Here is some information on how little alcohol is known to cause this unpleasant reaction
How the interaction occurs:
Metronidazole and tinidazole cause an intolerance to alcohol by altering how the body breaks down alcohol. Many medicines (prescript
ion and nonprescript
ion), mouthwashes, and aftershaves contain alcohol.
Even a small amount of alcohol (e.g. 15 ml or one tablespoon) can trigger the effects.
What might happen:
Ingesting alcohol or using topical preparations that contain alcohol may result in throbbing in the head and neck, irregular heart beat, rapid heart beat, low blood pressure, sweating, nausea, and vomiting.
This interaction may last from 30 to 60 minutes to several hours, depending on the amount of alcohol consumed.
What you should do about
this interaction:
If possible, avoid the use of medicines that contain alcohol when using metronidazole. Use of topical products such as creams or lotions that contain alcohol may also cause this interaction. The amount of alcohol required to cause this interaction varies with individuals.
FROM
www.webmd.com/drugs/2/drug-91258/tinidazole-oral/details/list-interaction-details/dmid-1361/dmtitle-metronidazole-tinidazole-ethyl-alcohol/intrtype-drug