Effects of long-term treatment with procaine amide. A prospective study with special regard to ANF and SLE in fast and slow acetylators.

During 1970-75 a total of 42 patients have been subjected to long-term treatment with procaine amide (PrA) because of different cardiac arrhythmias and have been observed up to over 5 years. Among these patients 35 (83%) developed a significantly increased titer of ANF and of these, 12 patients (29%) developed a "classical" drug-induced SLE syndrome. In the SLE group all but 2 improved rapidly after cessation of PrA, and the ANF titer decreased continuously but slowly in both groups. Acetylation test with sulphamidine and/or isoniazid in 11 patients among the SLE cases showed 8 slow and 3 fast acetylators. Among 12 patients who also had received PrA for a long time, but had not shown any signs of an SLE syndrome, there were 10 fast and 2 slow acetylators.