American Chronicle Christina England August 02, 2009. Severe stomach cramps, nightmares, hallucinations, diarrhoea, strange behaviour, suicide, and death, these are all known side effects that have been linked with the antiviral drug Tamiflu, over the recent months. User Reviews for Tamiflu. The following information is NOT intended to endorse drugs or recommend therapy. While these reviews might be helpful, they are not a substitute for the expertise, skill, knowledge and judgement of healthcare practitioners in patient care. The government's chief medical officer Sir Liam Donaldson has said Tamiflu should still be given to children, despite more than half of young recipients who take the drug suffering side effects. Summary. Bad dreams is found among people who take Tamiflu, especially for people who are male, 2-9 old , have been taking the drug for 1 month, also take medication Acetaminophen, and have H1n1 influenza. Since Japan uses far more Tamiflu than any other country, it's possible that these side effects are simply so rare that they only occur when prescriptions pass a certain threshold. The flu itself or Tamiflu may rarely cause serious mental/mood changes. This may be more likely in children. Tell your doctor of any signs of This may be more likely in children. Tell your doctor of any signs of unusual behavior , including confusion , agitation, or self-injury. Can Tamiflu cause Nightmares? Nightmares is a known side effect of Tamiflu. Complete analysis from patient reviews and trusted online health resources, including first-hand experiences. - Page 3 Nightmares is a known side effect of Tamiflu. LONDON, England (CNN) -- More than half of children taking antiviral drug Tamiflu suffer side-effects such as nausea, insomnia and nightmares, UK researchers have said. Almost one in five (18 per cent) reported a neuropsychiatric side effect , such as poor concentration, inability to think clearly, problems sleeping, feeling dazed or confused, bad dreams or. Tamiflu (oseltamivir) is a prescription medication which can cause side effects during the course of your treatment. Not everyone experiences side effects, but they can occur at any stage as individuals will react differently to the medication, although it is more likely to occur early on in the treatment.