A prostate cancer drug believed to have kept the man convicted of the Lockerbie bombing alive for almost three years has finally been given the go-ahead for use on NHS patients in Scotland.

Cancer patients and charities yesterday welcomed the decision by the Scottish Medicines Consortium (SMC) to recommend abiraterone, which was used to treat prostate cancer sufferer Abdelbaset Ali Mohmed al Megrahi before he finally succumbed to the disease May.

Scotland is the last part of the UK to accept abiraterone for use on the health service after recent decisions by regulators in England, Wales and Northern Ireland. It comes five months after the SMC had ruled out the drug on cost.

Abiraterone, brand name Zytiga, has been shown in clinical trials to prolong survival for an average of four months when used in conjunction with the drug prednisone or prednisolone.

Al Megrahi, the only man convicted of the Lockerbie bombing, was released from Greenock Prison in August 2009 on compassionate grounds with a prognosis of just three months to live. The length of time he survived was widely believed to be due to abiraterone.

The drug slows the spread of cancer by inhibiting testosterone production and is prescribed to men where chemotherapy has failed and the disease has become terminal.

Owen Sharp, chief executive of Prostate Cancer UK, urged health boards to make it available to patients as quickly as possible.

He said: "This fantastic, if long overdue, news is an absolute triumph for everyone in Scotland who joined us in campaigning for men with incurable prostate cancer to be allowed abiraterone on the NHS.

"Today brings a victory for both decency and common sense.

"Now the correct decision has been made, health boards must waste no time in ensuring men who need abiraterone can access it as soon as possible. Men with incurable prostate cancer should not be subjected to any further delays at a stage in their life when time is at an absolute premium."

Dr Harpal Kumar, chief executive of Cancer Research UK, said he was delighted.

He said: "We know abiraterone is an effective drug. Although it's not a cure, it can offer men crucial extra months at the end of their lives, which can feel priceless to them and their loved ones."

Manufacturer Janssen UK resubmitted its application to have abiraterone approved for use on NHS Scotland after the SMC concluded in March that its price tag – of up to £3000 a month – was not cost-effective.

However, the SMC said it had overturned its original rejection "because the expected benefits of the medicine outweighed its cost when considered in the context of the patient access scheme (PAS)"– a system put in place by a manufacturer to enable patients to access new drugs at a discount.

To date, patients in Scotland have been able to get abiraterone on a case-by-case basis approved by their health board, privately or by joining a clinical trial.

The SMC said its new advice depended on the continuing availability of the PAS in Scotland, allowing the NHS to recoup the same discount and putting the cost closer to £2000 a month. It added that it had also been persuaded by "additional factors such as improvement in life expectancy, quality of life, and evidence of benefits in specific patient subgroups".

The Scottish Conservatives' health spokesman Jackson Carlaw said: "It's a welcome decision, but not before time. This drug should have been available long before now. It has been an injustice that Scottish men have been the only ones in the UK not to have had access to this."

The National Institute for Health and Clinical Excellence approved abiraterone for the NHS in England and Wales in May and Northern Ireland's medicines regulator followed on August 1.