In general, alcohol will decrease the effectiveness of many antibiotics, as well as cause serious interactions.
Cephalexin comes from a category of medications called cephalosporins. Using alcohol and these cephalosporins together may cause abdominal or stomach cramps, nausea, vomiting, headache, dizziness or light-headedness, shortness of breath, sweating, or facial flushing. This reaction usually begins within 15 to 30 minutes after alcohol is consumed and usually goes away over several hours .
It cannot be predicted if this reaction will happen to you specifically, but it is a possibility.
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