Adults and children 12 years of age and older may take 30 milliliters of NyQuil Cold & Flu liquid every six hours, not to exceed four doses in 24 hours, states Vicks, the medicine's manufacturer. Individuals should only measure doses using the dose cup provided in the package.
Children from age 4 to under 12 years should only take NyQuil if directed by a doctor. Children under the age of 4 years should not take Nyquil, according to Vicks. NyQuil contains a pain reliever, a cough suppressant and an antihistamine. This combination of medicines relieves many cold symptoms, including headache, fever, runny nose, cough and sore throat.