Alka-Seltzer Plus, produced by the Bayer Company, is sold as several different preparations; each is designed to relieve possible cold symptoms such as a fever, nasal congestion or cough. Alka-Seltzer Plus formulas may be used either during the day, when the patient needs to stay awake, or at night when the patient may need help falling asleep and staying asleep. The FDA recognizes all of the ingredients as safe. However, some of the compounds may cause side effects that can affect function. If a patient experiences any of these side effects, she should stop using the preparation and consult a doctor.
Side Effects of Aspirin
All Alka Seltzer Plus preparations contain aspirin to reduce fever. Aspirin may cause a number of side effects, including heartburn, stomach pain, nausea or vomiting. These symptoms are common, according to MedlinePlus, and a patient should consult a doctor if they do not subside after stopping the medicine. If vomitting with blood is present, or if stools appear black and tarry, the patient should discontinue the medicine and consult a doctor immediately.
Side Effects of Dextromethorphan
Dextromethorphan is found in Alka Seltzer preparations designed to help with coughs. It suppresses coughing by affecting a particular part of the brain. Side effects may include dizziness, drowsiness or lightheadedness, and occasionally gastric upset may occur. If a patient experiences a rash from this drug, MedlinePlus recommends seeing a doctor immediately.
Side Effects of Phenylephrine
Several types of Alka Seltzer Plus contain phenylephrine, a nasal decongestant that helps reduce sinus congestion and pressure by reducing the swelling of blood vessels. Phenylephrine is effective but it may also cause some side effects, such as nervousness, dizziness and agitation.
Side Effects of Doxylamine
Doxylamine is an anti-histamine present in Alka Seltzer Plus preparations that are used at night. It generally causes drowsiness and helps a patient to sleep. Doxylamine also produces several side-effects, including dryness of the mouth, nose and throat. It may also cause headache and increased chest congestion, according to MedlinePlus.
Side Effects of Chlorpheniramine
Chlorpheniramine is an anti-histamine similar to doxylamine. It is an ingredient in Alka-Seltzer formulas that relieve symptoms of the flu. Possible side effects are similar to those of doxylamine. However, it may also cause constipation or loss of appetite. Chlorpheniramine, like all anti-histamines, may lead to potentially serious side effects such as vision problems or difficulty urinating. These should be treated by a doctor immediately.