A total of 143 deaths were associated with drug treatments last year, according to the State regulatory body, the Irish Medicines Board.

The IMB's latest annual report says it received 2,835 valid new adverse drug reaction reports in 2013, and 143 patients were reported to have died while on drug treatments.

The report points out that in many of these cases, the patients concerned had significant underlying illnesses and would have been treated with multiple medicines and/or surgery, which may also have contributed to the deaths.

In addition, the IMB says, many of these fatalities would have been influenced by disease progression or other complications in relation to the medicine concerned. Other factors included that the drugs may have been used in the management of severe underlying medical conditions.

The medicine associated with the highest number of fatal outcomes was a schizophrenia drug, clozapine, which was linked to 14 reports of fatal outcomes. Next on the list was denosumab, used for a range of bone conditions including osteoporosis, myeloma and treatment-induced bone loss. This was linked to nine deaths.

Of the 2,835 adverse drug reactions reported to the IMB last year, the highest amount, 503, were associated with monoclonal antibodies, which are used to treat cancer, rheumatoid arthritis and other serious conditions.

The next highest was 234 reactions associated with vaccines used in the primary immunisation programme, followed by 214 reactions associated with the schizophrenia drug clozapine.

The IMB says the majority of adverse reactions are notified to it by drug companies marketing the medicines. Most of these reports will have been initially made to the companies by doctors, pharmacists and other health professionals, who may also report directly to the IMB.

Adverse reaction reporting rates were highest for newly-licensed medicines. Reporting rates may also be stimulated by publicity about a particular medicine or reaction, the IMB said.

Adverse reaction reports, it says, may arise from suspicions occurring during observation of an unexpected or unwarranted event in the context of the use of a medicine. They may also include reactions known to occur with medicines as outlined in the supplied product information.

The IMB says the number of reaction reports received cannot be used as a basis for determining the incidence of a reaction, as neither the total number of reactions, nor the total number of patients using a medicine, is known.