Q: After few minutes of getting first dose of Metronidazole, patient developed tachycardia, fever, shivering, sweating, dilated pupils, twitching, hyper-reflexia, hyperthermia. Patient became confused, agitated and hypertensive. Your concern?

Answer: Serotonin Syndrome from metronidazole

Symptoms of Serotonin syndrom has been reported with metronidazole. Treatment is discontinuation of drug and supportive treatment.

Reference:

Karamanakos, P. N. (2008). "The possibility of serotonin syndrome brought about by the use of metronidazole". Minerva Anestesiologica 74(11): 679.