Antony's act be deemed the proximate cause of Cleo's death?

Antony gives Cleopatra a gl of wine tainted with arsenic, intending to kill her. However, the poison does not instantly kill her. ume that Cleo refused to go to the hospital - even though she knew she would not otherwise likely recover from the poison. She died several hours later. Will Antony's act be deemed the proximate cause of Cleo's death?