text: how much restoril is fatal?   restoril is the brand name for temazepam. it is a sleeping pill.   when used for treatment of insomnia, the usual dose is 7.5mg to 15mg taken at bedtime.  although not usually fatal when taken alone, a temazepam overdose is considered a medical emergency and generally requires the immediate attention of medical personnel. the lethal dose is not known, but supposed to be over 500 mg. a case of a person surviving after taking 300 mg is known.