and  so 
labelled.  In  the  second  place  the  loss  in  potency  of  the  8th  Revision 
is  about  10  per  cent,  per  year,  while  with  the  7th  Revision  it  is  less 
than  one-half  as  great,  or  about  4  per  cent.  The  results  coincide 
quite  closely  with  those  following  the  change  made  in  the  menstruum 
for  the  fluidextract  of  squill  except  that  the  loss  in  activity  was 
greater  in  the  latter  drug,  as  pointed  out  (Houghton  in  the  J. A.M. A., 
June  12,  1906)  three  years  ago.  In  this  paper  several  methods  of 
physiological  assay  showed  very  clearly  that  a  serious  mistake  had 
been  made  in  changing  to  acetic  acid  as  a  menstruum.  The  writers 
feel  certain  that  any  one  who  has  tried  the  8th  Revision  menstruum 
for  fluidextract  digitalis  has  found  that  it  is  much  less  satisfactory 
from  a  pharmaceutical  point  of  view,  to  say  nothing  of  the  loss  in 
potency. 
4.  Tincture  digitalis,  U.S. P.  8th  Revision,  48.9  per  cent,  alcohol. 
The  average  strength  of  six  samples  was  found  to  be  at  the  time 
of  manufacture  7  H.T.U.s  per  c.c,  while  three  years  later  the 
strength  had  fallen  to  5  H.T.U.s  per  c.c,  or  an  average  yearly  loss 
of  9  per  cent.  While  the  number  of  samples  examined  may  not  be 
sufficient  for  drawing  final  conclusions,  it  seems  to  us  that  there 
is  no'  question  about  the  preparations  of  digitalis  losing  strength 
on  standing.  The  greater  the  per  cent,  of  alcohol  in  the  menstruum 
the  more  stable  the  product. 
The  experiments  to  determine  the  loss  in  potency  of  the  prep- 
arations of  digitalis  have  not  been  entirely  completed,  but  the 
