790 
Mode  of  Action  of  Common  Laxatives. 
(  Am.  Jour.  Pharm. 
I       Nov.,  1921. 
of  laxative  drugs  by  the  laity.  Sometimes  they  are  purchased  by 
the  public  with  a  distinct  appreciation  of  their  purpose;  not  in- 
frequently potent  laxatives  represent  an  essential  ingredient  of  pro- 
prietary and  "patent"  medicines  that  are  secret  as  to  composition 
and  misrepresented  with  respect  to  their  pharmacology.  Probably 
physicians  would  be  more  discriminating,  or  at  least  more  rational 
in  the  prescription  of  the  various  laxative  preparations,  if  informa- 
tion regarding  the  pharmacodynamics  of  the  subject  were  more 
widely  disseminated  among  the  members  of  the  profession. 
Calomel  is  a  popular  representative  of  the  group  of  non-saline 
laxatives.  It  has  currently  been  represented  to  act  by  promoting  in- 
testinal secretion  and  retarding  absorption,  so  that  an  accumulation 
of  the  abundant  fluid  and  a  consequent  evacuation  of  semisolid  con- 
tents ensues.1  A  recent  investigation  of  the  pharmacologic  action 
of  calomel,  aided  in  particular  by  roentgen-ray  observations  of  the 
progress  of  the  alimentary  reactions  has  not  substantiated  the  view 
just  cited.  Working  in  the  pharmacologic  institute  of  the  Uni- 
versity at  Utrecht  van  der  Willigen2  has  concluded  that  absorption  in 
the  gastro-intestinal  canal  is  not  interfered  with  in  the  presence  of 
calomel.  The  drug  functions  by  promoting  more  vigorous  move- 
ments of  the  small  and  large  intestines  whereby  the  contents  are 
propelled  so  rapidly  toward  the  rectum  that  absorption  and  the  pro- 
duction of  formed  stools  cannot  take  place.  The  fundamental  fea- 
ture in  the  action  of  calomel  therefore,  is  its  influence  on  alimentary 
peristalsis. 
The  widely  used  phenolphthalein,  the  laxative  action  of  which 
was  an  accidental  discovery  of  pharmacology,  is  another  drug  which 
promotes  peristalsis  so  that  fluid  contents  are  driven  into  the  proxi- 
mal colon  more  rapidly  than  under  normal  circumstances.  Van  der 
Willigen  has  recently  demonstrated  that  the  drug  does  not  retard 
absorption,  nor  does  it  produce  secretion  in  undue  quantities,  as  is 
currently  taught.  In  connection  with  this  laxative  also,  then,  our 
present  day  assumptions  must  be  revised. 
How  sulphur  acts  to  promote  purgation  has  been  considerably 
debated.  One  investigator,  for  example,  has  believed  that  it  gives 
1  Meyer,  H.  H.,  and  Gottlieb,  R. :  Experimentelle  Pharmakologie,  Ed.  4, 
Vienna,  1920. 
2  Van  der  Willigen,  A.  M.  M. :  Die  Abfiihrwirkung  des  Kalomels,  Arch, 
f.  d.  ges.  Physiol.  186:  185,  1921. 
