Final answer:
The two most common drugs for gram-negative GI coverage are ciprofloxacin and trimethoprim/sulfamethoxazole, which have broad-spectrum activities and are effective against many gram-negative organisms.
Step-by-step explanation:
The two most common drugs for gram-negative GI coverage are typically ciprofloxacin and trimethoprim/sulfamethoxazole. These drugs have a broad spectrum of activity that includes many gram-negative bacteria commonly found in the gastrointestinal tract, such as those from the family Enterobacteriaceae. Ciprofloxacin is a fluoroquinolone that was not widely available until the 1980s, and is effective against a variety of gram-negative organisms. Trimethoprim/sulfamethoxazole, also known as co-trimoxazole, combines two antibiotics to inhibit successive steps in the folate synthesis pathway of bacteria, offering a synergistic and broad-spectrum antibacterial effect.