Metronidazole is listed as a possible carcinogen according to the World Health Organization (WHO) International Agency for Research on Cancer (IARC). A study in those with Crohns disease also found chromosomal abnormalities in circulating lymphocytes in people treated with metronidazole. Stevens–Johnson syndrome
Metronidazole alone rarely causes Stevens–Johnson syndrome, but is reported to occur at high rates when combined with mebendazole. Drug interactions
Alcohol
Consuming alcohol while taking metronidazole has been suspected in case reports to cause a disulfiram-like reaction with effects that can include nausea, vomiting, flushing of the skin, tachycardia, and shortness of breath. People are often advised not to drink alcohol during systemic metronidazole therapy and for at least 48 hours after completion of treatment. However, some studies call into question the mechanism of the interaction of alcohol and metronidazole,
and a possible central toxic serotonin reaction for the alcohol intolerance is suggested. Metronidazole is also generally thought to inhibit the liver metabolism of propylene glycol (found in some foods, medicines, and in many electronic cigarette e-liquids), thus propylene glycol may potentially have similar interaction effects with metronidazole. Other drug interactions
Metronidazole is a moderate CYP2C9 inhibitor. CYP2C9 is an enzyme of cytochrome P450 family. Therefore, metronidazole may interact with medications metabolized by this enzyme. Examples of such medications are lomitapide, warfarin, etc. Pharmacology
Mechanism of action
Metronidazole is of the nitroimidazole class. It inhibits nucleic acid synthesis by forming nitroso radicals, which disrupt the DNA of microbial cells.
The young and the elderly are at the highest risk of viral encephalitis. Many cases of viral encephalitis are not identified either because of lack of testing or mild illness, and serological surveys indicate that asymptomatic infections are common. Various ways of preventing viral encephalitis exist, such as vaccines that are either in standard vaccination programs or which are recommended when living in or visiting certain regions, and various measures aimed at preventing mosquito, sandfly, and tick bites in order to prevent arbovirus infection. Etiology
Many viruses are capable of causing encephalitis during infection, including:

Transmission
Encephalitic viruses vary in their manner of transmission. Some are transmitted from person-to-person, whereas others are transmitted by animals, especially bites from arthropods such as mosquitos, sandflies, and ticks, such viruses being called arboviruses. An example of person-to-person transmission is the herpes simplex virus, which is transmitted by means of intimate physical contact. An example of arboviral transmission is the West Nile virus, which usually is incidentally transmitted to people from the bites of Culex mosquitos, especially Culex pipiens. Pathogenesis
Viruses that cause viral encephalitis first infect the body and replicate outside of the central nervous system (CNS). Thereafter, most reach the spinal cord and brain via the circulatory system. Exceptions to this include herpesviruses and the rabies virus, which travel from nerve endings to the CNS. Once in the brain, the virus and the hosts inflammatory response disrupt neural cell function, including causing fluid buildup in the brain, vascular congestion, and bleeding.