Therapeutic dosage: toxicity values for most commonly monitored medications

"The magic 2s":
Digitalis (.5-1.5) Toxicity = 2.
Lithium (.6-1.2) Toxicity = 2.
Theophylline (10-20) Toxicity = 20.
Dilantin (10-20) Toxicity = 20.
APAP (1-30) Toxicity = 200.