Arctostaphylos uva-ursi is the plant known as uva ursi. It is also commonly referenced as bearberry, upland cranberry, or kinnikinnick. It is a member of the Ericaceae or Heath family of plants.  Uva ursi is a decumbent plant growing up to 1.5 meters long, as a creeping espalier with elastic, red-brown branches. The plant produces flowers, which are white or reddish with a unique red border. Its fruit is a globose, pea-sized, scarlet, floury drupe. 
Uva ursi spread from the Iberian Peninsula across Central Europe to Scandinavia and Siberia. It is also found in the Altai Mountains, the Himalayas, and in parts of Northern America.  The leaves of this plant are the parts of the plant used medicinally. Interestingly, its modern preparations do not deviate much from its traditional applications, as the usage of the uva ursi leaf was first employed approximately eight-hundred years ago.
The main constituents in uva ursi are hydroquinone glycosides, accounting for some 4 - 15% of the chemical content; the most important of which are arbutin and methylarbutin. Uva ursi also contains polyphenols, tannins (increased in older leaves), flavonoids (quercetin), resin, acids (ursolic, gallic, ellagic), allantoin, and volatile oils (triterpene alkaloids). [3-5]
The glycoside arbutin appears to be very important to the pharmacologic activity of uva ursi. Arbutin is ‘split’ into a small sugar molecule and a hydroquinone in the intestine. In fact, hydroquinone is the compound that exerts effect upon the urinary tract. Once it is made water-soluble in the liver, it can be carried to the kidneys where, if the urine is alkaline, hydroquinone will be released from its carrier.  In the urine, hydroquinone can act as a powerful anti-microbial agent, explaining its ability to address urinary tract infections. 
Arbutin has also been shown to increase the anti-inflammatory and anti-allergic action of some pharmaceuticals, such as dexamethasone. [8, 9] Another isolated compound, corilagin, has been shown to potentiate the activity of beta-lactam anti-biotics against methicillin-resistant Staphylococcus aureus.  Aqueous extracts of A. uva ursi have also demonstrated diuretic effects in animal studies and show the ability to inhibit melanin synthesis by blocking tyrosinase, which is responsible for the conversion of dopamine to melanin. [11-12]
Medicinal actions ascribed to uva ursi include;
Traditionally, it was used as a as a diuretic and a sedative for the genitourinary system, exerting an astringent and tonifying effect. Uva ursi was also used for the treatment of diabetes-related disorders. 
The main application of uva ursi receiving the greatest investigation is within the treatment of urinary tract infections. The only double-blind, placebo-controlled study on uva ursi examined the prophylactic effect of a standardized extract on recurrent cystitis in 57 women.  At the end of one year, 5 of the women in the placebo group had a recurrence while none of the women receiving uva ursi extract had a recurrence. Furthermore, no side-effects were reported in either group. The German Comission E recommends its use for inflammatory disorders of the urinary tract, as well.
Uva ursi may also be useful in treating other inflammatory disorders. A study comparing the effects of arbutin and indomethacin on Type IV allergic reaction-induced immuno-inflammation was conducted.  The results showed that at an oral dose of 50mg/kg of arbutin rapidly decreased the swelling of PC-CD (picryl-chloride induced contact dermatitis) 24 hours after administration. Furthermore, potentiation was demonstrated as arbutin plus indomethacin (subcutaneously) showed inhibitory effects on the swelling of PC-CD and SRBC-DTH (sheep red cell delayed type hypersensitivity) stronger than that of indomethacin alone.
In addition, uva ursi may be beneficial for patients with hyperpigmentary disorders and coughs, particularly of the chronic variety. [12, 16]
Dosages are dependent on the type of preparation and the intended condition to be treated. Generally, cold water extractions of powdered leaves provide higher levels of arbutin, while extracting lower amounts of tannins.  If using a 1:2 strength liquid extract, a range of 4 - 8 ml per day is often a sufficient dose, while a 1:5 extract would require 10 - 17 ml daily. Tablets standardized to contain 70mg arbutin are more easily taken at a dose of 2 tablets, 2 - 3 times daily.
To improve uva ursi’s effectiveness in treating urinary tract infections, the urine must be alkaline. To achieve alkalinity, an alkaline-forming diet, alkalinizing products, or bicarbonate can be recommended. 
Uva ursi should be utilized with caution and is never advised for long-term use. It should be avoided during pregnancy due to an oxytocic effect, as well as in lactating mothers.  Children under 12 should also avoid uva ursi use due to speculation of possible liver impairment from metabolites and its inhibition of B cell maturation in vitro. [18, 19]
Considering the tannin content, organic kidney disease is a contraindication.  Some medications may interact with uva ursi. Because arbutin converts to hydroquinone in alkaline urine, urinary acidifiers can theoretically inhibit this conversion.  As well, the high level of tannins can interfere with absorption of various nutrients, including iron.
The tannins can also cause a gastric irritation if used for too long or in too high of a dose. Toxicity symptoms have been observed with a dose of 15 grams of fresh leaves (providing the equivalent of 1g hydroquinone). The hydroquinone portion is highly toxic and mutagenic.  Toxicity symptoms include; tinnitus, nausea, vomiting, sense of suffocation, shortness of breath, cyanosis, convulsions, delirium, and collapse. 
A case report was published of a woman who developed bilateral bull’s eye maculopathy after ingesting uva ursi for 3 years.  The authors conclude that uva ursi, as a known inhibitor of melanin synthesis, should be added to the list of possible retinal toxic agents.
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