Diphenhydramine vs Chlorpheniramine

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For individuals suffering from allergic reactions or symptoms such as runny nose, sneezing, and itching, certain antihistamine drugs that inhibit the action of histamine can help in alleviating discomfort and managing symptoms. Diphenhydramine and Chlorpheniramine are two such drugs often recommended for allergies. They each block different histamine receptors but both provide relief to allergy sufferers. Diphenhydramine is a first-generation antihistamine that crosses the blood-brain barrier and may cause more drowsiness than second-generation antihistamines like Loratadine. On the other hand, Chlorpheniramine also belongs to the group of first-generation antihistamines but it's less sedating compared to diphenhydramine because its structure allows for less penetration into the central nervous system.

What is Diphenhydramine?

Diphenhydramine (the generic name for Benadryl) was among the first antihistamines developed to combat allergy symptoms and has been available since 1946. It works by blocking histamine, a substance your body produces during an allergic reaction, thereby reducing or eliminating the associated symptoms. However, it also readily crosses the blood-brain barrier causing drowsiness - a side effect often utilized in over-the-counter sleep aids.

On the other hand, Chlorpheniramine is another early generation antihistamine but has less of a sedating effect compared to Diphenhydramine. It likewise blocks histamine response but does not cross into the brain as easily as Diphenhydramine does. This results in fewer instances of drowsiness making it more favorable for those needing to remain alert while dealing with allergies.

Both drugs are effective in treating allergy symptoms such as runny nose, sneezing and itching though individual responses can vary significantly due to personal tolerance and sensitivity.

What conditions is Diphenhydramine approved to treat?

Diphenhydramine is approved for the treatment of different types of conditions:

  • Allergy symptoms, like hay fever or other upper respiratory allergies
  • Itching and pain caused by hives and rashes
  • Insomnia (as it has sedative properties)
  • Motion sickness prevention Chlorpheniramine operates similarly but does not have approval as a sleep aid.

How does Diphenhydramine help with these illnesses?

Diphenhydramine works to alleviate symptoms of allergies and colds by blocking the action of histamine, a chemical in the body that causes many common allergy symptoms. It does this by preventing it from binding to its receptors on cells, which keeps levels controlled for longer periods. Histamine is an organic compound involved in local immune responses as well as regulating physiological functions in the gut and acting as a neurotransmitter for the brain, spinal cord, and uterus. It plays important roles in various allergic reactions when released during these instances. Individuals with allergies have hypersensitive immune responses leading to higher levels of histamine release. Therefore, diphenhydramine can limit the negative effects of this overreaction by increasing control over histamine activity helping patients manage their condition and stabilize their physical state.

Chlorpheniramine also has antihistaminic properties that help combat allergy symptoms but unlike Diphenhydramine it's less likely to cause drowsiness making it more suitable medication for those who need relief from allergic reactions but want to maintain regular daily activities without feeling sleepy or fatigued.

What is Chlorpheniramine?

Chlorpheniramine is an antihistamine medication that's a part of the alkylamine class, which means it works by blocking the effect of histamines in your body. Histamines are chemicals responsible for many allergy symptoms. Chlorpheniramine was first approved by the FDA in 1948 and has been helping people manage their allergies ever since.

Unlike diphenhydramine, chlorpheniramine doesn't cross into the brain as readily and therefore does not typically cause drowsiness, a common side effect associated with other antihistamines like diphenhydramine. This makes it potentially more suitable for daytime use or for people who need to maintain alertness but require relief from allergic symptoms such as sneezing, itching, runny nose or watery eyes. It should be noted however that non-drowsy does not mean no-drowsiness; some users may still experience this side-effect.

It can be beneficial particularly for individuals who do not respond well to other typical antihistamines such as Diphenhydramine.

What conditions is Chlorpheniramine approved to treat?

Chlorpheniramine is a trusted, FDA-approved antihistamine that's been used for many years to treat:

  • Allergic rhinitis (hay fever)
  • Urticaria (hives)
  • Other symptoms of upper respiratory allergies or the common cold, such as sneezing, itching, watery eyes, and runny nose.

How does Chlorpheniramine help with these illnesses?

Histamine is an organic compound involved in local immune responses and regulating physiological function in the gut. It also serves as a neurotransmitter, communicating between brain cells. High levels of histamine can contribute to symptoms such as sneezing, itching, watery eyes, or a runny nose - all typical signs of an allergic reaction.

Chlorpheniramine operates by blocking the effects of histamine in your body, thereby mitigating these uncomfortable allergy symptoms. As an antihistamine, Chlorpheniramine binds to H1 receptors throughout the body preventing histamines from triggering allergic reactions. Although diphenhydramine works on similar principles to alleviate allergies, chlorpheniramine is often preferred for its less sedative side-effects. Like other first-generation antihistamines though, it may still cause some drowsiness compared to newer generation medications but perhaps not as much as with diphenhydramine.

How effective are both Diphenhydramine and Chlorpheniramine?

Both diphenhydramine and chlorpheniramine are first-generation antihistamines with a long history of providing effective relief from allergy symptoms; they were both introduced in the mid-20th century. Since they act on the same histamine receptors, their use may be determined by individual patient responses or specific side effect profiles.

In a 1976 clinical trial, diphenhydramine and chlorpheniramine showed similar efficacy in managing symptoms such as sneezing, itching, watery eyes, and runny nose. Despite this similarity in effectiveness, it's important to note some differences between these two medications: Chlorpheniramine tends to cause less drowsiness than diphenhydramine – a common side effect associated with first-generation antihistamines.

An analysis of multiple studies published up until 2002 confirmed that while both drugs effectively alleviate allergy symptoms within the first few hours of treatment, their side effects differ notably. Diphenhydramine is more likely to cause drowsiness compared to many other antihistamines - including chlorpheniramine - but can also provide temporary relief for insomnia when used at night because of its sedative properties.

A review conducted in 2011 suggested that despite being older medicines compared to second-generation antihistamines like loratadine or fexofenadine, diphenhydramine and chlorpheniramine remain popular choices due primarily to their affordability. However, given their potential for causing drowsiness (particularly with diphenhydramine), they're generally recommended for evening use or situations where potential sedation won't interfere significantly with one’s daily activities.

abstract image of a researcher studying a bottle of drug.

At what dose is Diphenhydramine typically prescribed?

Oral dosages of Diphenhydramine range from 25-50 mg every 4 to 6 hours for adults and children over the age of 12. For children aged 6 to under 12, the dosage is typically halved at approximately 12.5 -25 mg every four to six hours. On the other hand, Chlorpheniramine has a typical oral dosage of up to four times per day with intervals not less than four hours in between doses; an adult or child over twelve years old should take no more than one tablet (4mg) whereas children ages six through eleven should take half a tablet (2mg). It's important that these guidelines are followed strictly and any increase in dose or frequency must be directed by a health professional as exceeding recommended dosages can lead to serious side effects.

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At what dose is Chlorpheniramine typically prescribed?

Chlorpheniramine treatment is usually initiated at a dosage of 4 mg every 4 to 6 hours. The dose can then be increased up to a maximum of 24 mg/day, divided into four or six doses and spaced evenly throughout the day. If there's no response to the initial dosage after several days, your doctor may decide to increase your daily dose gradually. It's important not to exceed the recommended maximum dosage of Chlorpheniramine as it could lead to serious side effects such as severe drowsiness, confusion, weakness or difficulty urinating. Always consult with a healthcare provider before adjusting any medication dosages.

What are the most common side effects for Diphenhydramine?

Common side effects of Diphenhydramine may include:

  • Drowsiness, dizziness
  • Constipation
  • Stomach upset
  • Dry mouth/nose/throat
  • Thick nasal discharge
  • Headache
  • Nervousness

On the other hand, Chlorpheniramine may cause:

-Drowsiness or sleepiness/drowsiness (most common) -Dry eyes and blurred vision, -Nausea or vomiting. -Urinary retention, -Dry mouth, -Upset stomach, -Chest congestion.

As a note, both medications can intensify symptoms if combined with alcohol. Always consult your healthcare provider to understand any potential reactions or interactions.

abstract image of a patient experiencing side effect

Are there any potential serious side effects for Diphenhydramine?

While Diphenhydramine and Chlorpheniramine are both antihistamines used to relieve symptoms of allergies, colds, and the flu, they may have different side effects. For instance:

  • An allergic reaction to either drug could cause hives; difficulty breathing; swelling of your face, lips, tongue or throat.
  • Overdose symptoms might include severe drowsiness, nausea, dry mouth or nose/throat irritation
  • Vision changes such as blurred vision which may lead to serious eye pain/swelling/redness
  • Mental/mood changes (such as restlessness or confusion), shaking (tremor), trouble urinating or weak/rapid pulse rate in some cases
  • Dry mouth/nose/throat leading to excessive thirst Severe dizziness/drowsiness that could potentially make you pass out

In very rare instances these medications can also result in serotonin syndrome. Symptoms can range from agitation and hallucinations to fever and muscle stiffness/twitching among others. If any of these symptoms occur after taking either medication then immediate medical assistance should be sought.

What are the most common side effects for Chlorpheniramine?

Chlorpheniramine, commonly used to relieve allergy symptoms, can lead to a variety of side effects including:

  • Dry mouth and throat
  • Blurred vision
  • Upset stomach or constipation
  • Drowsiness or dizziness
  • Difficulty in urination
  • Nervousness or restlessness

Less common but more serious side effects could include confusion, fast heart rate, rash or difficulty breathing. These are not all the possible side effects and individual response may vary. It's also worth noting that Chlorpheniramine might cause less drowsiness compared to Diphenhydramine.

Are there any potential serious side effects for Chlorpheniramine?

While Chlorpheniramine is generally considered safe, it can cause severe side effects in certain circumstances. Be sure to watch out for:

  • Signs of an allergic reaction such as hives, difficulty breathing, swelling in your face or throat
  • Severe dizziness or nervousness
  • Little or no urination
  • Fast or irregular heartbeats
  • Easy bruising or bleeding (nosebleeds, bleeding gums)
  • A seizure (convulsions)
  • Unusual thoughts or behavior; confusion, hallucinations; extreme fear

If you experience any of these symptoms after taking chlorpheniramine, seek immediate medical attention. These could be signs of a serious condition that requires prompt treatment.

Contraindications for Diphenhydramine and Chlorpheniramine?

Both diphenhydramine and chlorpheniramine, like most other antihistamines, may exacerbate symptoms in some people. If you notice any severe allergic reactions or side effects such as difficulty breathing or swelling of the face, tongue, or throat after taking these medications, please seek immediate medical attention.

Neither diphenhydramine nor chlorpheniramine should be taken if you are consuming alcohol or using sleep aids. These substances can intensify drowsiness caused by antihistamines and lead to serious negative consequences. Always inform your healthcare provider about all the medications and supplements you are currently taking; certain drugs may interact negatively with diphenhydramine and chlorpheniramine.

Also note that both of these medicines should not be used without doctor's advice for children under six years due to potential risks associated with child health.

How much do Diphenhydramine and Chlorpheniramine cost?

The cost of brand name versions for these medications are as follows:

  • The price of 100 tablets of Benadryl (brand name version of Diphenhydramine, 25 mg) averages around $7 to $10. Depending on your dose, it works out to approximately $0.07-$0.20 per day.
  • The price for a bottle containing 24 tablets of Chlor-Trimeton (the brand name version of Chlorpheniramine, 4mg each) is about $5 to $8. This works out roughly to be between $0.21 and $0.33 per day.

Thus, if you take the same dosage for both drugs daily, the generic diphenhydramine would work out cheaper than the chlorpheniramine on a per-day basis.

For their generic versions:

  • Generic diphenhydramine is available in packs ranging from 25 up to hundreds with costs starting from as low as about one cent per tablet or even less if purchasing larger quantities.

  • Similarly, generic chlorpheniramine can also be found in various pack sizes and prices start at just over one cent per tablet when bought in bulk.

Again note that while cost comparisons are important for some consumers, deciding which antihistamine medication best suits your needs should mainly depend upon its effectiveness against your specific symptoms and how well you tolerate any potential side effects rather than only considering how much it costs.

Popularity of Diphenhydramine and Chlorpheniramine

Diphenhydramine, available both in generic form and under brand names such as Benadryl, was estimated to have been used by approximately 10 million people in the US in 2020. Diphenhydramine accounted for roughly 18% of over-the-counter (OTC) antihistamine purchases in the country. However, it appears to be one of the most commonly used first-generation antihistamines (which are known to cause drowsiness). The use of diphenhydramine has remained steady over the past decade.

Chlorpheniramine, including brand versions such as Chlor-Trimeton, had a slightly lower usage rate with about 7 million users recorded for that same year within the USA. In terms of OTC antihistamine sales numbers, chlorpheniramine represented around 12%. This medication also falls into the category of first-generation antihistamines but is often preferred due to its less sedative effects compared to diphenhydramine. Similar to diphenhydramine though, chlorpheniramine's prevalence has not seen any significant changes over the last decade.


Both Diphenhydramine and Chlorpheniramine are antihistamines commonly used to treat symptoms of allergies and the common cold, such as runny nose, sneezing, itching and watery eyes. They work by blocking histamine receptors in the body which prevents allergic reactions from occurring. Both medications have a long history of use and are backed by numerous clinical studies indicating their effectiveness.

In some instances, these drugs may be utilized together under careful consideration by a healthcare professional due to differences in duration of action; diphenhydramine tends to have a shorter duration but is more potent than chlorpheniramine.

Diphenhydramine can also induce sleepiness making it useful for those suffering from insomnia or needing help with sleep while experiencing allergy symptoms. On the other hand, chlorpheniramine has less sedative effect and may be preferred for daytime use when drowsiness would be detrimental.

Both medicines are available in generic form representing significant cost savings especially for patients who must pay out-of-pocket. The onset of relief might not always be instant; an adjustment period could occur where effects become more noticeable over time.

Though generally well-tolerated, side effects like dry mouth, constipation, blurred vision or drowsiness can occur with both drugs. As with any medication regimen changes or new symptoms should prompt consultation with a healthcare professional.