That Chloral Hydrate or whatever it is...is an hypnotic drug.
So is this other drug (i'm still googling) called GHB aka Somatomax. Wasn't Anna taking something called Soma something? This drug causes seizures and coma. This article says it has a salty soapy taste but that is easily masked. And no trace of it is left in the urine after 12 hours:
http://www.erowid.org/chemicals/ghb/ghb_journal25.shtml
An excerpt:
Symptoms of GHB overdose include vomiting, bradycardia, coma, clonic muscle movements, induction and emergence delirium, and Cheyne-Stokes respiration. Diagnosis depends on history at the scene, and treatment is aimed at protecting the airway. The high incidence of vomiting carries with it a high risk of aspiration, said Dyer. Benzodiazepines and opiate antagonists are not effective... The drug is undetectable in the urine after 12 hours. A level teaspoon contains 2.8 g, but since the drug is now made clandestinely it is often far from pure.