Hello, Hallucinations are a rear side effect of Sulfamethoxazole so it can be that your husband has developed hallucinations due to its use. Also, the fact that he started to have hallucinations a few days after starting Sulfamethoxazole, while he did not have these previously, is another indicator that they are related. I would say that he needs to stop Sulfamethoxazole and let his doctor know as soon as possible. Other antibiotics can be prescribed to help with the urinary infection. I hope this answers your query. I remain at your disposal for further medical assistance. Regards, Dr. Antoneta Zotaj General and Family Physician