Re: Can we modify a drug in order to get only one of its side effects?

I'm sorry, Charles, but I can't speak to prostaglandins in particular. I 
can tell you that medicinal chemists are constantly working to identify 
structural analogs of known drugs that have either increased efficacy or 
reduced side effects. 

This work can be as simple as identifying a specific isomer in a mixture 
that has the desirable properties. One example of this is the release of 
Nexium (esomeprazole) by AstraZeneca to replace Prilosec (omeprazole) for 
the treatment of stomach acid release problems. Esomeprazole is simply 
the S isomer of omeprazole (this is reflected in the name).

A more complicated example is the hunt for drugs that replace the hormone 
estrogen, known as selesctive estrogen receptor modulators (SERMs). 
Ideally, SERMs would recapitulate all the beneficial effects of estrogen 
in women (increased bone density, healthy cholesterol balance, relieve 
hot flashes) without the potentially dangerous ones (increased risk of 
breast and uterine cancer). Because of the potential for use not only in 
cancer therapy and prevention, but also in hormone replacement therapy in 
post-menopausal women, SERMs are a very active area of research. For a 
layman's introduction to the action of estrogen and SERMs, I recommend 
this site from the National Cancer Institute:  http://r
ex.nci.nih.gov/behindthenews/uest/uestcontents.htm