When it is used as an antiviral medicine, the most common side effects with Norvir (seen in more than 1 patient in 10) are taste perversion (a bad taste in the mouth), circumoral and peripheral paraesthesia (abnormal sensations around the mouth, or in the hands or feet), headache, abdominal (tummy) pain, nausea (feeling sick), diarrhoea, vomiting and asthenia (weakness).