Action and Spectrum

Mechanism of action 

epinastine blocks the histamine receptors on these cells, preventing histamine from binding to them and triggering the allergic response. As a result, epinastine can help to reduce allergy symptoms such as itching, runny nose, and sneezing. 

epinastine is also a weak inhibitor of the enzyme acetylcholinesterase, which helps to increase the levels of acetylcholine in the body. Acetylcholine is a neurotransmitter that regulates smooth muscle contraction and dilation of blood vessels. By inhibiting acetylcholinesterase, epinastine can help to relax smooth muscle and dilate blood vessels, which may help to reduce inflammation and swelling in the nasal passages. 

Spectrum 

epinastine is selective for the histamine H1 receptor, which primarily blocks the histamine action at the H1 receptor. Histamine is a chemical involved in the body’s allergic response. The H1 receptor is found on specific cells in the body, including smooth muscle cells, endothelial cells, and certain types of immune cells. By blocking the H1 receptor, epinastine can help to reduce allergy symptoms such as itching, runny nose, and sneezing 

Drug Interaction

Adverse Reaction

Frequency undefined:  

Burning sensation in the eye 

Hyperemia 

Non-ocular infection 

Headache 

Folliculosis 

Pruritis 

Post-marketing reports 

Increased lacrimation 

Black Box Warning

Contraindication / Caution

Contraindications 

• Hypersensitivity to epinastine or any of its ingredients 
• Use of a monoamine oxidase inhibitor (MAOI) within the past 14 days 
• Glaucoma or increased intraocular pressure 
• Prostate hyperplasia or urinary retention 
• Pregnancy (category C) 

Caution 

• Drowsiness: It may cause drowsiness, particularly at higher doses 
• Alcohol: Alcohol can increase the sedative effect of epinastine, so you should avoid drinking alcohol while taking this medication. 
• Pregnancy: It is classified as pregnancy category C, which may harm a developing fetus. You should not use epinastine if you are pregnant unless your healthcare provider determines that the benefits outweigh the risks. 
• Breastfeeding: It is not known if epinastine is excreted in human milk. It would help if you did not use epinastine while breastfeeding unless your healthcare provider determines that the benefits outweigh the risks. 
• Children: The safety and effectiveness of epinastine in children have not been established.  

Pregnancy / Lactation

Pregnancy consideration: may harm a developing fetus 

Pregnancy category: C 

Lactation: Excretion of the drug in human breast milk is unknown 

Pregnancy category: 

Category A: well-controlled and Satisfactory studies show no risk to the fetus in the first or later trimester.   

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 available 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 

epinastine is an antihistamine used to treat allergic conjunctivitis, a type of eye allergy that causes inflammation of the conjunctiva (the transparent outer layer covering the eye’s white part). It works by blocking the action of histamine, a chemical involved in the body’s immune response to allergens.  

Pharmacodynamics 

As a selective H1-receptor antagonist, epinastine blocks the action of histamine at H1 receptors, which helps to reduce inflammation and the symptoms of allergic conjunctivitis. In addition to its effects on H1 receptors, epinastine also has an affinity for other receptors, such as H2 and 5HT2.  

However, its primary mechanism of action is the inhibition of histamine and other mediators involved in the allergic response by blocking H1 receptors. This helps to reduce vascular permeability and the release of histamine and other chemicals that cause inflammation and other allergic symptoms. 

Pharmacokinetics 

Absorption 

epinastine is rapidly absorbed after it is administered as eye drops, with an onset of action within 3-5 minutes. Its duration of action is about 8 hours, which makes it practical to treat allergic conjunctivitis over 24 hours. 

Distribution 

epinastine is about 64% protein-bound, which means it binds to proteins in the bloodstream. This can affect its distribution to different tissues in the body. 

Metabolism 

It is metabolized in the liver and eliminated from the body primarily through urine (about 55%) and feces (about 30%). Its half-life, or the time it takes for the concentration of the drug in the body to be reduced by half, is about 12 hours 

Elimination/excretion 

Its total body clearance, or the rate at which the drug is eliminated from the body, is about 56 litres per hour. These pharmacokinetic parameters can be affected by various factors such as age, kidney function, and the presence of other drugs. 

Adminstartion

Administration 

epinastine is usually administered as eye drops. It is available in a preservative-free formulation, preferred for patients who are sensitive to preservatives or need to use the drops frequently. To administer the drops, the patient should wash their hands, tilt their head back slightly, and gently pull down on the lower eyelid to create a small pocket. The drops should be applied to the pocket, and the patient should gently close their eyes and press on the inner corner of the eye to help the drops spread evenly. It is essential to avoid touching the dropper tip to the eye or any other surface, as this can contaminate the drops. 

The dosage and frequency of epinastine eye drop depending on the severity of allergic conjunctivitis and the response to treatment. However, they should skip the missed dose and continue with their regular schedule if it is almost time for the next dose. It is essential to use only the prescribed dose of epinastine. 

Patient Information Leaflet

Patient information leaflet 

Generic Name: epinastine 

Pronounced: (EP-i-NAS-teen) 

Why do we use epinastine? 

epinastine is used to treat allergic conjunctivitis, a type of eye allergy that causes inflammation of the conjunctiva (the transparent outer layer that covers the white part of the eye)