Overdose data highlight scale of tricyclics risk
SSRIs are responsible for just 7 per cent of all deaths caused by antidepressant overdose, unpublished Government statistics show.
Antidepressant overdose was the cause of 3,959 deaths in England and Wales over seven years, reveals an analysis by the Office of National Statistics.
But the researchers found tricyclics carried a dramatically higher risk of fatal overdose than SSRIs (see table below).
Study leader Professor Azeem Majeed said the media frenzy surrounding the urgent Government inquiry into
SSRI safety meant GPs were faced with patients refusing to take the newer drugs even though they were much less toxic and better tolerated than tricyclics.
Some 79 per cent of all fatal antidepressant overdoses are suicides, according to the analysis by Professor Majeed, a south London GP and medical epidemiologist at the ONS. The findings will be published in a future edition
of Health Statistics Quarterly.
Dr Nick Dunn, a GP in Hampshire and honorary consultant to the World Health Organisation drug safety monitoring centre, said the findings were 'very interesting'. He added: 'I would not want to prescribe a tricylic to a relative of mine. I would prescribe an SSRI. Tricyclics are toxic drugs which are particularly dangerous in overdose, predominantly due to their cardiac effects. SSRIs do not have these effects.'
Dr Dunn said: 'I believe most GPs would like to prescribe SSRIs most of the time the only thing that has put them off is price.'
Professor Hugh McGavock, professor of prescribing at the University of Ulster and a former member of the Committee on Safety of Medicines, was 'surprised' by the data.
He said tricyclics should not be initiated by GPs because they were only appropriate in patients with severe depression who should be seen by specialists.
He added: 'With tricyclics, due to the unpleasant side-
effects, GPs use about half the recommended dose. This might not have the effect of treating the depression but allows a patient to use it for suicidal purposes.'
The Committee on Safety of Medicines is due to report on its Government-ordered inquiry into the risk of suicidal ideation and dependence associated with SSRIs.
Fatal overdose risk associated with different antidepressants
Drug GP prescriptions Fatal overdoses per
written (2002) 100,000 prescriptions
Amitriptyline 4.7 million 5.1
Dothiepin 2.9 million 6.8
SSRIs AND RELATED DRUGS
Fluoxetine (Prozac) 4.2 million 0.4
Paroxetine (Seroxat) 3.7 million 0.3
Venlafaxine (Efexor) 2.1 million 1.7
Source: ONS data 1993/2000