the hidden withdrawal: alcohol under the syrup
In actual fact the seizure—a kind of synaptic firefight in Poor Tony’s desiccated temporal lobes—was caused entirely by Withdrawal not From Heroin but from plain old grain alcohol, which was Codinex Plus cough syrup’s primary ingredient and balm. He’d consumed upwards of sixteen little Eighty-Proof bottles of Codinex per day for eight days, and so was cruising for a real neurochemical bruising when he just up and stopped.
Context
The theme's grim mechanism-reveal: the substitute meant to soften heroin-kicking had quietly made him a second addict, and it is alcohol-Withdrawal — "sixteen little Eighty-Proof bottles" a day — not opiate-Withdrawal that produces the grand-mal seizure. The bargain of 0301 pays out here: the corridor-extender didn't just prolong the agony, it installed a new, more dangerous dependency underneath the first, so that quitting the "medicine" is itself lethal. Detox from alcohol, unlike from opiates, can kill you — the datum the scene turns on.