Nonsteroidal anti-inflammatory drugs (NSAIDs) play a vital role in the treatment of our patients. Thus, we must understand this drug categorys role, its off-label use and its adverse effects; and we must be aware of the exciting forthcoming additions to this medication grouping.
NSAIDs diminish inflammation and mediate pain by inhibiting the activity of cyclooxygenase (COX) enzymes, which catalyze the conversion of arachidonic acid into pros-taglandins and thromboxanesboth powerful mediators of inflammation. However, arachidonic acid may also be acted upon by another enzymelipoxygenasewhich yields a different class of chemical mediators called leukotrienes. Leukotrienes increase microvascular permeability and mobilize/activate white blood cells. As a drug class, NSAIDs do not directly inhibit lipoxygenase. Therefore, they do not address the entire inflammatory cascade. However, at least one NSAIDVoltaren (diclofenac sodium 0.1%, Novartis Ophthalmics)appears capable of reducing the level of leukotriene formation in vitro by an indirect means.1 There is also evidence that NSAIDs have some degree of free radical scavenger activity that may be beneficial in cases of inflammation.2
|Highly symptomatic mechanical keratopathy responds very well to topical NSAIDs.|
Initially, NSAIDS were used for inhibiting intraocular miosis during cataract extraction. But, physicians soon realized that these drugs were effective in the postoperative management of inflammation and pain. Many clinicians have found that NSAIDs are of benefit in a variety of off label clinical situations, such as the prevention and treatment of cystoid macular edema (CME) in post-operative cataract patients. A total of 9% of patients who undergo uncomplicated phacoemulsification still show angiographic evidence of CME.3 A small percentage of these patients may have visual symptoms, particularly if the surgery is prolonged or complicated. Many controlled clinical trials have shown that topical NSAIDs have a beneficial role in the prevention of CME.4-8 And, at least one study showed that topical NSAIDs may improve cases of chronic CME, even when initiated two years after cataract surgery.9 NSAIDs have also been reportedly beneficial in treating CME that can follow Nd:YAG laser capsulotomy.10
The most common use for NSAIDs is in the temporary management of ocular pain due to superficial corneal insult. Because NSAIDs inhibit prostaglandin synthesis, they help to rapidly and effectively break the pain cycle. So, we use these drugs to treat corneal abrasions, corneal foreign bodies, recurrent corneal erosions and chemical keratitis. Typically, we prescribe Acular LS (ketorolac tromethamine 0.4%, Allergan) every 4 hours as needed, over a 24 to 48 hour period. Used judiciously, NSAIDs can often take the place of oral analgesics in alleviating pain. When the inflammation is more severe or deeper in the eye (i.e. when a secondary uveitis is present following corneal insult), NSAIDs and topical steroids can be used concurrently without fear of detrimental interaction.
NSAIDs are not without the potential for adverse reactions, such as corneal melting.11 The problem of corneal melting first surfaced in August of 1999, after members of the American Society of Cataract and Refractive Surgery (ASCRS) responded to an internal survey about complications associated with NSAID use. The news sparked tremendous controversy, ultimately resulting in the withdrawal of generic diclofenac (Falcon Laboratories) from the U.S. market. Similar cases have been reported, implicating various drugs in this category.12-14 While you should certainly take this association into consideration whenever utilizing these agents, no one to date has accurately described the model by which NSAID-induced corneal melting occurs. Moreover, researchers have suggested that this phenomenon is likely a multi-factorial issue, which goes well beyond simple drug toxicity.12
NSAIDs in the Pipeline
In the very near future, you will likely have two new NSAIDs to prescribe: Xibrom (bromfenac sodium 0.09%, ISTA Pharmaceuticals) and Nevanac (nepa-fenac 0.1%, Alcon).
Xibrom received FDA approval in March for the treatment of postoperative inflammation in patients who have undergone cataract extraction. This drug is the first topical NSAID approved for twice-daily dosing (all other medications are indicated for q.i.d. administration). Bromfenac has been used in Japan since 2002 for managing post-surgical ocular inflammation.
Nevanac is currently under FDA review and may receive approval in late 2005. The drugs proposed indication is for the treatment of inflammation and pain following cataract surgery. Nevanac is different from other NSAIDs in that it is a pro-drug converted by enzymatic reaction into a more powerful cyclooxygenase inhibitor known as amfenac sodium shortly after penetrating the ocular tissues. Because of this mechanism, Alcon claims the drug delivers excellent anti-inflammatory efficacy to the cornea, iris/ciliary body and the retina. In addition, Nevanac is extremely bio-friendly, as it boasts a physiologic pH of 7.4 and a very low concentration of benzalkonium chloride (0.005%).
Topical NSAIDs hold an important place in our armamentarium, and the future of these drugs appears very promising. By understanding this drug categorys mechanism, adverse effects and versatility, you can feel confident in prescribing these drugs for a wide range of ocular conditions.
Drs. Kabat and Sowka are members of Alcons Speakers Alliance. They do not have a financial interest in any of the products mentioned.
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