In some rabbit studies, an overall overnatter bactrim bestill increase in fetal loss dead and resorbed and malformed conceptuses was associated with doses of trimethoprim times the human therapeutic dose. Posted by LoriFLA at 7:45 PM on January 1, 2007 Real simple-like, but not even approaching comprehensive: antibiotics are prescribed to cover specific organisms. SEPTRA is also contraindicated in pregnant patients at term and in nursing mothers, because sulfonamides pass the placenta and are excreted in the milk and may cause kernicterus. When used prudently, antibiotics are powerful medical tool to thwart bacterial diseases. Both trimethoprim and sulfamethoxazole exist in the blood as unbound, protein-bound and metabolized sulfamethaxazole also exists as the conjugated form.