A glitch with the Scottish GP system GPASS could have resulted in smokers trying to quit the habit being mistakenly prescribed anti-impotence drug Viagra by doctors.

NHS Greater Glasgow and Clyde Health Board said the error was due to a computer glitch at two city GP practices, according to a report by BBC Scotland.   The Health Board has issued an alert to practice about the potential problem.

Rather than receiving a prescription for Zyban as prescribed by their GP the GPASS computer system instead incorrectly selected sildenafil, the generic name for Viagra.

The e-Formulary facility provided within GPASS system is configured by individual health boards who set the formulary within it.  It is desigend to enable GPs to pick appropriate drugs from a drugs dictionary or formulary when they fill out a prescription.

Dr Kenneth Harden, the clinical directore for GPASS told EHI Primary Care: "This is extraodinarily unusual situation, which we are taking very seriously."  He said that he had not known a similar problem occur in 10 years of using GPASS.

 A GPASS spokesperson told EHI PC that the problem existed had occured in a Glasgow-specific e-Formulary system used in conjunction with GPASS.

The GPASS spokesperson told EHI Primary Care "no incorrect prescription was issued or dispensed" to any patients.

A health board spokeswoman told the BBC: "At no time was patient care affected by this as all prescriptions are subject to stringent double checking."

NHS Greater Glasgow and Clyde Health Board said it was made aware of the problem on Tuesday and alerted all its GPs to the problem.

A health board spokeswoman said: "A computer glitch was discovered by two Glasgow GP practices that use the Glasgow e-Formulary, following a recent update of the online GPass system used throughout Scotland.

"As a precaution an advisory e-mail and memo was issued to all practices which use GPASS and have installed the e-Formulary to alert staff."

The spokesperson added: "At no time was patient care affected by this, as all prescriptions are subject to stringent double-checking by both prescribing doctors and pharmacy staff."