2 The technology

2.1 Rifaximin (Targaxan, Norgine) is a semi‑synthetic derivative of the antibiotic rifamycin. Rifaximin decreases intestinal production and absorption of ammonia, which is thought to be responsible for the neurocognitive symptoms of hepatic encephalopathy, thereby delaying the recurrence of acute episodes. Rifaximin has a marketing authorisation in the UK 'for the reduction in recurrence of episodes of overt hepatic encephalopathy in patients aged 18 years or older'. The summary of product characteristics highlights that 91% of people in the pivotal study were using concomitant lactulose.

2.2 The summary of product characteristics lists the following common adverse reactions for rifaximin: depression, dizziness, headache, dyspnoea (shortness of breath), upper abdominal pain, abdominal distension, diarrhoea, nausea, vomiting, ascites (accumulation of fluid in the abdominal cavity), rashes, pruritus (itching), muscle spasms, arthralgia (joint pain), and peripheral oedema (swelling). For full details of adverse reactions and contraindications, see the summary of product characteristics.

2.3 Rifaximin is available as 550 mg film‑coated tablets at a net price of £259.23 per 56‑tablet pack (excluding VAT; British national formulary online [accessed December 2014]). It is administered orally at a recommended dose of 550 mg twice daily. The company estimated an average cost of £1689.65 for 6 months of treatment. Costs may vary in different settings because of negotiated procurement discounts.