NEW YORK (Reuters) - Columbia Laboratories Inc. said on Friday that U.S. regulators had approved its male hormone-replacement drug Striant, the first drug to deliver testosterone through a tablet adhered to the gums.

Columbia Labs said its drug is able to produce testosterone levels equivalent to those seen in "healthy young men." The company cautioned, however, that it and similar medicines can increase risk of prostate cancer and enlarged prostate.

Striant was approved to treat hypogonadal men. Most currently available treatments are transdermal patches, topical gels or injectable forms of testosterone. Striant is placed in the mouth where the gum meets the upper lip. It then dissolves into a gel that remains in place for 12 hours.

"The greatest preponderance of testosterone deficiencies are among men in their 50s and early 60s because the condition can be part of the aging process," company Chief Executive Fred Wilkinson said in an interview.

Aging men are also most likely to develop prostate cancer. So patients need to be monitored for the cancer before taking testosterone-enhancing drugs, and continue to be monitored afterward for development of cancer signs, Wilkinson said.

"Men who feel a little tired and fatigued, with only slightly decreased testosterone levels should not seek testosterone treatment," Wilkinson said.

Dr. Natan Bar-Chama, director of male reproductive medicine at Mount Sinai Hospital in New York, said no reliable long-term studies have been done to determine the degree of prostate-cancer risk for men taking testosterone.

But Dr. Bar-Chama said he and other doctors routinely prescribe the hormone to men, particularly elderly ones. Patients are tested every three months for prostate-specific antigen levels, and undergo digital exams of the prostate, Bar-Chama said.

"Because of the risk of prostate cancer, nobody should use a testosterone-replacement drug without adequate medical evaluation," said Dr. Len Lichtenfeld, deputy chief medical officer of the American Cancer Society. He said it would be inadvisable for men to use such medicines as "lifestyle drugs."

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