Some side effects of L-tryptophan and valerian, two of the main ingredients in Alteril as listed on the official website of the sleep aid, may include heartburn, stomach ache and headache, according to WebMD. Side effects of the ingredient melatonin may include dizziness and daytime sleepiness, states Mayo Clinic.
L-tryptophan may cause stomach pain, heartburn, gas, belching and loss of appetite as well as nausea, vomiting and diarrhea, states WebMD. The substance may also cause sexual problems, blurred vision, lightheadedness and headache. More than 1,500 cases of eosinophilia-myalgia syndrome, a neurological condition that can cause long-term symptoms and even death, have been associated with the use of possibly contaminated L-tryptophan products. Side effects of valerian may include excitability, morning sluggishness, headache, insomnia and uneasiness. Although likely safe in medicinal amounts for short periods, valerian's safety during long-term use is unknown as of 2015.
Headaches, daytime sleepiness and dizziness are the most common side effects of melatonin, but the substance can also cause irritability, confusion, abdominal discomfort, mild anxiety and short-term depressive feelings, according to Mayo Clinic. Melatonin can interact with certain medications, such as birth control pills, drugs for diabetes, immunosuppressants and blood-thinning medications. The manufacturer advises against the use of Alteril by children, and pregnant women should not use the sleep aid without first consulting a doctor, as stated on Alteril.com.