(CNN) President Trump is taking a prostate drug often prescribed for hair loss, his physician Dr. Harold N. Bornstein told the New York Times in an interview published Wednesday. He also made a point of stating that the President has all of his hair.

The New York City gastroenterologist also said the President is taking antibiotics to control rosacea, a skin condition that causes redness.

A senior White House official says Bornstein did not have Trump's permission to speak about his health to the Times.

The physician told the Times he has had no contact with his patient since Trump became president. Trump had visited his office every year since 1980 for annual checkups, colonoscopies and other routine tests.

During the campaign, Trump's longtime physician disclosed only that he was taking rosuvastatin and low-dose aspirin to reduce his risk of heart attack.

Bornstein came under scrutiny for a letter he wrote describing Trump's physical health that concluded, "If elected, Mr. Trump, I can state unequivocally, will be the healthiest individual ever elected to the presidency."

What is Propecia?

Propecia is a lower-dose formulation of finasteride that is prescribed to men with enlarged prostate glands under the brand name Proscar.

Originally, the Food and Drug Administration approved finasteride 5 mg (Proscar) in 1992 for the treatment of "bothersome symptoms in men" with an enlarged prostate, which is also referred to as benign prostatic hyperplasia. At that time, the FDA also approved Proscar to reduce the need for surgery related to an enlarged prostate and possible urine retention.

In 1997, the agency approved a lower-dose formulation of finasteride (Propecia) for the treatment of male pattern hair loss, a gradual thinning that leads to either a receding hairline or balding on the top of the head. The FDA does not permit Propecia for treating hair loss in women or children.

"It is a very common medication," said Dr. Louis Kavoussi, chairman of urology at Northwell Health in New Hyde Park, NY. He added that finasteride has been around for decades, so its long-term safety has been demonstrated.

The drug, which blocks the body's production of male hormones, is in a class of medications called 5-alpha reductase inhibitors.

"The effectiveness varies," said Kavoussi, who has no ties to Merck or the companies that make generic versions of finasteride. Though some men who take it for hair loss find it "very effective," others do not. "Same for prostate," he said. "Some men gain quite a bit of symptom relief, other men more modest. It depends on the patient."

Possible side effects of the finasteride include decreased libido, problems with erection and ejaculation, pain in the testicles and depression. According to drugmaker Merck's prescribing information , patients taking the drug should promptly notify their doctor if they experience changes in their breasts, rash, itching, hives, swelling of the face or hands, or difficulty breathing or swallowing.

According to Kavoussi, "most men tolerate it pretty well." Those who do get side effects simply stop taking the medicine, and the effects resolve.

For some years, Merck has been a defendant in liability lawsuits regarding Propecia/Proscar.

About 1,370 lawsuits have been filed as of September 30 by people who claim that they have experienced persistent sexual side effects after cessation of treatment with Propecia and/or Proscar. About 50 of the plaintiffs also allege that the drug has caused or can cause prostate cancer, testicular cancer or male breast cancer.

Dr. Irwin Goldstein, founder of San Diego Sexual Medicine, is serving as an expert witness against Merck in the ligation, work for which he is being paid. He said people come to his clinic "from all over the world" for help with finasteride-associated symptoms.

Many patients experience "a sudden or significant change in libido," he said, while another common side effect is erectile dysfunction. Along with these sexual effects, Goldstein said the drug can cause problems with both mood and cognition, including harmful effects on memory and decision-making.

Some patients believe they suffer from "post-finasteride syndrome," in which their symptoms continue after they stop taking the drug.

Join the conversation See the latest news and share your comments with CNN Health on Facebook and Twitter.

As of March 2015, the syndrome is listed on the National Institutes of Health's Genetic and Rare Diseases Information Center, with the disclaimer that this is not intended as " official recognition" of the syndrome . Still, the National Institutes of Health has sponsored studies, which are now underway, to better understand the effects of finasteride.

"You don't want people to shy away -- and that's the bad thing about lawsuits; people get the impression that something is very bad," Kavoussi said, adding, "it's helped a lot of men."

Merck listed 2015 sales of the drug at $183 million, down from a peak of $447 million in 2010. Other drug manufacturers began producing generic versions in 2013.

Efforts to contact Bornstein for comment have not been successful.