By THE ASSOCIATED PRESS WASHINGTON, Sept. 4 (AP) - A time-released medication used to prevent heartworm in millions of dogs was recalled Friday at the request of the Food and Drug Administration after thousands of dogs suffered adverse reactions. The medication, ProHeart 6, is the only product approved by the agency to be administered twice a year to treat the disease in dogs. Its active ingredient, moxidectin, has been administered without problem to horses and cattle. The time-released version caused few problems when given to dogs at higher doses in clinical trials. Health and safety problems quickly cropped up, however,...