[Risk of drug-induced agranulocytosis: an approximation to risk analysis arising from spontaneous notification of agranulocytosis cases among patients treated with calcium dobesilate].
BACKGROUND
Frequently, decisions about the safety of drugs are based on isolated cases of patients that develop a disease, while they have been taken a drug. A new method to detect, using spontaneous reporting, increases in agranulocytosis risk among patients treated with calcium dobesilate is shown.


METHODS
Using data of dobesilate sales, the maximum number of patients treated in a year was calculated. Spontaneous reports of agranulocytosis associated to dobesilate notified along the period 1985-2000 were identified. The number and the maximum number of cases explained by the agranulocytosis risk in a general population were calculated using the distribution of Poisson, assuming several reporting rates. Similarly, the influence of number of patients older than 60 and the duration of exposure to the drug were analysed.


RESULTS
The number of spontaneously reporting cases of agranulocytosis associated to dobesilate, in the period 1985-2000 was not greater than the maximum number of cases predicted by the agranulocytosis risk in a general population. Probably, a high number of dobesilate-treated patients had an advanced age and/or took the drug during several months. In these conditions, it is more difficult to identify an increase of risk associated to drug.


CONCLUSIONS
To calculate the risk of agranulocytosis associated to a drug is required to consider the basal risk of agranulocytosis in a general population as well as its possible modifications in the population of patients treated with the drug.
Zapater Hernández
P
P
Unidad de Farmacología Clínica, Hospital General Universitario de Alicante, c/Maestro Alonso, 109, 03010 Alicante. zapater_ped@gva.es
Horga de la Parte
J F
JF
García
A G
AG
D016907:Adverse Drug Reaction Reporting Systems; D000368:Aged; D000369:Aged, 80 and over; D000380:Agranulocytosis / Q000139:chemically induced* / Q000453:epidemiology; D000465:Algorithms; D002123:Calcium Dobesilate / Q000009:adverse effects*; D016022:Case-Control Studies; D005060:Europe / Q000453:epidemiology; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D007557:Israel / Q000453:epidemiology; D008297:Male; D008875:Middle Aged; D015337:Multicenter Studies as Topic; D016012:Poisson Distribution; D011446:Prospective Studies; D018570:Risk Assessment; D013030:Spain / Q000453:epidemiology
D002123:Calcium Dobesilate