An American priest who said she was plunged into suicidal depression after being dispensed eight times her normal dose of steroids by a Croydon pharmacy wants more than £5million compensation.

The Reverend Cathy Horton is suing retailing group, Lloyds Pharmacy Ltd, claiming the mistake wrecked her life and robbed her of the chance of making millions from a new business venture.

Her counsel, Mr Jeremy Stuart-Smith QC, said the impact of repeated steroid overdoses included weight gain, puffy eyes and hair loss and ended in her trying to hang herself with a computer cable in the Priory Clinic.

However, Coventry-based Lloyds denies any liability to compensate her and is fighting the claim.

Mr Stuart-Smith said in July 2001 a GP prescribed a 28-day supply of Dexamethasone which was eight times the proper dose.

The prescription, he said, was "dispensed without question" by Lloyds branch in Addington Road, Selsdon.

The High Court heard that the pharmacy gave her 55 2mg doses, a near equivalent to the amount prescribed.

However, Robert Moxon-Browne QC, for Lloyds, denied the pharmacist who dispensed the steroids had been negligent.

There was, he said, nothing unusual about the prescription and the words to be taken as directed by your doctor' were clearly inscribed on the bottle.

Rev Horton had for years taken 0.5mg doses of the drug and was unaware of the difference when she took the 2mg tablets daily until the end of July.

When she returned to her home in America, where she also works as a lawyer, Mr Stuart-Smith said a doctor also wrongly prescribed the tablets after reading the label on the Lloyds bottle.

Still unaware of the overdoses, Rev Horton continued to take the drug daily.

Mr Stuart-Smith said she soon started to feel lethargic and despite frantic efforts to maintain her fitness by running five or six miles-a-day, by the end of October she was "very ill". Rev Horton was admitted to hospital on numerous occasions and was "completely unfit for work".

She suffered depression along with "psychotic symptoms" and while in The Priory in early 2002, she spent much of the time lying in the foetal position before attempting to hang herself.

Mr Stuart-Smith added: "The case against Lloyds was, and remains, that they were negligent in not questioning the prescription and in dispensing Dexamethasone."

He said that Rev Horton was setting up an "innovative consultancy" in London. The venture - in which she was a 50 per cent beneficial shareholder - was within six months "showing every sign of exceptional success", he told the judge.

However, Mr Moxon-Browne, argued the consultancy business was "doomed to fail".

He also insisted that she probably recovered physically within a few months of her return to her normal dose and now had the same earning potential as she had before.

Mr Moxon Browne put it to Rev Horton that, far from being on good terms with her employers at the time of her illness, she had in fact had a "massive falling out" with the law firm.

However, according to Mr Stuart-Smith because of her illness the company went into liquidation in August 2002.

The hearing, expected to last three weeks, continues.