ANTACIDS are agents used to neutralize gastric acid, so raising gastric pH. This inhibits peptic enzyme activity, which is greatly inhibited above pH 5. Antacids are useful for some sorts of hyperacidity causing the symptoms of dyspepsia, exacerbated by alcohol and NSAID drugs. Although antacids give symptomatic relief of the dyspepsia, gastritis and oesophagitis, there is little objective evidence of accelerated healing of peptic ulcers (gastric or duodenal). Antacids taken alone effectively reduce acidity, but are commonly combined with other drugs, e.g. GASTRIC SECRETION INHIBITORS, demulcents and antifoaming agents (see CARMINATIVES). Antacids themselves have some side-effects such as uncomfortable flatulence, diarrhoea or constipation: bicarbonates and carbonates tend to cause flatulence; some aluminium-containing antacids cause constipation; whereas magnesium-containing antacids can cause diarrhoea (so different types are often used in combination). Examples include aluminium hydroxide, calcium carbonate, magnesium carbonate, magnesium hydroxide, magnesium trisilicate and sodium bicarbonate.