Last reviewed by Editorial Team on September 5th, 2018.
Is diphenhydramine safe during pregnancy
Benadryl is a Brand name for antihistamine drug that contains diphenhydramine as an active ingredient. This substance reduces the effects of natural histamine during allergic reaction in the body.
Benadril’s products can also contain acetaminophen that is used as a pain reliever and fever reducer and phenylephrine used as a nasal decongestant.
Products for UK market contain different antihistamines as an active ingredient instead of diphenhydramine, such as Benadryl Allergy Relief containing the antihistamine acrivastine and Benadryl One a Day Relief containing the long acting antihistamine cetirizine.
Benadryl is available for oral and topical use. Benadryl is used for relieving the symptoms of allergy, hay fever and the common cold such as: itching, ash, runny nose, sneezing, watery eyes, itchy eyes, nose or throat, and cough.
It can be also used for the prevention and treatment of nausea, vomiting and dizziness that can be caused by motion sickness. Diphenhydramine also has hypnotic effects and it can help to relax and fall asleep.
This drug can also be used alone or in combination with other medications for the treatment of tremor and muscle stiffness caused by Parkinson’s disease. Certain side effects of psychiatric drugs such as involuntary movements and muscle stiffness can also be treated with this medication.
There are many products on the market containing diphenhydramine such as: Benadryl Allergy Dye-Free LiquiGels, Children’s Triaminic Thin Strips Allergy, Children’s Benadryl Allergy, Alka-Seltzer Plus Allergy, PediaCare Children’s Allergy, Nytol, Simply Sleep, Sominex, QlearQuil Nighttime Allergy Relief, Unisom SleepGels, Unisom SleepMelts, Tranquil Nighttime Sleep Aid, ZzzQuil, Benadryl One a Day Relief and Benadryl Allergy Relief.
How Benadryl works in the body
Diphenhydramine is first-generation antihistamine with anticholinergic, antiemetic, sedative and antitussive properties. It is histamine – H1 receptor antagonist. Diphenhydramine can reduce the intensity of allergic symptoms, by reducing the effects of histamine on the capillaries.
This drug crosses the blood–brain barrier in the CNS, where also antagonizes H1 receptors, causing sedation, relaxation and drowsiness. Diphenhydramine is also a potent competitive antagonist of muscarinic acetylcholine receptors.
In high doses it can cause anticholinergic syndrome. This anticholinergic property is used for the treatment of Parkinson’s disease. Diphenhydramine can also act as a sodium channel blocker in cells, so it can be also used as a local anesthetic.
It has been shown that diphenhydramine can inhibit the reuptake of serotonin. Studies on rats showed that this drug is a good potentiator of analgesia induced by morphine, however this is not the case for endogenous opioids.
Acetaminophen is highly selective COX-2 inhibitor that inhibits prostaglandin synthesis. It can inhibit COX-2 in CNS. Acetaminophen also acts on the hypothalamic heat regulating centers to produce antipyresis.
Acetaminophen’s reactive metabolite N-acetyl-p-benzoquinone imine (NAPQI) can cause a potentially fatal, hepatic necrosis through the process of lipid peroxidation if acetaminophen is overdosed (more than 4g daily).
Phenylephrine is sympathomimetic with direct action on the adrenergic receptor system. The vasoconstriction is produced after α-adrenergic receptors activation.
Acrivastine is a second generation antihistamine that works as an antagonist of histamine H1-receptor.
Cetirizine is also a second generation antihistamine that works as an antagonist of histamine H1-receptor. Unlike many other antihistamines, cetirizine doesn’t have anticholinergic properties
Can you take Benadryl during pregnancy
It is not recommendable to use Benadryl during pregnancy without consulting doctor. Diphenhydramine is recommended for administration during pregnancy only when benefits outweigh risks.
Benadryl is usually considered to be safe during pregnancy and it is commonly used as a sedative antihistamine for treating minor flu and cold symptoms such as watery eyes, stuffy nose, congestion, sneezing and nausea as well as allergy symptoms like rashes, itching and hives. It can be also used for the treatment of minor anxiety and as a sleep aid in pregnancy.
The FDA has established 5 categories to indicate the potential risk of a drug to cause birth defects if it is used during pregnancy. The categories are determined by the risk to benefit ratio and reliability of documentation.
Benadryl is in FDA pregnancy category B, which means that diphenhydramine does cross the placenta but the studies on animals have shown no adverse effects on the fetus; however, there is a lack of controlled studies on human pregnancy.
Drowsiness is the most common and can be very harmless side effect of this medicine in pregnancy.
Some case reports studies have shown possible association between diphenhydramine administration during first trimester and an increased risk cleft palate or lip (opening in the upper lip or roof of the mouth that may extend into the nose) in newborns.
One case study showed oxytocin-like side effects of the drug during pregnancy when diphenhydramine was overdosed. These side effects were occurred less in non-pregnant patients compared to pregnant patients.
Another case study has found that daily use of 150 mg Benadryl during pregnancy can led to withdrawal symptoms in the baby. Infant have developed tremor on the fifth day of life which was treated with phenobarbital.
One study found that using Benadryl together with Restoril (temazepam) can significantly increase the risk of fetal morbidity.
Topical administration of Benadryl is considered to be safe in pregnancy and there is little evidence that fetus can be harmed. However, there are no adequate data, regarding whether the diphenhydramine in the ointment formulation can cross through the placenta.
Occasional usage of Benadryl during pregnancy has not been associated with any serious adverse effects in the nursing baby. But, prolonged Benadryl administration is contraindicated because the drug can be excreted in the breast milk when it is taken by breastfeeding women.
Studies have shown that larger doses and long term use of diphenydramine can decrease the breast milk supply and can have negative effects on the infants such as irritability and lethargy.
How many Benadryl can patients take during pregnancy
It is usually recommended 25mg to 50mg orally, on every six hours in the first trimester, while the dosage should not go above 25mg in six hours during the last two trimesters.
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