What is Gaviscon Double Action Aniseed? Fast Powerful Relief from Heartburn & Indigestion. Sodium alginate. Sodium bicarbonate. Calcium carbonate. Works in 2 ways. Double Action Gaviscon Mixed berry brings long lasting relief from the pain and discomfort of heartburn and acid indigestion. It gets to work in two different ways: 1) neutralising excess stomach acid to relieve pain and discomfort.2) forming a protective barrier over the stomach contents to soothe the burning pain in your chest. This product is sugar free and gluten-free. How to take Gaviscon Double Action Aniseed For oral use. Shake well before use. Adults and children 12 years and over: Take 10-20ml (two to four 5ml spoonfuls) after meals and at bedtime, up to four times a day.