Image copyright Merck / New Jersey / USA Image caption Experts will now review the safety of the medicine
The US Food and Drug Administration has approved new antidepressants known as covidien, marketed by Merck in the US.
The pills are a brand-new low dose version of a previous name-brand antidepressant called Celexa.
The agency issued a public health advisory (PHA) after it considered three adverse events reported using the tablets.
Merck offered clarification on three medications that remain on the market.
Image copyright Merck Image caption Celexa tablets can be very expensive
When it gave a seal of approval for the new covidien, the agency urged the drugmaker to closely monitor reported side effects and to present detailed safety data to patients and healthcare professionals.
The advisory was based on the FDA’s review of two men – a 54-year-old male who took the pills for 11 days, and a 46-year-old male who took the pills for two weeks.
“These two adverse events reported by the men were elevated blood pressure in the younger man, and white blood cell elevation in the older man,” the agency said.
Their symptoms were mostly transient, the FDA said, and all were so mild that they did not warrant further investigation.
A spokesperson for Merck said the company had no information on the “predominance” of side effects reported.
“In addition, because it’s in the very early stages of research, we are still in the process of understanding the issues and would expect to further update the PHA with our findings as more data becomes available,” the spokesperson said.
Covidien is a new type of low dose antidepressant developed by Merck in collaboration with the privately-held mental health firm, GlaxoSmithKline.
The FDA said it does not yet know the individual side effects of any number of long-term doses.
But analysts expect Covidien will be a big seller.
Covidien is 90% of the drugs that the drugmaker has commercialised in recent years, and is expected to generate sales of around $600m (£450m) in the US this year, IMS Health said in a note in November.
GlaxoSmithKline shares on the London Stock Exchange have risen by almost 50% since the announcement.
After the initial announcement that the tablets would get a green light, shares in Merck slid 2.5% in pre-market trading.
The FDA already has approval for Celexa. Even though the dosage remains the same and Celexa has been available for more than 30 years, the drug is the subject of a string of controversies.
Some of its marketing claims have been ruled misleading by courts, as the pill is not 100% effective and has been associated with serious side effects.
Walgreens then discontinued Celexa, selling to Eli Lilly instead for $3bn.
Causes of suicide attempt in Britain, 2000-2017 The rate of mental health disorders in the UK has reached an all-time high Source: Samaritans/BfS as of May 2018 Source: Samaritans/BfS as of May 2018
When the pill comes to the UK, insurers are likely to cover the new dosage because patients will not have had the full experience of the old.
“As a large range of products on the market are currently being investigated, we are currently reviewing the clinical data,” a spokesman for UnitedHealth, one of the UK’s biggest healthcare insurers, told the BBC.
Other existing antidepressants continue to be prescribed in the UK, particularly by the GP in GPs in smaller towns and villages. They are far more expensive.
One of the pills used in these conditions is bupropion (Wellbutrin), which is the basis of a new antidepressant called adderall by US drugs giant Eli Lilly.
Another antidepressant developed by AstraZeneca for manic episodes is called venlafaxine.
Controversially, Eli Lilly claims that adderall is now a generic drug so it can be sold for cheaper, generic prices.
Wellbutrin was one of the ingredients in the new tablet Covidien.
Wellbutrin was bought by GlaxoSmithKline and the body charged with overseeing the rights of British medicines has warned NHS drugstores to do a check to see if it is covered before they sell it.