DOXYLAMINE 

What is doxylamine?

In contrast with other antihistamines typically used for allergy symptoms, doxylamine is a first-generation antihistamine commonly used as a short-term treatment for insomnia. However, it can also be used for allergy symptoms such as nasal congestion, sneezing, runny nose, and itchy nose, as well as nausea and vomiting in pregnancy (when combined with pyridoxine or vitamin B6). For adults or children ages 12 and older, it can be taken as 25-50 mg at bedtime as needed for insomnia.

How can doxylamine help alleviate certain long COVID symptoms? 

Sleep-related disturbances are common after COVID and may be present in up to 52% of long COVID patients.¹ Insomnia can also contribute to downstream effects such as metabolic and cardiovascular diseases, immune responses, and increased depression and anxiety. While non-pharmacological measures for treating insomnia are preferred, such as maintaining good sleep habits, maximizing exposure to natural daylight, especially in the morning, and following a night routine, pharmacological measures such as doxylamine can improve sleep.

Doxylamine can also be an active ingredient in Nyquil, along with dextromethorphan and acetaminophen (Tylenol). Nyquil helps reduce cough, nasal congestion, a runny nose, and insomnia, but it should not be solely taken to fall asleep. When taken in excess, it can also cause more serious side effects, such as dizziness, dry mouth, headaches, and the potential for liver damage if taken with other acetaminophen-containing products.

What evidence supports doxylamine’s use for long COVID?

There is currently a lack of studies assessing the use of doxylamine for long COVID. Prescription medications used to treat insomnia include benzodiazepines, which are not preferred for long-term use and have a risk of abuse and dependence when used chronically. Thus, doxylamine may be a safer alternative available over-the-counter that can be used to treat short-term insomnia in long COVID patients.

What are some things to watch out for with doxylamine?

Doxylamine should not be taken longer than two consecutive weeks, as it can become less effective. Patients can also build up a tolerance to the medication, so it should not be taken regularly.² 

Due to its sedative effects, doxylamine should not be taken during the day before driving or operating heavy machinery. It should not be taken with alcohol or a drug class called monoamine oxidase inhibitors (MAOIs) and should be used with caution when taking other drugs that depress the central nervous system (CNS).

Doxylamine can also cause constipation, urinary retention, and blurred vision, especially when taken with certain other medications. If you are taking this medication more frequently, you should let your doctor know, as it can contribute to the side effects of other medications. Doxylamine is meant as a short-term treatment for insomnia and should not be taken chronically, particularly in older adults. It should also be used with caution in patients with narrow-angle glaucoma, urinary obstruction or gastrointestinal obstruction, and peptic ulcers.

References:

1)      Guezguez F, Romdhani M, Boutaleb-Joutei A, Chamari K, Ben Saad H. Management of long-COVID-19 patients with sleep disorders: practical advice to general practitioners. Libyan J Med. 2023 Dec;18(1):2182704. doi: 10.1080/19932820.2023.2182704

2)      Pacheco D and Rehman Anis. Does Nyquil make you sleepy? Sleep Foundation. May 4, 2023. Accessed November 13, 2023. https://www.sleepfoundation.org/sleep-aids/does-nyquil-make-you-sleepy#:~:text=fully%20worn%20off.-,Should%20You%20Take%20Nyquil%20for%20Sleep%3F,for%20more%20than%20two%20weeks.