Eye drops and ointments: how they are given and absorbed
- Drugs and toxicity
Most of an eye drop overflows or drains to the nose and into the blood. Good technique makes drops work better and causes fewer side effects.
See it in 3D: Tear drainage · Cornea
What it is
Topical drops are the main way of treating eye disease. A drop is larger than the space between the lid and the eye can hold, so most spills out or drains through the tear duct into the nose, where it is absorbed into the blood without passing through the liver. That explains why beta-blocker drops can slow the heart or trigger asthma. Correct technique, spacing between drops and closing the tear duct improve effect and reduce systemic toxicity.
What to know
- One drop is enough: a second drop at the same time just overflows.
- Wait about five minutes between different drops so the first is not washed out; ointments go last.
- Closing the eyes and pressing the inner corner for one to two minutes reduces absorption into the body.
- The bottle tip must not touch the eye or lashes, to avoid contamination.
- Preservatives (such as benzalkonium chloride) can damage the ocular surface with long-term use.
Toxicity and risks
- Timolol drops can cause bradycardia, heart block and bronchospasm; ask about asthma and heart disease.
- Older people with arthritis, tremor or poor vision often cannot instil drops: ask them to show how they do it.
- Poor adherence is a main reason glaucoma progresses despite treatment.
Next step / Initial management
- Teach the technique at the first prescription and check it at follow-up.
- Patients on beta-blocker drops with asthma, slow pulse or heart block: review with ophthalmology for an alternative.
- Many drops at once: write a schedule with times and the order of drops.
- Persistent irritation with long-term drops: consider preservative toxicity and discuss preservative-free options.
Test yourself
Think of the answer, then tap the question to see it.
Why can timolol eye drops cause bradycardia?
Because much of the drop drains through the tear duct to the nasal mucosa and is absorbed into the blood without first-pass metabolism.
How long should a patient wait between two different eye drops?
About five minutes, so the second does not wash out the first.
How can systemic absorption of eye drops be reduced?
By closing the eyes and pressing the inner corner over the tear duct for one to two minutes.
Elsewhere in DurgiPedia
Connections
See it in 3D2
The structures of Durgical's 3D anatomy where it is found.
In Pharmacology3
Educational content; not a clinical guideline and no substitute for assessment by a health professional. For sudden visual loss, severe eye pain, a chemical burn or an eye injury, go to an emergency department at once.
Sources: Open Angle Glaucoma (StatPearls Publishing (NCBI Bookshelf), 2024); Dry Eye Syndrome (StatPearls Publishing (NCBI Bookshelf), 2024).
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Representative model, for educational purposes only.