Homatropine hydrobromide calms anterior chamber reaction in bacterial keratitis
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Homatropine is often used in our practice because it complements steroid and nonsteroidal anti-inflammatory drug (NSAID) therapy. In the case of bacterial keratitis, it gives us an option to help calm the anterior chamber reaction without resorting to steroids early in the course of treatment. Seldom is homatropine used by itself, but as additive treatment it plays an important role in primary care optometry.
Homatropine hydrobromide is supplied in 2% solution (0.01% BAK) and 5% solution (0.005% BAK). It is available in generic form or from Ciba Vision and Medical Ophthalmics. It is supplied in 5-mL bottles, and Ciba Vision has homatropine available in sterile 12 x 1-mL dropperettes. The bottles come with red caps, which help patients know which drop to use. I also warn the patient that eye medicine with a red cap should be kept away from children, and this is a strong drop that should only be used as directed by the eye doctor.
Blocks responses
This anticholinergic drug blocks the responses of the iris sphincter muscle and the accommodative ability of the ciliary muscle. This blockage produces mydriasis and cycloplegia within 30 to 60 minutes of instillation, usually by 40 minutes. Recovery requires from 1 to 3 days. Homatropine is about 1/10 as potent as atropine and does not produce as strong of a cycloplegia. It is formulated, in part, as a synthetic and, in part, from the plants of the Solananac family.
Homatropine is not as effective in darkly pigmented irides and may require prescribing the 5% dosage more often than when treating lighter colored eyes. It is my observation that the pupil of an inflamed eye being treated with homatropine usually dilates to only two-thirds of the normal mydriasis compared to the healthy eye. As the inflammation subsides, the pupil increases in size over the course of treatment.
Side effects
The following ocular side effects are often seen with homatropine use:
- stinging or burning on instillation (common, but not a reason to discontinue drops);
- photophobia;
- allergic contact dermatitis of lids;
- erythema with pruritus and edema;
- angle-closure glaucoma; and
- increased intraocular pressure in patients with open-angle glaucoma.
Systemic side effects are more often seen in children or elderly patients in poor health. Caution should be exercised when prescribing anticholinergic drugs for patients with light pigmentation, Down's syndrome and brain damage or spastic paralysis. Systemic side effects include:
- diffuse cutaneous flush (red);
- thirst (dry);
- fever (hot);
- tachycardia (fast pulse); and
- excitement & hallucinations (mad as a hatter).
Condition and dosage
Points to Consider When Prescribing Homatropine: |
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To treat anterior uveitis, Pred Forte (prednisolone acetate, Allergan) should be given four times daily to every hour depending on the severity of the inflammation. Homatropine 2% should be given twice daily to four times daily for mild anterior uveitis. Homatropine 5% can be given twice daily to four times daily for moderate to severe anterior uveitis. Ibuprofen, oral steroids or subconjunctival steroid injections are additional treatment options.
To treat ocular injury, such as abrasion, foreign body removal and blunt trauma, homatropine 2% or 5% can be given twice daily to four times daily depending on the severity of injury. Antibiotics, NSAIDs, steroid therapy and/or oral pain medication may also be required.
To treat bacterial keratitis (corneal ulcer), use homatropine 2% four times daily when a mild to moderate anterior chamber reaction is present. Homatropine 5% four times daily should be prescribed for moderate plus to severe anterior chamber cells and flare. Ciloxan (ciprofloxacin HCl, Alcon) two drops every 15 minutes for 6 hours and then every 30 minutes for 18 hours should be prescribed. Polysporin Ophthalmic Ointment (polymyxin B-bacitracin, Burroughs Wellcome) and ibuprofen are additional medications needed for moderate to severe bacterial keratitis.
For corneal burn (UV burn, chemical burn, welding burn), use homatropine 2% or 5% twice daily to four times daily depending on the severity of the burn. Antibiotics, steroids and/or ibuprofen or oral pain relievers may also be needed.
To treat ophthalmic herpes zoster uveitis, use homatropine 5% four times daily until the disease runs its course. The cycloplegia relaxes the ciliary spasms, thus relieving pain. Pred Forte is usually needed to help calm the uveitis.
For severe cases of epidemic keratoconjunctivitis, homatropine relieves ciliary spasms, making the patient more comfortable. Usually homatropine 2% twice daily is sufficient. Maxitrol (dexamethasone, Alcon) twice daily and Voltaren (diclofenac sodium, Ciba Vision) twice daily may also help relieve inflammation and patient symptoms. Saline rinses, cold compresses and lubricants are supportive therapies that offer some relief.
Discomfort is spared
Homatropine helps relieve pain and reduces the anterior chamber reaction in a wide range of conditions commonly seen in a primary care optometric practice. When homatropine is used judiciously with the primary treatment medication, the patient usually responds more rapidly and is spared discomfort from ciliary spasm. It is an integral part of the treatment plan for anterior uveitis and bacterial keratitis.
For Your Information:- Ciba Vision can be contacted at 11460 Johns Creek Parkway, Duluth, GA 30097-1556; (800) 845-6585; fax: (770) 418-4000; Web site: www.cvo-us.com.
- Medical Ophthalmics can be contacted at 40146 U.S. Highway 19 North, Tarpon Springs, FL 34689; (813) 943-9400; fax: (813) 938-8430.
- Bobby Christensen, OD, FAAO, is in private practice and lectures widely on therapeutic pharmaceutical agents. He can be reached at Heritage Park Medical Center, 6912 E. Reno, Suite 101, Midwest City, OK 73110; (405) 732-2277; fax : (405) 737-4776. Dr. Christensen has no direct financial interest in any of the products mentioned in this article, nor is he a paid consultant for any company mentioned.