Unpacking the Pharmacy Shelf: What's Inside Your Sleep Aid?
Many people reach for an over-the-counter (OTC) sleep aid when they have trouble falling or staying asleep. While the variety of brands can be extensive, most of these products rely on a few key active ingredients to produce their sedating effects. The most prevalent ingredients fall into two main categories: antihistamines and dietary supplements. Understanding these ingredients, how they work, and their potential side effects is crucial for safe and effective use.
The Antihistamine Approach: Diphenhydramine and Doxylamine
The most common active ingredients in FDA-approved OTC sleep aids are first-generation antihistamines, specifically diphenhydramine and doxylamine succinate. You might recognize diphenhydramine as the active ingredient in Benadryl. These drugs are primarily designed to treat allergy symptoms, but their prominent side effect is drowsiness, which is why they are used in sleep medications.
How They Work: Histamine is a chemical your brain produces that helps you feel awake. First-generation antihistamines work by crossing the blood-brain barrier and blocking histamine receptors in the brain. This interference with histamine's role in the wakefulness cycle leads to a feeling of sedation or drowsiness.
- Diphenhydramine: Found in products like ZzzQuil, Unisom SleepGels, and Nytol, as well as combination pain-and-sleep products like Tylenol PM and Advil PM. It is typically taken about 30 minutes before bedtime.
- Doxylamine Succinate: This is the active ingredient in products like Unisom SleepTabs. It is considered one of the most sedating antihistamines available over-the-counter. A key difference is that doxylamine stays in the system longer than diphenhydramine, which may help with staying asleep but can also increase the likelihood of next-day grogginess. It is usually taken 30 minutes before bed.
Potential Side Effects and Risks of Antihistamine Sleep Aids
While effective for occasional sleeplessness, these medications are not recommended for regular or long-term use. Tolerance can develop quickly, meaning you may need higher amounts to get the same effect. Common side effects include dry mouth, blurred vision, constipation, and daytime drowsiness or a "hangover" effect. Use is particularly concerning for adults over 65, as it can increase the risk of confusion, dizziness, falls, and has been linked to an increased risk of dementia with long-term use. You should not take these products for more than two weeks without consulting a doctor.
Natural Supplements as Sleep Aids
Another category of sleep aids utilizes dietary supplements. The most well-known is melatonin.
- Melatonin: This is a hormone your body naturally produces to regulate your sleep-wake cycle. As daylight fades, your body's melatonin production increases, signaling that it's time to sleep. OTC melatonin supplements are a synthetic version of this hormone. Studies show it can be modestly effective, helping people fall asleep about nine minutes faster on average. It is often considered helpful for circadian rhythm disruptions like jet lag.
- Valerian Root & Other Herbals: Other supplements like valerian root, chamomile, and passionflower are also used for sleep. Valerian is thought to promote relaxation by influencing the neurotransmitter GABA. However, evidence for the effectiveness of many herbal supplements is often inconclusive, and since they are not regulated by the FDA, the contents and quality can vary.
Comparison of Common Sleep Aid Ingredients
| Ingredient | Type | How it Works | Common Brands | Key Consideration |
|---|---|---|---|---|
| Diphenhydramine | Antihistamine | Blocks histamine receptors in the brain to cause drowsiness. | ZzzQuil, Benadryl, Tylenol PM, Advil PM | Shorter acting, but tolerance can build quickly. |
| Doxylamine Succinate | Antihistamine | Blocks histamine receptors in the brain; highly sedating. | Unisom SleepTabs, Kirkland Sleep Aid | Longer lasting, may cause more next-day grogginess. |
| Melatonin | Dietary Supplement (Hormone) | Supplements the body's natural sleep-wake cycle hormone. | Various | Best for circadian rhythm issues like jet lag; not FDA regulated. |
| Valerian Root | Dietary Supplement (Herbal) | Thought to influence calming neurotransmitters like GABA. | Various | Evidence for effectiveness is mixed; not FDA regulated. |
Combination Products with Pain Relievers
It's important to be aware of combination products, especially if sleeplessness is accompanied by pain. Products like Tylenol PM, Advil PM, and Aleve PM combine a sleep aid (almost always diphenhydramine) with a pain reliever like acetaminophen, ibuprofen, or naproxen. While useful for pain-related sleeplessness, it's crucial not to take these if you don't have pain, to avoid consuming unnecessary medication.
Conclusion
The primary active ingredients in most over-the-counter nighttime sleep aids are the sedating antihistamines diphenhydramine and doxylamine. They work by blocking wakefulness signals in the brain and are intended for short-term, occasional use. Natural supplements like melatonin are also common alternatives that support the body's natural sleep processes. Due to potential side effects and risks, especially with long-term use and in older adults, it's essential to read labels carefully and consult with a healthcare provider to address persistent sleep problems.
For more information on sleep health, you can visit the Sleep Foundation.
