Analgesic nephropathy in Belgium is related to the sales of particular analgesic mixtures.

Analgesic nephropathy, a chronic progressive renal disease induced by the abuse of drugs containing analgesics and potentially addictive substances (e.g. caffeine, codeine), continues to be a serious problem in Belgium. A recent investigation (1990) of Belgian dialysis patients, including 54 of the 55 dialysis centres, established that 15.6% of the patients had analgesic nephropathy, showing a small decrease in prevalence compared to the 1979 and 1984 estimates. Considerable changes were observed in the sales figures of analgesic during the period 1983-1991. Phenacetin completely disappeared from the market and single analgesics, particularly paracetamol, gained large market shares. The total sales of single analgesics slowly increased, whereas the sales of analgesic mixtures decreased from 12.5 million to 8 million packages per year. In recent years the composition of most analgesic mixtures has been reduced to a single analgesic component in combination with caffeine and/or codeine. In comparing the geographical distribution of the sales of different analgesic products (1983) with the prevalence of analgesic nephropathy (1990), a strong correlation could be observed with particular analgesic mixtures, whereas this was not the case with single analgesics. This observation suggests that a careful analysis of sales data showing a high volume of analgesic mixtures sold, containing two analgesic substances combined with potentially addictive components, is a pharmacoepidemiological indicator for the presence of analgesic nephropathy in a given population.