Those using NyQuil should strictly follow the dosage chart or the physician's prescription. Overdose by increasing the amount of intake, taking it more often or extending the intake can cause serious side effects, such a... More » Health Medications & Vitamins

In 2011, Tylenol's parent company officially lowered the maximum dosage on its extra strength acetaminophen products to 3,000 milligrams from 4,000 milligrams per day, according to CBS News, and Tylenol's website include... More » Health Medications & Vitamins

The recommended dosage for adults and children over 12 is 30 milliliters every six hours for liquid Nyquil and two capsules with water every six hours for NyQuil LiquiCaps, according to Intake of either medica... More » Health Medications & Vitamins

The maker of NyQuil, Vicks, does not recommend using any of its products after the specified expiration date on the product's packaging. Vicks recommends that expired products are properly disposed of, and Vicks suggests... More »

The active ingredients in NyQuil are acetaminophen, dextromethorphan HBr and doxylamine succinate. NyQuil also contains a number of inactive ingredients. More »

Original formula NyQuil liquid cold and flu medicine contains 25 percent alcohol by volume, according to the State University of New York Potsdam. The percentage of alcohol is not listed on the label. Alcohol is the seco... More »

The ingredient in NyQuil that causes users to sleep is an antihistamine called doxylamine. The strong sedative power of antihistamines causes them to be used as active ingredients in many cold medicines and sleep aids, a... More »