phenindamine

Action and Spectrum

Actions and spectrum: 

Action: 

phenindamine works by blocking or inhibiting the action of histamine at H1 histamine receptors. Histamine is the chemical released by cells in response to allergens, leading to symptoms such as itching, sneezing, runny nose, and watery eyes. 

• By blocking the effects of histamine, phenindamine helps alleviate these allergy symptoms and provides relief to individuals with allergic reactions. 

Spectrum of Use: 

phenindamine is used to treat a range of allergic conditions, including: 

• Allergic rhinitis: This includes symptoms like sneezing, runny or stuffy nose, and itching caused by airborne allergens like pollen, dust mites, & pet dander. 
• Allergic conjunctivitis: phenindamine can relieve itchy, red, and watery eyes associated with allergic reactions. 
• Urticaria (hives): It can help reduce itching and skin rashes caused by allergic hives. 
• Pruritus (itching): phenindamine may also be used to alleviate generalized itching due to allergies or other causes. 

Drug Interaction

Adverse Reaction

Frequency not defined 

Drowsiness 

headache 

stomach upset 

irritability 

Dizziness 

loss of appetite 

visual disturbances 

dry mouth 

Black Box Warning

Black Box Warning: 

There is no specific black box warning associated with phenindamine. 

Contraindication / Caution

Contraindication/Caution: 

Contraindication: 

• Hypersensitivity: phenindamine should not be used in individuals who have a known hypersensitivity or allergy to phenindamine or other antihistamines. 
• Nursing Mothers: phenindamine is not recommended in breastfeeding women due to the potential of the drug passing into breast milk and affecting the nursing infant. 
• Glaucoma: phenindamine should be used with caution or avoided in individuals with narrow-angle glaucoma, a condition that can be exacerbated by the anticholinergic effects of the medication. 
• Lower Respiratory Conditions: Individuals with conditions such as asthma, COPD, or other lower respiratory conditions may need to exercise caution when using phenindamine due to its potential to thicken respiratory secretions. 
• Bladder Neck Obstruction: phenindamine should be used with caution in individuals with bladder neck obstruction or other conditions that may be worsened by the anticholinergic effects of the drug. 
• Gastrointestinal Obstruction: phenindamine should be used cautiously in individuals with gastrointestinal obstruction due to its potential to slow down gastrointestinal motility. 

Caution: 

• Central Nervous System (CNS) Effects: phenindamine and other antihistamines can cause drowsiness, sedation, and impairment of mental alertness.  
• Alcohol and Other Depressants: Alcohol and other substances that depress CNS can enhance the sedative effects of phenindamine. Therefore, caution should be exercised when consuming alcohol or taking other medications with sedative properties while using phenindamine. 
• Elderly Individuals: Elderly individuals may be more susceptible to the CNS depressant effects of phenindamine. They should use the medication with caution and under the guidance of a healthcare professional. 
• Cardiovascular Conditions: phenindamine can have anticholinergic effects, which may impact heart rate and blood pressure.  
• Urinary Retention: phenindamine’s anticholinergic effects can lead to urinary retention, particularly in individuals with underlying urinary conditions. Caution should be exercised in such cases. 
• Thyroid Conditions: phenindamine can interfere with thyroid function tests, potentially leading to inaccurate results. Inform healthcare providers if you are taking phenindamine before undergoing thyroid function testing. 
• Pregnancy: The safety of phenindamine during pregnancy has not been well established. Pregnant individuals should consult their healthcare provider before using phenindamine. 
• Breastfeeding: phenindamine may pass into breast milk and affect the nursing infant. It is not recommended for breastfeeding individuals.

Comorbidities: 

• Cardiovascular Conditions: phenindamine has anticholinergic properties that can impact heart rate and blood pressure. Individuals with cardiovascular conditions such as hypertension, arrhythmias, or a history of heart disease should use phenindamine cautiously and under the guidance of a healthcare professional. 
• Glaucoma: phenindamine’s anticholinergic effects can potentially worsen narrow-angle glaucoma. Individuals with glaucoma should avoid using phenindamine without consulting an eye specialist. 
• Urinary Conditions: phenindamine’s anticholinergic effects may lead to urinary retention. Individuals with urinary conditions or urinary tract obstruction should use phenindamine with caution and under medical supervision. 
• Thyroid Disorders: phenindamine can interfere with thyroid function tests, leading to inaccurate results. Individuals with thyroid disorders should inform their healthcare provider before undergoing thyroid function testing while taking phenindamine. 
• Liver or Kidney Dysfunction: Individuals with liver or kidney dysfunction may require dose adjustments or careful monitoring while using phenindamine, as these organs are involved in metabolizing and eliminating drugs from the body. 
• Elderly Individuals: Elderly individuals may be more susceptible to the sedative and anticholinergic effects of phenindamine. Careful dosing and monitoring are recommended. 
• Alcohol or substance use disorders: phenindamine’s sedative effects can be enhanced when combined with alcohol or other substances that depress the central nervous system. Individuals with a history of alcohol or substance use disorders should use phenindamine cautiously. 

Pregnancy / Lactation

Pregnancy consideration: Pregnancy Category: not assigned 

Lactation: excreted into breast milk: unknown  

Pregnancy category: 

• Category A: well-controlled and Satisfactory studies show no risk to the fetus in the first or later trimester. 
• <b>Category B: there was no evidence of risk to the fetus in animal studies, and there were not enough studies on pregnant women. 
• Category C: there was evidence of risk of adverse effects in animal reproduction studies, and no adequate evidence in human studies must take care of potential risks in pregnant women.   
• Category D: adequate data with sufficient evidence of human fetal risk from various platforms, but despite the potential risk, and used only in emergency cases for potential benefits. 
• Category X: Drugs listed in this category outweigh the risks over benefits. Hence these categories of drugs need to be avoided by pregnant women. 
• Category N: There is no data available for the drug under this category. 

Pharmacology

Pharmacology: 

phenindamine is an antihistamine medication that exerts its pharmacological effects by selectively blocking the activity of histamine at H1 histamine receptors. Histamine is a naturally occurring chemical released during allergic reactions, leading to symptoms like itching, sneezing, runny nose, and watery eyes.

By binding to H1 receptors, phenindamine prevents histamine from exerting its effects, thereby alleviating allergy-related symptoms. Additionally, phenindamine possesses anticholinergic properties, which contribute to its ability to relieve symptoms like runny nose and help manage conditions involving excessive secretion. It is available in various forms, such as oral tablets or capsules, and is used to provide temporary relief from allergic symptoms.  

Pharmacodynamics: 

• Histamine Receptor Antagonism: phenindamine is an antihistamine that competes with histamine for binding to H1 histamine receptors located on various cells throughout the body, including blood vessels, respiratory tract, and skin. When histamine binds to these receptors, it triggers allergic responses, such as itching, sneezing, and increased vascular permeability. phenindamine’s antagonistic action inhibits histamine from binding to these receptors, thereby preventing or reducing the allergic symptoms caused by histamine release. 
• Anticholinergic Effects: phenindamine also possesses anticholinergic properties, which means it inhibits the activity of the neurotransmitter acetylcholine. This effect contributes to phenindamine’s ability to alleviate certain symptoms associated with allergies, such as runny nose and excessive salivation. 
• Sedative Effects: One of the notable side effects of phenindamine is sedation or drowsiness. This sedative effect is due to phenindamine’s ability to cross blood-brain barrier & interact with central nervous system receptors. As a result, phenindamine may cause drowsiness and impair alertness.

Pharmacokinetics: 

Absorption 

phenindamine is commonly administered orally in the form of tablets or capsules. After oral administration, it is absorbed from the gastrointestinal tract into the bloodstream. The rate & extent of absorption can be influenced by factors such as the formulation of the drug, presence of food in the stomach, and individual variations in metabolism. 

Distribution 

Once absorbed, phenindamine is distributed throughout the body via the bloodstream. It crosses blood-brain barrier, allowing it to exert its effects on central nervous system receptors, leading to sedative and anticholinergic effects. It also reaches various tissues, including those with H1 histamine receptors, where it blocks the action of histamine. 

Metabolism 

phenindamine undergoes hepatic (liver) metabolism. The exact metabolic pathways and enzymes involved are not widely documented in available sources. Metabolism is an important factor that can influence the duration of action and potential interactions with other drugs. 

Elimination and excretion 

The metabolites of phenindamine are eliminated primarily through the kidneys via urine. The exact mechanisms and kinetics of excretion are not well described in available sources. 

Adminstartion

Administration: 

• Dosage: The dosage of phenindamine can vary based on factors such as the individual’s age, weight, severity of symptoms, and formulation of the medication.  
• Timing: phenindamine is usually taken one to several times a day, depending on the formulation and the intended use. Follow the prescribed dosing schedule recommended by your healthcare provider. 
• With or Without Food: phenindamine can be taken with or without food, depending on the formulation and your personal preference.  
• Duration of Use: The duration of phenindamine use will depend on the nature of your condition and the recommendation of your healthcare provider. Follow their instructions for how long to continue taking the medication. 

Patient Information Leaflet

Patient information leaflet 

Generic Name: phenindamine 

Pronounced: (fen-IN-duh-meen)  

Why do we use phenindamine? 

• Allergic Rhinitis: phenindamine is used to alleviate the symptoms of allergic rhinitis, which include sneezing, runny or stuffy nose, itching, and watery eyes. It helps reduce the body’s response to allergens and provides relief from these symptoms. 
• Allergic Skin Conditions: phenindamine can be used to relieve itching and skin discomfort caused by various allergic skin conditions, such as urticaria (hives) and dermatitis (eczema). 
• Allergic Conjunctivitis: For individuals experiencing allergic conjunctivitis, characterized by redness, itching, and watering of the eyes due to allergens, phenindamine can help provide relief from these eye-related symptoms. 
• Pruritus (Itching): phenindamine may be used to alleviate generalized itching caused by allergic reactions or other skin irritations. 
• Insect Bites and Stings: In cases of insect bites or stings that lead to itching and discomfort, phenindamine can be used to help reduce these symptoms.