A private equity owned drugmaker is under investigation by the uks competition watchdog after its threats to withdraw one of its bipolar medicines triggered a fierce backlash from doctors over access and pricing.

Essential pharma, which was bought out by swiss private equity firm gyrus capital, in january, planned to pull lithium-based medicine priadel from the market in april 2021, pushing thousands of patients with bipolar disorder towards the companys more costly drug.

The company on tuesday said it had failed to agree a sustainable price for lossmaking priadel with the department of health but would continue to supply the drug after the competition and markets authority announced its probe.

At least one in a 100 people in the uk are diagnosed with bipolar disorder, and of those 20 per cent take lithium tablets. essential pharma makes two of the three lithium carbonate medicines used to treat bipolar disorder in england.

Priadel costs 4.02 for a pack of 100 400mg pills while the cost of essential pharmas lithium-based alternative camcolit is 48.18. the companys most expensive lithium carbonate tablet costs 87 for 100 250mg pills.

Medical groups including the royal college of psychiatrists wrote a letter to matt hancock, health secretary, in september in which they warned these developments will increase cost to the nhs, add pressure on already overstretched primary and secondary care services, and most importantly potentially compromise patient safety.

The groups said switching medicines could be a difficult process with health complications. nhs head sir simon stevens accused essential pharma of using the cover of coronavirus to try and price-gouge british taxpayers.

The cma on tuesday said essentials plans were particularly concerning at a time when the uks national health service was under significant strain during covid-19.

Essential has agreed to keep supplying the drug while negotiating a new price with the government, negating the need for the cma to use its powers to demand it do so. the watchdog said it would continue its investigation until a satisfactory agreement was reached on price.

Ingvild liborg, chief executive of essential, said: we hope that the decision we have made to withdraw our discontinuation notice for priadel will enable us to re-engage in a productive and constructive dialogue with the doh on priadel, which we sell at a loss in the uk and at a price lower than in other european markets.

We look forward to working with both the cma and the doh towards a positive outcome that in particular results in the sustainable supply of priadel to patients in the uk.

The cma could fine essential up to 10 per cent of its global turnover if it was found to have breached competition rules. the agency has taken increasingly tough action on big pharma in recent years for overcharging the nhs and colluding to keep prices high.

Last year the regulator secured the first ever payment to the nhs resulting from a pharmaceutical competition probe when south african company aspen agreed to pay 8m for persuading two of its rivals to stay out of one of its markets.

Andrea coscelli, cma chief executive, said: thousands of people across the uk rely on lithium-based drugs to manage bipolar disorder, so its important that we protect their interests by scrutinising potential competition concerns to reach a fair conclusion as quickly as possible.