Sounds like DYNACIN
Generic Name
Minocycline HCl Tab 100 MG
but
the Imprint for this pill is
DYN-100 / 749
Any chance the G could be a D?
Mfg / Labeler MEDICIS
Color dark gray
Shape oblong
There is am image on the medicis.com website if you want to take a look.
Minocycline is a
tetracycline antibiotic. It fights bacteria in the body.
Minocycline is used to treat many different bacterial infections, such as urinary tract infections, acne etc.
More info at
http://minocycline.drugs.com