Restavit helps relieve insomnia. It is intended for short term use to re-establish regular sleep patterns. Do not use it for more than ten days consecutively. Insomnia is having trouble getting to sleep or staying asleep. It may also be the feeling that you are not getting enough sleep. Restavit belongs to a group of medicines called antihistamines. They block the action of histamine and other substances produced by the body to provide relief from allergic symptoms. Some antihistamines, including doxylamine cause the central nervous system to slow down at the same time and this provides relief for insomnia.