Alka Seltzer XS Effervescent Tablets Alka-Seltzer XS Effervescent Tablets are a double action pain reliever for mild to moderate pain such as headache, migraine, back-ache (including lumbago), nerve pain (neuralgia & sciatica), period pain, toothache & sore throat. They also provide symptomatic relief from colds & influenza & from rheumatic pain (arthritis), muscle tenderness & stiffness (including fibrositis), muscular aches & pains, the pain of joint swelling & stiffness, strains & sprains. If you have a high temperature, Alka Seltzer XS Effervescent Tablets will effectively reduce this too. The main ingredients in Alka-Seltzer XS Effervescent Tablets are aspirin, which belongs to a group of medicines known as non-steroidal anti-inflammatory drugs (NSAIDs) & paracetamol. Aspirin & parcetamol both treat & pain & reduce fever, while aspirin is also an anti-inflammatory. They also contain caffeine which acts as a mild stimulant & sodium hydrogen carbonate & citric acid which help to create a sparkling solution.