The degree of baldness seems to be a risk factor for lesion development, as men with severe baldness were found to be seven times more likely to have 10 or more AKs when compared to men with minimal or no baldness. This observation can be explained by an absence of hair causing a larger proportion of scalp to be exposed to UV radiation if other sun protection measures are not taken. Diagnosis
Physicians usually diagnose actinic keratosis by doing a thorough physical examination, through a combination of visual observation and touch. However a biopsy may be necessary when the keratosis is large in diameter, thick, or bleeding, in order to make sure that the lesion is not a skin cancer. Actinic keratosis may progress to invasive squamous cell carcinoma (SCC) but both diseases can present similarly upon physical exam and can be difficult to distinguish clinically. Histological examination of the lesion from a biopsy or excision may be necessary to definitively distinguish AK from in situ or invasive SCC. In addition to SCCs, AKs can be mistaken for other cutaneous lesions including seborrheic keratoses, basal cell carcinoma, lichenoid keratosis, porokeratosis, viral warts, erosive pustular dermatosis of the scalp, pemphigus foliaceus, inflammatory dermatoses like psoriasis, or melanoma. Biopsy
A lesion biopsy is performed if the diagnosis remains uncertain after a clinical physical exam, or if there is suspicion that the AK might have progressed to squamous cell carcinoma. The most common tissue sampling techniques include shave or punch biopsy.
Brand name
In India, it is sold under the brand name Metrogyl and Flagyl. In Bangladesh, it is available as Amodis, Amotrex, Dirozyl, Filmet, Flagyl, Flamyd, Metra, Metrodol, Metryl, etc. In Pakistan, it is sold under the brand name of Flagyl and Metrozine. Synthesis
2-Methylimidazole (1) may be prepared via the Debus-Radziszewski imidazole synthesis, or from ethylenediamine and acetic acid, followed by treatment with lime, then Raney nickel. 2-Methylimidazole is nitrated to give 2-methyl-4(5)-nitroimidazole (2), which is in turn alkylated with ethylene oxide or 2-chloroethanol to give metronidazole (3):

Veterinary use
Metronidazole is used to treat infections of Giardia in dogs, cats, and other companion animals, although it does not reliably clear infection with this organism and is being supplanted by fenbendazole for this purpose in dogs and cats. It is also used for the management of chronic inflammatory bowel disease in cats and dogs. Another common usage is the treatment of systemic and/or gastrointestinal clostridial infections in horses. Metronidazole is used in the aquarium hobby to treat ornamental fish and as a broad-spectrum treatment for bacterial and protozoan infections in reptiles and amphibians. In general, the veterinary community may use metronidazole for any potentially susceptible anaerobic infection. The U.S. Food and Drug Administration (FDA) suggests it only be used when necessary because it has been shown to be carcinogenic in mice and rats, as well as to prevent antimicrobial resistance. References
External links
"Metronidazole". Drug Information Portal. U.S. National Library of Medicine. "Metronidazole and Tinidazole". Merck manuals.