Diphenhydramine

Diphenhydramine is an antihistamine, a class of medications that blocks the action of histamine, a neurotransmitter that causes allergic symptoms. It will relieve symptoms but will not speed recovery. Diphenhydramine is sold under the brand names Aler-Dryl, Allergia-C, Allermax, Altaryl, Banophen, Benadryl, Bromanate AF, Bydramine, Compoz Nighttime Sleep Aid, Dicopanol, Diphedryl, Diphen, Diphenadryl, Diphenhist, Diphenylin, Dytan, Hydramine, Nervine, Nytol, Pardryl, Q-Dryl, Siladryl, Sleepinal, Sominex, Twilite, and Unisom.

Uses
"Diphenhydramine is used to relieve red, irritated, itchy, watery eyes; sneezing; and runny nose caused by hay fever, allergies, or the common cold. Diphenhydramine is also used to relieve cough caused by minor throat or airway irritation. Diphenhydramine is also used to prevent and treat motion sickness, and to treat insomnia (difficulty falling asleep or staying asleep). Diphenhydramine is also used to control abnormal movements in people who have early stage parkinsonian syndrome (a disorder of the nervous system that causes difficulties with movement, muscle control, and balance) or who are experiencing movement problems as a side effect of a medication." Its labeled uses include: Allergic Conjunctivitis, Allergic Reactions, Allergic Rhinitis, Anaphylaxis, Cough, Dermatographic Urticaria, Extrapyramidal Disease, Idiopathic Parkinsonism, Insomnia, Motion Sickness, Nasal Congestion, Nausea, Nausea and Vomiting, Parkinsonism, Pruritus of Skin, Sneezing, Urticaria, Vertigo, and Vomiting.

Form, Route, and Dosage
Diphenhydramine is available as a tablet, a rapidly disintegrating (dissolving) tablet, a capsule, a liquid-filled capsule, a dissolving strip, and a liquid to take by mouth. Over-the-counter, diphenhydramine is available in the strength of 25mg. Patients over 12 years of age are instructed to take 1-2 tablets (25-50mg) every 4 to 6 hours, up to a maximum of 300mg in a 24 hour period. Children ages 6 to 12 are instructed to take only 1 tablet (25mg) every 4 to 6 hours. Diphenhydramine comes alone or in combination with other drugs, such as pain relievers, fever reducers, and decongestants.

Side Effects
Patients taking Diphenhydramine may experience side effects, including the following:
 * dry mouth, nose, and throat
 * drowsiness
 * dizziness
 * nausea
 * vomiting
 * loss of appetite
 * constipation
 * increased chest congestion
 * headache
 * muscle weakness
 * excitement (especially in children)
 * nervousness
 * vision problems
 * difficulty urinating or painful urination

As a Pollutant
Because humans and animals often do not fully metabolize pharmaceuticals in their body, they can excrete drugs or their breakdown products, which may the enter the environment.

In Sewage Sludge
Diphenhydramine has been found in sewage sludge. In the Targeted National Sewage Sludge Survey, a 2009 test of 84 samples of sewage sludge from around the U.S., the EPA found diphenhydramine in every samples in concentrations ranging from 36.7 to 5,730 parts per billion. There are no federal regulations governing how much of this drug may be present in sewage sludge applied to land as fertilizer.

Plant Uptake of Sludge Contaminants
Several pharmaceuticals are routinely found in sewage sludge and effluent from wastewater treatment plants, which are then used to fertilize or irrigate farm fields. A study by researchers at the University of Toledo simulated both fertilization with sewage sludge and irrigation with wastewater laced with three three pharmaceuticals, carbamazepine, diphenhydramine, and fluoxetine (Prozac), and two personal care products, triclosan and triclocarban, to then examine their uptake by soybean plants. The study found that, "With the exception of fluoxetine, all of the chemicals accumulated in the plant tissues from exposure to both wastewater and biosolids. The greatest accumulation was observed for carbamazepine, triclosan and tricloarban. Concentrations increased in the plant tissues up to six times the levels present in the biosolid amended soils. Greater accumulation of all chemicals was found in the soybeans exposed to soils treated with biosolids; however, this may be partially due to the naturally higher concentrations of these chemicals in the biosolids versus the wastewater."

Related SourceWatch articles

 * Biosolids
 * Sewage sludge
 * Food Rights Network
 * Pharmaceuticals

External resources

 * PubMed Health - Diphenhydramine
 * Diphenhydramine: MedlinePlus Drug Information