Method for providing a cathartic effect

1. A compound represented by the formula (IV):

wherein L is oxo and M is hydroxy;

A is —COOH;

B′ is —CH 2 —CH 2 —;

Z is

wherein one of R 4 and R 5 is hydrogen and the other is hydroxy;

R 1 is a —(CH 2 ) 6 — straight chain;

X 1 ′ and X 2 ′ are halogen atoms;

R 2 is a single bond; and

R 3 is lower alkyl.

2. The compound as described in claim 1 , wherein said compound is 13,14-dihydro-16,16-difluoro-prostaglandin E1.

3. The compound as described in claim 1 , wherein X 1 ′ and X 2 ′ are fluorine atoms.