Anything can "reduce autism symptoms" that can make a neurotypical person unable to behave normally. Autistic behavior IS the normal for autistic people. Heavy sedatives, just like being very sick, can "reduce autism symptoms" since the person would be too tired to exhibit any behaviors at all.
"Look, he's not flapping and pacing! His autism must be cured!" No, you dolt, he's exhausted and miserable from being sick.
Leave autistic people alone and let them be themselves. Seriously, I can't believe some people would rather let their kid die of polio than believe they could be autistic. If you think having an autistic child is that terrible, you probably shouldn't have kids.