The parents of young people who have killed themselves and patients unable to have sex are calling for the NHS to stop prescribing acne drug Roaccutane.
Ed Henthorn said it had caused him erectile dysfunction, psychosis and suicidal thoughts.
And one man who believes his son killed himself after taking the drug said the risks "are just too high".
Manufacturer Roche said "millions of patients worldwide have benefited from taking the drug".
The majority of those who take the drug have a positive experience.
"I used to think about girls… but my feelings, thoughts, just faded away," Ed Henthorn told the BBC's Victoria Derbyshire programme.
He was 19 when he took Roaccutane. He describes his acne as mild but bad enough to want to treat.
After three weeks he started to experience side-effects, including reduced energy and sex drive.
Then he experienced erectile dysfunction.
"That was why I decided to stop taking it," he said.
What does the NHS say about Roaccutane?
In its guidance about the options available for acne treatment, the NHS says Roaccutane (isotretinoin) is only recommended for severe cases of acne that haven't responded to other treatments.
The NHS acknowledges there have been reports of people experiencing mood changes while taking the drug. Its advice says, while there is no evidence these changes were caused by Roaccutane, patients should speak to their doctor immediately if they feel depressed or anxious, or if they have feelings of aggression or suicidal thoughts.
Roaccutane, the brand name the drug isotretinoin is most commonly marketed under, is used by about 30,000 people in the UK each year.
Campaigners want it banned from NHS prescriptions, arguing its continuing side-effects mean its risks outweigh the benefits.
Mr Henthorn said he still suffers five years after his last dose.
He said it had thwarted his hopes of completing university and pursuing a career.
"I had psychosis, psychotic symptoms, suicidal thoughts. It was pretty overwhelming," he added.
"My life now is not the best. I'm just kind of at home. The drug's just turned my life upside down."
Warnings about depression and other psychiatric side-effects were added to the drug's patient information leaflet in 1998.
Two years ago, a new warning was added to say some people would be affected by problems getting or maintaining an erection and lower libido.
But Roche said while Roaccutane had side-effects – "like most medications… millions of patients worldwide have benefited from taking the drug".
It added: "Isotretinoin was a prescription-only medicine and therefore can only be safely used under the care and supervision of suitably qualified healthcare professionals.
"This way, specialists with the most experience can advise patients about the important safety issues associated with isotretinoin."
Another version of the drug is marketed by Alliance.
It said it continually assessed the benefits and risks of its medicines.
Many people say it has boosted their self esteem and mental health by treating the acne.
Sarah Perkins makes YouTube videos about coping with acne.
"I would go as far as to say it's a wonder drug," she says. "I feel so much happier. I'm confident in my own skin."
Dematologist Dr Juber Hafiji said it was a very effective treatment for acne.
"In experienced hands it's a very safe treatment, providing the patient is monitored closely, with regular supervision and blood tests at intervals," he said.
David Healy, professor of psychology at Bangor University, said there were many other drugs that could affect someone's ability to have sex.
But the issue with Roaccutane, he added, was how serious the problem could be and how long it could last for.
"It's very, very, important the label makes it clear that these problems can be enduring and also makes it clear that they may only appear after you stop the drug," he said.
The safety of drugs is governed by the MHRA, and the NHS drug approval body NICE follows its advice.
NICE is planning to publish guidance on all acne treatments by 2021 and said it always considered the safety of drugs in its guidelines.
The drug can be prescribed in Scotland, although the Scottish Medicines Consortium said it would not have assessed Roaccutane because it predates the creation of the SMC.
Derek Jones's son Jesse had two courses of Roaccutane, and experienced side-effects in relation to his sex drive.
It led him to take Viagra, aged 24.
Jesse later died, in 2011.
The coroner at Jesse's inquest recorded a narrative verdict. His use of Roaccutane was not considered as a contributing factor.
But Mr Jones believes his son took his own life.
In a draft email found by his parents, Jesse hadRead More – Source