Dr. Beth Corn on Everyday Health explains that antihistamines make people drowsy because the medication that penetrates the blood barrier treats the allergy and also affects the brain. In other words, the medication works against the histamine, a chemical produced by the central nervous system, as explained by Mayo Clinic. However, regular use of antihistamines makes them less likely to induce drowsiness because of a buildup of tolerance.Know More
Joseph Castro, a LiveScience Contributor, explains that histamines from the white blood cells and tissue cells seek out and attach themselves to cells that have histamine receptors when the immune system detects a potentially dangerous foreign substance. The histamines have an inflammatory response that dilates the blood vessels, which increases blood flow to the invasion site. This healing process has an effect on the immune system including regulating sleepiness and wakefulness. Castro notes that this disruption in the brain causes drowsiness.
According to WebMD, nighttime cold medicines include antihistamines, but other medications intended to work during the day do not contain antihistamines because of the potential for drowsiness to occur. Medicines such as Advil Cold and Sinus, Benadryl, Chlor-Trimeton, Comtrex Day/Night, Dimetane and Tavist often include drowsiness as a possible side effect.Learn more about Side Effects
The amount of time an antidepressant stays in the body depends on the medication. Some medications are 99 percent out of the body in around one day while others, such as Prozac, can take up to 25 days to leave the system.Full Answer >
To prevent niacin side effects, carefully follow dosage instructions, swallow extended-release capsules completely, take the medication with a meal and start by taking small doses initially, according to MedicineNet. Taking aspirin before taking a niacin dose may reduce itching and flushing, claims Jennifer Moll, PharmD, of About.com.Full Answer >
The medication Levothyroxine is known to cause both weight gain and weight loss, but it is more common for the medication to cause the patient to lose weight, according to the website Drugs. Taking normal doses of Levothyroxine should not cause weight loss, and it is not recommended to take the medication for weight loss because taking too much of it can be fatal.Full Answer >
The Harvard Medical School Family Health Guide explains that the expiration date stamped on a medication does not indicate that the medication is unsafe. In fact, many medications are still safe to use even 10 years after expiration, producing no additional effects.Full Answer >