Susceptible bacteria
According to the product package insert, ofloxacin is effective against these microorganisms:Aerobic Gram-positive microorganisms:

Staphylococcus aureus (methicillin-susceptible strains)
Streptococcus pneumoniae (penicillin-susceptible strains)
Streptococcus pyogenesAerobic Gram-negative microorganisms 

Citrobacter koseri (Citrobacter diversus)
Enterobacter aerogenes
Escherichia coli
Haemophilus influenzae
Klebsiella pneumoniae
Neisseria gonorrhoeae
Proteus mirabilis
Pseudomonas aeruginosaOther microorganisms:

Chlamydia trachomatis

Adverse effects
In general, fluoroquinolones are well tolerated, with most side effects being mild to moderate. On occasion, serious adverse effects occur. Common side effects include gastrointestinal effects such as nausea, vomiting, and diarrhea, as well as headache and insomnia. The overall rate of adverse events in patients treated with fluoroquinolones is roughly similar to that seen in patients treated with other antibiotic classes. A U.S. Centers for Disease Control study found patients treated with fluoroquinolones experienced adverse events severe enough to lead to an emergency department visit more frequently than those treated with cephalosporins or macrolides, but less frequently than those treated with penicillins, clindamycin, sulfonamides, or vancomycin.Postmarketing surveillance has revealed a variety of relatively rare but serious adverse effects associated with all members of the fluoroquinolone antibacterial class. Among these, tendon problems and exacerbation of the symptoms of the neurological disorder myasthenia gravis are the subject of "black box" warnings in the United States. The most severe form of tendonopathy associated with fluoroquinolone administration is tendon rupture, which in the great majority of cases involves the Achilles tendon. Younger people typically experience good recovery, but permanent disability is possible, and is more likely in older patients. The overall frequency of fluoroquinolone-associated Achilles tendon rupture in patients treated with ciprofloxacin or levofloxacin has been estimated at 17 per 100,000 treatments.
"A number of the endogenous compounds have been reported to be affected by ofloxacin as inhibitors, alteraters, and depletors. See the latest package insert for ofloxacin for additional details. Mode of action
Ofloxacin is a broad-spectrum antibiotic that is active against both Gram-positive and Gram-negative bacteria. It functions by inhibiting two bacterial type II topoisomerases, DNA gyrase and topoisomerase IV. Topoisomerase IV is an enzyme necessary to separate (mostly in prokaryotes, in bacteria in particular) replicated DNA, thereby inhibiting bacterial cell division. History
Ofloxacin is a second-generation fluoroquinolone, being a broader-spectrum analog of norfloxacin, and was synthesized and developed by scientists at Daiichi Seiyaku.It was first approved for marketing in Japan in 1985, for oral administration, and Daiichi marketed it there under the brand name Tarvid. Daiichi, working with Johnson & Johnson, obtained FDA approval in December 1990, under the brand name Floxin, labelled for use in adults with lower respiratory tract infections, skin and skin structure infections, urinary tract infections, prostatitis, and sexually transmitted diseases.