That is despite existing NHS guidance saying there "appears to be no clinical reason to restrict the number of tablets" of Viagra prescribed to an individual.

BBC: Viagra on NHS 'should be limited to two pills a month'

According to drug data tracker IMS Health, Zocor was prescribed 94 million times in 2010, double the number of prescriptions in 2007.

FORBES: FDA Limits High-Dose Zocor, Backing Earlier Concerns For Second-Most Prescribed Drug

They take complex antiretroviral drugs which can interact with a number of over-the counter and commonly prescribed medicines.

BBC: Condoms

It said NHS boards should target areas for further improvement, such as identifying where particular drugs are over or under-prescribed and supporting GPs to review patients who take a number of different medicines.

BBC: Scots GPs 'could save NHS ?26m'

Earlier, Stuart Denney, prosecuting, told the court Gilliard had suffered from depression a number of years earlier but had stopped taking tablets prescribed by doctors.

BBC: Frederick Gilliard jailed for killing wife with statue

An alarming number of hospitalizations are related to failure to take medications as prescribed or taking medications incorrectly.

FORBES: Are Your Aging Parents Taking Too Many Pills?