Which of the following is not a possible adverse reaction to Levaquin (levofloxacin)?

Levaquin, or levofloxacin, is known for its association with several adverse reactions due to its classification as a fluoroquinolone antibiotic. Among the various potential side effects, Achilles tendon rupture, peripheral neuropathy, and nephrotoxicity are well-documented risks.

Achilles tendon ruptures are particularly concerning in older adults and those taking concurrent corticosteroids. Peripheral neuropathy involves damage to the peripheral nerves and is another recognized complication linked with fluoroquinolones, which can lead to varying degrees of symptoms such as pain, tingling, or weakness in the limbs. Nephrotoxicity indicates kidney damage which can occur as a side effect of many medications, including fluoroquinolones, though it is less commonly reported compared to the other risks.

On the other hand, while Stevens-Johnson syndrome is a serious skin reaction that can arise from various medications (including some antibiotics), it is not prominently associated with levofloxacin. This makes it the least likely adverse reaction listed in the choices, confirming it as the correct answer to the question regarding adverse effects of Levaquin.