A neurosurgeon was charged with murdering his Demerol-addicted wife with an overdose of the pain-killing narcotic, and the man's brother, an orthopedic surgeon, was charged as an accessory to murder. Dr. Stephen Marcus Levine, 42, formerly of Tarzana, allegedly issued more than 225 Demerol prescriptions--made out to a fictitious person--to his wife, Myrna Levine, 32, during the last 14 months of her life. Myrna Levine, a known Demerol addict, died in May, 1984, in her Tarzana home from an overdose, Deputy Dist. Atty. Robert Dawson said. An autopsy reportedly detected a level of Demerol in her body 24 to 48 times the amount that would be present under normal medical use. The prosecutor said Levine's brother, Dr. David Lawrence Levine, 43, allegedly signed his sister-in-law's death certificate listing the cause of death as cardiac arrest and a seizure disorder. Both men pleaded not guilty to the charges and were freed on bail.