Peripheral Ulcerative Keratitis (PUK) is a group of destructive inflammatory diseases involving the peripheral cornea in human eyes. The symptoms of PUK include pain, redness of the eyeball, photophobia, and decreased vision accompanied by distinctive signs of crescent-shaped damage of the cornea. The causes of this disease are broad, ranging from injuries, contamination of contact lenses, to association with other systemic conditions. PUK is associated with different ocular and systemic diseases. Moorens ulcer is a common form of PUK. The majority of PUK is mediated by local or systemic immunological processes, which can lead to inflammation and eventually tissue damage. Standard PUK diagnostic test involves reviewing the medical history and a completing physical examinations. Two major treatments are the use of medications such as corticosteroids or other immunosuppressive agents and surgical resection of the conjunctiva. The prognosis of PUK is unclear with one study providing potential complications. PUK is a rare condition with an estimated incidence of 3 per million annually. Signs and symptoms
The most easily identifiable sign is a visible lesion of the cornea presented usually in a crescent shape. Common reasons for destruction are stromal degradation and epithelial defects on the inflammatory cells. There would be a change in conformation of the peripheral cornea, depending on the severity of corneal thinning. This process is usually accompanied by the possibility of concealing perforation.
In the UK, this product was known as PepcidTwo until its discontinuation in April 2015.Famotidine has poor bioavailibility (50%) due to low gastroretention time. Famotidine is less soluble at higher pH, and when used in combination with antacids gastroretention time is increased. This promotes local delivery of these drugs to receptors in the parietal cell membrane and increases bioavailibility. Researchers are developing tablet formulations that rely on other gastroretentive drug delivery systems such as floating tablets to further increase bioavailibility. Society and culture
Certain preparations of famotidine are available over the counter (OTC) in various countries. In the United States and Canada, 10 mg and 20 mg tablets, sometimes in combination with an antacid, are available OTC. Larger doses still require a medical prescription. Formulations of famotidine in combination with ibuprofen were marketed by Horizon Pharma under the trade name Duexis. Research
COVID-19
At the start of the COVID-19 pandemic, some doctors observed that anecdotally some hospitalized patients on famotidine in China may have had better outcomes that other patients that were not taking famotidine. This lead to hypotheses about use of famotidine in treament of COVID-19. Famotidine was researched for potential benefit in treating COVID-19 following hypotheses at the start of the pandemic that it may be an applicable medication. No good evidence of benefit was found. Veterinary uses
Famotidine is given to dogs and cats with acid reflux. Famotidine has been used in combination with an H1 antagonist to treat and prevent urticaria caused by an acute allergic reaction. References
External links

"Famotidine". Drug Information Portal.