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Dextromethorphan vs Diphenhydramine
Introduction
For individuals suffering from common cold symptoms, such as coughing and sneezing, specific over-the-counter medications can be beneficial. Dextromethorphan and Diphenhydramine are two such drugs that may help manage these uncomfortable symptoms. Both work by affecting different receptors in the body but aim to bring relief to patients with colds or allergies. Dextromethorphan is a cough suppressant that affects the signals in the brain that trigger cough reflex, thus reducing the urge to cough. On the other hand, Diphenhydramine is an antihistamine primarily used for relieving allergy symptoms including itching, runny nose, and sneezing; it works by blocking histamines - chemicals in your body involved in immune responses to allergens.
Dextromethorphan vs Diphenhydramine Side By Side
| Attribute | Robitussin | Benadryl |
|---|---|---|
| Brand Name | Robitussin | Benadryl |
| Contraindications | Should not be taken with or have recently stopped using MAO inhibitors | Should not be taken with or have recently stopped using MAO inhibitors |
| Cost | $5-$8 for generic dextromethorphan | Approximately $18 for 48 capsules of ZzzQuil containing Diphenhydramine |
| Generic Name | Dextromethorphan | Diphenhydramine |
| Most Serious Side Effect | Severe dizziness or anxiety; feeling like you might pass out, hallucinations, severe nervousness or restlessness; hyperactivity leading to tremors | Signs of an allergic reaction such as hives; difficulty breathing; swelling in your face or throat, rapid heart rate or palpitations, tightness in the chest or trouble breathing |
| Severe Drug Interactions | MAO inhibitors | MAO inhibitors |
| Typical Dose | 15-30 mg every six to eight hours for adults | 25-50 mg orally every 4 to 6 hours |
What is Dextromethorphan?
Dextromethorphan (often found in over-the-counter cough suppressants like Robitussin) is a type of medication called an antitussive. It was first approved by the FDA in the 1950s and works as a cough suppressant, inhibiting signals to your brain that trigger the reflex to cough — effectively "trapping" them from reaching their destination. On the other hand, Diphenhydramine (more widely known as Benadryl), which was also approved for use by the FDA around the same time, belongs to another class of drugs called antihistamines. It's primarily used for treating symptoms of allergies such as sneezing, runny nose, itching or watering eyes but can also be effective against cold symptoms including cough due to its mild sedative effects. Unlike Dextromethorphan with its single target action on suppressing cough reflexes, Diphenhydramine acts more broadly across multiple targets thus potentially resulting in additional side effects such as drowsiness.
What conditions is Dextromethorphan approved to treat?
Dextromethorphan is approved for the treatment of various ailments:
- Temporary relief from coughs without phlegm that are caused by certain infections such as the common cold
- Minor throat and bronchial irritation
- Intense, nonproductive coughs
On the other hand, Diphenhydramine is an antihistamine used to relieve allergy symptoms such as watery eyes, runny nose, itching eyes/nose, sneezing, hives and itching. It can also be used to prevent and treat nausea, vomiting and dizziness caused by motion sickness.
How does Dextromethorphan help with these illnesses?
Dextromethorphan works to suppress coughs by affecting the signals in the brain that trigger the cough reflex. It does this by acting on sigma receptors and NMDA glutamatergic receptors within the central nervous system, thereby reducing the urge to cough. Dextromethorphan is a type of medication known as an antitussive and it is often used for temporary relief of coughs caused by minor throat and bronchial irritation.
On the other hand, Diphenhydramine primarily functions as an antihistamine which blocks histamine H1 receptors, thus alleviating allergy symptoms like sneezing, itching, watery eyes, and runny nose. Additionally, diphenhydramine also has sedative properties due to its ability to cross into the central nervous system where it inhibits neuronal firing. This characteristic makes it useful not only for treating allergies but also for aiding sleep or reducing motion sickness.
What is Diphenhydramine?
Diphenhydramine, known under many brand names such as Benadryl, is a first-generation antihistamine that works by blocking the effects of histamine in the body. It was initially approved by the FDA back in 1946. Diphenhydramine has powerful anticholinergic properties meaning it blocks another neurotransmitter, acetylcholine at muscarinic acetylcholine receptors. This lack of action on acetylcholine can lead to certain side effects like dry mouth and eyes, constipation and urinary retention - common side effects associated with medications having this property.
While Diphenhydramine is often used for its anti-allergy properties to treat symptoms such as runny nose or hives, it also has sedative properties which make it useful for treating insomnia or motion sickness. In contrast to dextromethorphan -- a medication primarily used for cough suppression – diphenhydramine may cause drowsiness which could be beneficial when sleep aid is needed but detrimental if alertness is required.
What conditions is Diphenhydramine approved to treat?
Diphenhydramine is a widely used antihistamine that has been approved for the treatment of:
- Allergic reactions, such as hay fever or skin allergies
- Insomnia and other sleep-related disorders
- Motion sickness, where it can also be used to prevent symptoms
- Certain symptoms of Parkinson's disease.
It's important to note that while Diphenhydramine does have mild sedative effects, it should not be used solely for its sedative properties unless advised by a medical professional.
How does Diphenhydramine help with these illnesses?
Histamine is a chemical involved in many functions of the body such as the immune and nervous system, and also plays a key role in allergic reactions. Diphenhydramine acts by blocking histamine H1 receptors thus inhibiting the action of histamines on these receptors which results in relief from allergy symptoms like runny nose, sneezing, watery eyes and itching. It also has effects on acetylcholine which can lead to drowsiness, making it an effective sleep aid unlike Dextromethorphan, which primarily targets cough suppression by acting on brain signals that trigger cough reflexes. Hence diphenhydramine might be prescribed when patients need help with both allergies and sleep troubles whereas Dextromethorphan will be more suitable for those dealing only with unproductive coughs.
How effective are both Dextromethorphan and Diphenhydramine?
Dextromethorphan and diphenhydramine both have long histories of use in treating symptoms of the common cold and flu, yet they function differently. Dextromethorphan is a cough suppressant that targets the part of the brain involved in triggering the coughing reflex, consequently providing relief from persistent coughing. On the other hand, diphenhydramine is an antihistamine widely used to relieve allergic reactions as well as cold symptoms.
The effectiveness of dextromethorphan and diphenhydramine was directly evaluated in a double-blind clinical trial which demonstrated similar efficacy profiles between these two medications when it comes to relieving cough caused by acute upper respiratory tract infections. However, due to its anticholinergic effects, patients taking diphenhydramine might experience side effects such as dry mouth or sleepiness more frequently than those taking dextromethorphan.
In terms of safety profile and tolerability among various populations including children and elderly patients, both drugs are generally considered safe when taken at recommended doses. However caution must be exercised with prolonged usage or overdose scenarios since they can lead to severe complications like hallucinations or heart problems.
While there's robust evidence supporting their stand-alone efficacies for addressing distinct sets of symptoms (cough suppression for dextromethorphan; allergy symptom relief for diphenhydramine), their combined use isn't typically recommended without professional medical advice due to potential additive sedative effects.
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At what dose is Dextromethorphan typically prescribed?
Oral dosages of Dextromethorphan range from 15-30 mg every six to eight hours for adults, but it has been seen that 15 mg can be sufficient to suppress a cough in most adults. Adolescents may start with a lower dosage at around 7.5-15 mg every six to eight hours. The dose may be increased if there is no response after several days, but the maximum dose should not exceed 120 mg/day in any case. On the other hand, Diphenhydramine's oral dosage ranges from 25–50 mg every four to six hours for adults and adolescents over the age of twelve. For children under twelve, doses are typically halved and should always be given based on professional medical advice.
At what dose is Diphenhydramine typically prescribed?
Diphenhydramine treatment typically begins at a dosage of 25-50 mg orally every 4 to 6 hours. The dose can then be increased if necessary, up to the maximum recommended dose of 300 mg/day, divided into multiple doses spaced 4 to 6 hours apart. If there is no response or insufficient response to treatment after a few days, it's advisable to consult with your healthcare professional. It should be noted that diphenhydramine may cause drowsiness and impair coordination; hence its use as an over-the-counter sleep aid. Therefore, caution must be used when driving or operating machinery while on this medication.
What are the most common side effects for Dextromethorphan?
Common side effects of dextromethorphan may include:
- Nausea, vomiting
- Dizziness, lightheadedness
- Drowsiness or sedation
- Confusion, anxiety or restlessness
- Slurred speech or difficulties in coordination
- Rash, itchy skin
On the other hand, diphenhydramine is associated with a different set of common side effects such as:
- Somnolence (sleepiness/drowsiness)
- Dry mouth and throat
- Blurred vision
- Constipation and upset stomach
-Dizziness and headache.
It's important to remember that each person may react differently to medication based on factors like their overall health condition, age, weight etc. Always consult your healthcare provider for advice tailored specifically to you.
Are there any potential serious side effects for Dextromethorphan?
Although Dextromethorphan is generally safe for use, in some rare cases it can cause serious side effects which include:
- Allergic reactions such as hives, difficulty breathing, and swelling of the face, lips or throat
- Severe dizziness or anxiety; feeling like you might pass out
- Slow heart rate, weak pulse, fainting or slow breathing (breathing may stop)
- Hallucinations (seeing things)
- Severe nervousness or restlessness; hyperactivity that leads to tremors
In extremely unusual situations, Diphenhydramine could result in problematic conditions. Watch out for:
- Blurred vision and dry eyes
- Difficulty urinating - this could be an indication of a severe reaction affecting your urinary system
- Fast pounding heartbeats -Increased pressure within the eye causing pain and potential vision problems
If any of these symptoms are experienced with either medicine it is essential to seek immediate medical attention.
What are the most common side effects for Diphenhydramine?
Diphenhydramine, commonly used for allergy relief and as a sleep aid, can cause certain side effects. These may include:
- Dry mouth, throat, and nose
- Dizziness or headache
- Loss of appetite
- Nausea or vomiting
- Constipation
- Difficulty urinating or an enlarged prostate
- Blurred vision
Additionally, Diphenhydramine could lead to more serious symptoms such as confusion or memory problems in older adults. It can also cause feelings of restlessness or excitability (especially in children), nervousness and insomnia. In some cases, it might lead to fast heartbeat and tremors. While less common, rash could occur too. Always consult your healthcare provider if these symptoms persist.
Are there any potential serious side effects for Diphenhydramine?
While Diphenhydramine is generally well-tolerated, some individuals may experience severe side effects. If you notice any of the following symptoms after taking diphenhydramine, seek immediate medical attention:
- Signs of an allergic reaction such as hives; difficulty breathing; swelling in your face or throat
- Rapid heart rate or palpitations
- Tightness in the chest or trouble breathing
- Painful urination or inability to urinate
- Confusion and feelings of restlessness or nervousness
- Uncontrolled movements (tremors), particularly in elderly users
Remember that these are not common occurrences but critical signs to look out for when using diphenhydramine.
Contraindications for Dextromethorphan and Diphenhydramine?
Both dextromethorphan and diphenhydramine, like most over-the-counter cough suppressants and antihistamines respectively, may cause drowsiness in some users. If you notice an increase in sleepiness or fatigue that hinders your daily activities, please consult with a healthcare professional.
Neither dextromethorphan nor diphenhydramine should be taken if you are currently taking or have recently stopped using monoamine oxidase (MAO) inhibitors. Always inform your physician about all the medications you are on; MAOIs will require a period of about two weeks to clear from your system to prevent potentially harmful interactions with both dextromethorphan and diphenhydramine.
How much do Dextromethorphan and Diphenhydramine cost?
For the brand name versions of these drugs:
- The price for 20 tablets of Benylin (containing Dextromethorphan, 15 mg per tablet) averages around $10, which works out to about $0.50 per day if you take it as advised.
- The price for a pack of ZzzQuil (containing Diphenhydramine, 25 mg per liquid cap) is approximately $18 for 48 capsules, working out to about $0.75/day.
Thus, if you are using the medication at recommended doses, then Benylin will generally be less expensive on a per-day treatment basis than ZzzQuil. Please note that cost should not be a primary consideration in determining which drug is right for your symptoms.
For generic versions of diphenhydramine and dextromethorphan:
-
Generic dextromethorphan can often be found in packages ranging from 20 to over-the-counter cough suppressants like Robitussin DM or Vicks DayQuil Cough & Congestion with approximate costs ranging from as low as $5-$8 making it roughly between $0.25 - $0.40/day.
-
Generic diphenhydramine is available in packs starting from around 100 capsules up to even larger quantities with strengths typically at either 25mg or 50mg/capsule depending on the manufacturer's offering; with prices generally starting around just under ten dollars and rising accordingly based upon quantity/brand chosen equating roughly between ~$0.10 - ~$1/day depending on specific dosage requirements/dosage frequency factors considered.
Popularity of Dextromethorphan and Diphenhydramine
Dextromethorphan, available in generic forms and under brand names such as Robitussin DM, was estimated to have been purchased by about 10 million people in the US for over-the-counter use in 2020. It is a common ingredient found in many cough suppressants and accounts for over 30% of non-prescription antitussives used by Americans. Dextromethorphan has maintained its popularity due to its effectiveness at reducing the frequency of coughing.
On the other hand, diphenhydramine is primarily known as an antihistamine but also exhibits strong sedative effects which contribute to its usage as a sleep aid. Inclusive of purchases both with and without prescription (such as Benadryl), it was used by approximately 5 million people in the USA during 2020. Diphenhydramine makes up around 15% of OTC sleep-aids purchases, highlighting its significant role within this market segment. The prevalence rate for diphenhydramine has remained relatively consistent throughout recent years.
Conclusion
Both dextromethorphan and diphenhydramine are well-established as over-the-counter medications for symptomatic relief of coughs and cold. Numerous clinical studies have demonstrated their effectiveness compared to placebo treatments. Dextromethorphan acts primarily as a cough suppressant, targeting the brain's cough center to decrease the urge to cough, while diphenhydramine is an antihistamine that relieves symptoms such as runny nose, sneezing, itchy eyes or throat by blocking histamines that trigger these reactions.
In some cases, both drugs may be used together in certain formulations designed for multi-symptom relief; however, this should be done under careful consideration due to potential side effects from each drug. Diphenhydramine can cause drowsiness and dry mouth while dextromethorphan may lead to mild nausea or dizziness.
Both drugs have generic versions available which provide considerable cost savings especially for those paying out of pocket. It's important to note that the full effect of these medications might not be immediately noticeable upon initial use.
Though generally well-tolerated by most people with few side effects, patients must pay attention when starting treatment and seek medical help if they notice any severe adverse reactions like difficulty breathing or swelling in face/lips/tongue/throat.
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Refrences
- Konturek, S. J., Tasler, J., Cieszkowski, M., Szewczyk, K., & Kromer, W. (1989). Comparison of Telenzepine, Pirenzepine and Atropine on Gastric Acid and Pepsin Secretion in Response to Histamine, Pentagastrin, Bethanechol, Sham-Feeding and Feeding. Digestion. S. Karger AG.http://doi.org/10.1159/000199894
- Gelotte, C. K., Zimmerman, B. A., & Thompson, G. A. (2017, October 2). Single‐Dose Pharmacokinetic Study of Diphenhydramine HCl in Children and Adolescents. Clinical Pharmacology in Drug Development. Wiley.http://doi.org/10.1002/cpdd.391