Calomel
$1/dose. LC4. TL5 according to bio-tech but feels too late.
The chemical mercurous chloride, or calomel, causes vomiting and diarrhea, treat as Arsenic if used as an overdose - but toxic damage totaling half or more of HP in one course of treatment loosens the teeth; roll vs. HT. One tooth falls out for each point in the margin of failure. Treat overdoses as Arsenic.