<prompt> Strength of topical ophthalmic preparations of tobramycin is : September 20093 mg ml8 mg ml10 mgml13 mgml  <response>: Ans. A: 3 mgml Tobramycin works by binding to a site on the bacterial 30S and 50S ribosome, preventing formation of the 70S complex. As a result, mRNA cannot be translated into protein and cell death ensues. Sterile Tobramycin Ophtha Solution eye-drops contains tobramycin concentration of 0.3. It is mixed with 0.01 benzalkonium chloride as a preservative. This concentrations result in 3 mg per ml. 