Seizures refractory to conventional treatment are hallmarks of<unk> 
Clinical history is extremely important in evaluating for<unk>  (i.e. dosing history, duration of treatment, estimated dose taken)
Elevated anion-gap metabolic acidosis with elevated lactate in the appropriate clinical setting AND refractory seizures should raise suspicion
INH levels can be measured but results may not immediately be available
Isoniazid toxicity
Theophylline toxicity
Arsenic toxicity
Ipecac toxicity
Mold toxicity
Xylazine toxicity
Aluminum toxicity
Paraquat toxicity