Final answer:
Phenelzine is a monoamine oxidase inhibitor that can cause serotonin syndrome when combined with other medications.
Step-by-step explanation:
Phenelzine is a monoamine oxidase inhibitor (MAOI) commonly used as an antidepressant. The symptoms described - hyperreflexia, hypertension, and coma - are indicative of a condition called serotonin syndrome, which is caused by excessive serotonin activity in the brain.
While phenelzine inhibits the breakdown of serotonin, another medication commonly seen in cases of serotonin syndrome is meperidine (also known as Demerol), an opioid pain medication. The combination of phenelzine and meperidine can lead to an accumulation of serotonin, producing the symptoms experienced by the patient.
Therefore, the most likely cause of the symptoms in this case is the concurrent use of phenelzine and meperidine.