An acne drug is being investigated by the medicines regulator over concern it may increase the risk of depression.
Dianette is used to treat severe acne
The Medicines and Healthcare Products Regulatory Authority (MHRA) has ordered the review into Dianette, which is also used as a contraceptive.
The charity April (Adverse Psychiatric Reactions Information Link) submitted a dossier on the drug.
April says it has details of more than 100 women who say they became seriously depressed after taking Dianette.
Dianette is licensed as a hormone treatment for severe acne, but only in cases where other treatments, such as oral antibiotics, have not worked.
It is also an effective contraceptive, but doctors have been warned that they should not prescribe it solely for that purpose because it has a higher risk of blood clots than other similar combination pills.
Women who take it are supposed to stop within three or four months of their skin problems clearing up.
However, April says that it knows of some women who have been taking the drug for years.
The manufacturer's information leaflet does warn that one possible side effect of taking the drug is "mild depression".
Millie Kieve, who runs April, said it was clear that this was an under-statement.
She said: "The doctor should warn these girls that if they are depressed, it could be Dianette, instead of putting them on antidepressants."
Ms Kieve said she had been told by the MHRA was particularly concerned by the charity's evidence that doctors were continuing to prescribe Dianette solely as a contraceptive.
The MHRA said it was hoped the findings of its review would be submitted to its expert advisory group on medicines for women's health at the end of May.
The authority granted a licence to an identical pill called Clairette in March - but said there was no reason at the time not to.
In a statement it said: "Depression is a known side effect of Dianette and the product information contains warnings on this issue.
"The description of psychiatric reactions in the product information for healthcare professionals and patients is currently being reviewed by the MHRA.
"The product information (including the Patient Information Leaflet) will be updated if necessary.
"Patients who have concerns about Dianette should discuss the matter with their pharmacist or doctor at a routine appointment."
A spokeswoman for Schering Health Care, which manufactures Dianette, said: "Severe depression is listed in the patient information leaflet as a reason for stopping Dianette immediately. Depressive moods are also listed as a possible side effect.
"Dianette has been used internationally since 1985, and there is therefore 50 million treatment years of experience of use of the product globally.
"We share relevant data with the MHRA and patient safety is obviously of paramount concern."