Why do I feel a burning sensation in the eyes after the eye drops using?

Question: Why do I feel a burning sensation in the eyes after using the eye drops that contains antazoline and tetrahydrozoline?

Answer: The eye drops contains antazoline and tetrahydrozoline. It can make blood vessel contraction and acts as antihistamine. The eye drops is indicated for the treatment of allergic reaction, irritation or itching and swelling of eyes due to allergies to chemicals, pollen or weather.

The acidity (pH) for stability of the eye drops is about 5.4, and pH of human tears normally is 7.4, so this may cause eye irritation or eye burning.

However, product of eye drops may have the pH in the range 4.5 to 11.5, because the human tears can dilute the acidity of the drug into normal (=7.4). So, after using the eye drops for a moment, symptoms like burning eyes are gone.

There are also reports that antazoline and tetrahydrozoline cause adverse drug reaction such as, eye irritation and burning sensation after using the eye drops. If the symptoms of burning eyes occur unusual, severe and occur for a long time, it is advised to stop using the drug immediately. And you should return to the hospital where you received treatment in order to be determined the exact cause, or a change to another drug.

References:

1. Beringer P, editor. Remington's the science and practice of pharmacy, 21st ed. Philadeiphia: Lippincott Williams & Wikins; 2006.

2. Hista-Oph®- product information.

3. Antazoline. In: DRUGDEX System [database on the Internet]. Ann Arbor (MI): Truven Health Analytics; 2014. Available from: www.micromedexsolutions.com.

4. Tetrahydrozoline. In: DRUGDEX System [database on the Internet]. Ann Arbor (MI): Truven Health Analytics; 2014. Available from: www.micromedexsolutions.com.