Final answer:
Using tobramycin and gentamicin at the same time is problematic because their combined toxic effects can lead to increased risk of nephrotoxicity and ototoxicity. These antibiotics work in the same way, thus increasing side effects without adding therapeutic benefits. Instead, different antibiotics that target different mechanisms are preferred for synergistic effects.
Step-by-step explanation:
The reason why it is problematic to administer tobramycin and gentamicin at the same time is due to their similar mechanisms of action and side effect profiles. Both drugs are aminoglycoside antibiotics and can have potent effects against certain bacteria. However, when used together, their toxicities, particularly to the kidneys (nephrotoxicity) and to the ears (ototoxicity), can be additive, leading to an increased risk of serious side effects for the patient.
This is especially true since both drugs are cleared by the kidneys and can accumulate to harmful levels if the kidneys are not functioning well. Also, the risk of a 'superinfection' or secondary infection is increased when broad-spectrum antibiotics like these are used, as they can disrupt the normal microbiome and allow resistant bacteria to proliferate.
Furthermore, the simultaneous use of multiple antibiotics from the same class doesn't typically add to the therapeutic benefit but does add to the risk of side effects. In the treatment of serious infections where one antibiotic is not sufficient, combining drugs that work in synergistic ways or target different pathways in bacteria is preferable. For instance, a combination of ampicillin, nafcillin, and gentamicin is used for synergistic coverage of Staphylococcus spp. and Streptococcus spp., illustrating the careful selection of antibiotics to maximize the benefits and minimize the risks.