The actual symptoms of an Ambien overdose will differ from person to person but the drug has common effects that are seen. For example, the most common reported symptoms include excessive tiredness, sleepiness, light coma, heart failure, respiratory failure, lung failure, nausea, vomiting, hallucinations, impaired judgment and reasoning, headaches, short term memory loss, and anterograde amnesia. The actual symptoms will also differ according to the actual amount of Ambien overdose dosage that the patitne has taken.