to <4 grams (4,000 mg) daily in adults or <2.6g (2,600 mg) daily in children <12 years of age to reduce the risk of liver damage. Products containing dextromethorphan Those prescribed monoamine oxidase inhibitor (MAO-i) should avoid the use of DayQuil products containing dextromethorphan within 2 weeks to avoid risks of Serotonin Syndrome. References External links Vicks.com Vicks brands Products introduced in 1974