Hi, thanks for asking in Healthcare Magic. Adderall contains a mixture of Amphetamine amphetamine and Dextro-amphetamine. It is a mood elevator and also is given in Attention deficit disorder. Flourinated General anesthetics like Halothane, Enflurane and methoxyflurane interact with Amphetamine by sensitizing heart to the effects of Amphetamine which can result in arrhythmia. These drugs are called general anesthetics as they result in reversible loss of conciousness. But you have mentioned that it is going to be a twilight sleep which means Dissociative Anesthesia or Conscious Sedation , characterized by profound analgesia, light sleep and a feeling of dissociation. The drug Ketamine is given to induce dissociative anesthesia. This does not interact with Adderall. You have taken Adderall 20 mg, 17 hours before surgery. It is not the toxic dose.The elimination half life (time taken for the drug to be excreted completely from body) of Amphetamine is 20 hours and that of Dextroamphetamine is 11 hours. So nearly 90% of Adderall would have been eliminated before anesthesia. Acidification of urine with ammonium chloride will increase the excretion of Amphetamine and Dextroamphetamine and are given in overdose of these drugs to eliminate them completely from the body. Otherwise you can take some fruit juices which also will acidify the urine and will help in elimination of Adderall from your system I hope this is useful to you.