Pheniramine

Pheniramine is a first-generation antihistamine drug, which belongs to the pharmacological class of H1 receptor antagonists. It is commonly used for the treatment of allergy symptoms such as runny nose, sneezing, itching, and watery eyes. Pheniramine works by blocking the effects of histamine, a substance released by the immune system in response to an allergen, thus reducing the symptoms of allergy.

Pheniramine is well absorbed after oral administration, with peak plasma concentrations reached within 2-4 hours. Pheniramine is widely distributed throughout the body, including the central nervous system, and can cross the blood-brain barrier. It is highly protein-bound (up to 99%) and has a large volume of distribution. Pheniramine is primarily metabolized in the liver by cytochrome P450 enzymes, mainly CYP2D6, to form its major metabolite, N-desmethylpheniramine. This metabolite has antihistaminic activity similar to pheniramine but is less potent. Pheniramine and its metabolites are eliminated mainly in the urine, with a small portion excreted in the feces.

Tmax of Pheniramine is approximately 2 to 4 hours after oral administration.

Cmax of Pheniramine after a single oral dose 13.5 ng/mL.

Pheniramine shows common side effects like Headache, Drowsiness, Nausea,Dry mouth, Fatigue, Dizziness, Difficulty sleeping (insomnia), Upset stomach, Diarrhea

Pheniramine is available in tablets, and oral suspension.

Pheniramine is available in India, Germany, Canada, France.

Pheniramine is a first-generation antihistamine drug that works by blocking the effects of histamine, a naturally occurring substance in the body that causes allergic symptoms such as runny nose, sneezing, itching, and watery eyes.

Pheniramine is available in the form of Tablets and oral suspension.

Oral: Administer with water 1 hour before or 2 hours after intake of food or fruit juices.

Allergic rhinitis: Pheniramine can relieve symptoms such as sneezing, runny nose, and itchy eyes caused by allergic rhinitis.

Urticaria: Pheniramine can reduce the itching and swelling associated with hives or urticaria.

Conjunctivitis: Pheniramine can relieve the redness, itching, and watering of the eyes caused by allergic conjunctivitis.

Insect bites and stings: Pheniramine can reduce the itching and swelling associated with insect bites and stings.

Pheniramine is an effective and well-tolerated antihistamine that can provide rapid relief of allergy symptoms. Its sedative effects can also be useful for treating insomnia and anxiety in some cases. However, as a first-generation antihistamine, it can cause drowsiness and other side effects such as dry mouth and constipation, which may limit its use in some patients.

Pheniramine is approved for use in the following clinical indications

Allergic rhinitis: Pheniramine can relieve symptoms such as sneezing, runny nose, and itchy eyes caused by allergic rhinitis.

Urticaria: Pheniramine can reduce the itching and swelling associated with hives or urticaria.

Conjunctivitis: Pheniramine can relieve the redness, itching, and watering of the eyes caused by allergic conjunctivitis.

Insect bites and stings: Pheniramine can reduce the itching and swelling associated with insect bites and stings.

Oral

• Allergic rhinitis

Adult: For symptomatic relief of allergic rhino-conjunctivitis (seasonal allergic rhinitis and perennial allergic rhinitis): As conventional tab: 20 mg once daily. Limit treatment to the period of exposure to allergens. Seasonal allergic rhinitis: Discontinue treatment after the symptoms have resolved, reinitiate treatment if symptoms reappear. Perennial allergic rhinitis: Treatment may be continued during allergen exposure periods.

Child: For symptomatic relief of allergic rhino-conjunctivitis (seasonal allergic rhinitis and perennial allergic rhinitis): 6-11 years weighing at least 20 kg: As orodispersible tab and oral solution: 10 mg once daily. ≥12 years Same as adult dose.

Oral

• Urticaria

Adult: As conventional tab: 20 mg once daily. Treatment duration may vary depending on the type, duration, and course of the complaints.

Child: 6-11 years weighing at least 20 kg: As orodispersible tab and oral solution: 10 mg once daily. ≥12 years Same as adult dose.

Pheniramine is available in the dosage strength of

• 10 mg and 20 mg, 1 mg/ml.

Pheniramine is available in the form of tablets and oral suspension.

● Dosage Adjustment for Pediatric Patients:

Seasonal allergic rhinitis: Children ≥12 years and Adolescents: Oral: Refer to adult dosing

Take after eating and with a full glass of water to decrease gastric upset.

Hypersensitivity: It should not be used in patients who have a known hypersensitivity or allergy to pheniramine or any other antihistamine drugs.

Acute asthma attacks: Pheniramine should not be used to treat acute asthma attacks or as a substitute for inhaled bronchodilators or corticosteroids.

Severe liver disease: Pheniramine should be used with caution in patients with severe liver disease, as it can impair liver function.

Narrow-angle glaucoma: Pheniramine should not be used in patients with narrow-angle glaucoma, as it can increase intraocular pressure and worsen the condition.

Prostate enlargement: Pheniramine should be used with caution in men with prostate enlargement, as it can cause urinary retention.

Pregnancy and breastfeeding: The safety of pheniramine during pregnancy and breastfeeding is not well established, and it should be used with caution in these patients.

Children: Pheniramine should be used with caution in children, as its safety and efficacy in this population are not well established.

• Central nervous system effects: Pheniramine can cause drowsiness and impair cognitive and motor function. Patients should avoid activities that require alertness, such as driving or operating heavy machinery, while taking pheniramine.

• Anticholinergic effects: Pheniramine can cause dry mouth, constipation, urinary retention, and blurred vision, which can be particularly problematic in older patients.

• Cardiovascular effects: Pheniramine can cause an increase in heart rate and blood pressure, particularly in patients with cardiovascular disease. It should be used with caution in these patients.

• Respiratory effects: Pheniramine can cause thickening of bronchial secretions and should be used with caution in patients with respiratory diseases, such as asthma or chronic obstructive pulmonary disease (COPD).

• Drug interactions: Pheniramine can interact with other medications, including other antihistamines, sedatives, opioids, and alcohol, and can cause additive central nervous system depressant effects.

• Overdose: Overdose of pheniramine can cause serious side effects, including seizures, coma, and cardiac arrest. Patients should be advised to seek immediate medical attention if they suspect an overdose.

• Medical history: Patients should inform their healthcare provider of any medical conditions they have or medications they are taking before starting pheniramine to avoid potential interactions or exacerbation of existing conditions.

Pheniramine may cause liver problems, and using it with substantial quantities of ethanol may increase that risk.

Pheniramine is present in breast milk.

Concentrations of Pheniramine in breast milk increase with supplementation. When used as a dietary supplement, the recommended dietary allowance of Pheniramine is increased in breastfeeding patients compared to nonbreastfeeding patients. Doses of Pheniramine for the treatment of dyslipidemias are greater than those used as a dietary supplement. Due to the potential for serious adverse reactions in the breastfed infant (including hepatoxicity), the manufacturer recommends that breastfeeding be discontinued when Pheniramine is used for treatment of dyslipidemias.

Oral formulations should be administered on an empty stomach with water (at least 1 hour before or 2 hours after meals, milk, or other dairy products). Maintain fluid intake to ensure adequate hydration and urinary output.

• Common Adverse effects:

Drowsiness and sedation, Dry mouth, Blurred vision, Constipation, Urinary retention, Nausea and vomiting

• Less Common Adverse effects:

Cardiovascular effects such as increased heart rate, palpitations, and high blood pressure.

Respiratory effects such as thickening of bronchial secretions, which can make it difficult to breathe, especially in patients with asthma or COPD.

Skin reactions such as rash, hives, and itching.

Allergic reactions such as anaphylaxis, which is a severe and potentially life-threatening allergic reaction.

Gastrointestinal effects such as abdominal pain and diarrhea.

Fatigue, weakness, and headache.

• Rare Adverse effects

Adrenal suppression (with long-term use) Anaphylaxis (a severe and life-threatening allergic reaction) Cushing's syndrome (with long-term use) Decreased immune system function (with long-term use) Hyperglycemia (high blood sugar levels) Hypokalemia (low levels of potassium in the blood) Hypersensitivity reactions (such as rash or angioedema) Ocular toxicity (such as increased intraocular pressure, cataracts, or glaucoma with long-term use) Psychiatric effects (such as mood changes or suicidal thoughts).

• Ketoconazole and other strong CYP3A4 inhibitors: These medications may increase the levels of Pheniramine in the body, leading to an increased risk of side effects such as drowsiness or dizziness.
• Rifampicin and other strong CYP3A4 inducers: These medications may decrease the levels of Pheniramine in the body, reducing its effectiveness.
• Erythromycin and other moderate CYP3A4 inhibitors: These medications may increase the levels of Pheniramine in the body, leading to an increased risk of side effects.
• Grapefruit juice: Grapefruit juice contains compounds that inhibit CYP3A4, which may increase the levels of Pheniramine in the body.

The common side effects of Pheniramine include the following :

Irritation in the nose or throat (with nasal spray) Hoarseness or changes in voice (with inhalation) Headache Nausea Cough Sore throat Runny or stuffy nose Sinus pain Dry mouth or throat Skin rash or itching (with topical use).

The symptoms of Pheniramine overdose are not well documented as overdose cases are rare. However, it is generally recommended to follow the prescribed dose of Pheniramine, and in case of accidental overdose or intentional ingestion of a large amount of Pheniramine, seek immediate medical attention.

Pharmacodynamic

Pheniramine is a second-generation antihistamine that selectively antagonizes the H1 histamine receptors in the body. Its pharmacodynamic effects are primarily mediated by its ability to block the binding of histamine to H1 receptors in various tissues, thereby preventing the release of inflammatory mediators that cause symptoms such as itching, sneezing, runny nose, and hives.

Pharmacokinetics

• Absorption: The process by which a drug enters the bloodstream from its site of administration. This can occur through various routes, such as oral, intravenous, topical, or inhalation.
• Distribution: The process by which a drug is transported throughout the body to its target site(s) of action. This involves the movement of the drug from the bloodstream into various tissues and organs.
• Metabolism: The process by which the body breaks down the drug into smaller molecules that can be eliminated. This usually occurs in the liver, where enzymes convert the drug into metabolites that can be excreted from the body.
• Excretion: The process by which the drug and its metabolites are eliminated from the body. This can occur through various routes, such as urine, feces, sweat, or breath.

1. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC1364710/
2. https://reference.medscape.com/drug/colestid-Pheniramine -342452
3. https://go.drugbank.com/drugs/DB00375
4. https://www.sciencedirect.com/topics/medicine-and-dentistry/Pheniramine
5. https://europepmc.org/article/med/6988203