* Doxylamine succinate is the sedating ingredient of NyQuil and Syndol * In Commonwealth countries, such as Australia, Canada, South Africa and the United Kingdom, doxylamine is available prepared with paracetamol (acetaminophen) and codeine under the brand name Dolased, Syndol, or Mersyndol, as treatment for tension headache and other types of pain. * Doxylamine succinate is used in general over-