Could you tell me about the side effects of this drug called gentamicin? I work in a geriatric home and was caring for this lady who just started gentamicin. She suffered from diarrhea, nausea, and was feeling so weak that she could hardly get out of bed - she was a lot more energetic before starting the gentamicin. Are these side effects of the gentamicin, and what can be done about these? Do you think that the lethargy this lady was experiencing is dangerous at all? When a woman in her 80s starts acting that way, it is easy to get worried!