Glomerular filtration rate and calcium metabolism in long-term lithium treatment.

Does long-term lithium treatment induce an irreversible renal damage, and does polyuria or changes in the calcium metabolism indicate this? To elucidate these questions GFR, diuresis, S-Ca, S-Mg, S-PTH and bone mineral content (photonabsorptiometry) were determined in 29 consecutive patients on long-term lithium therapy for 2.5--12 years and in 4 patients, who had been admitted to the Renal Clinic with lithium-induced polyuria. Only 1 of the patients had had a known lithium intoxication (S-Li > 2 mmol/l). None had a history of renal disease or significant analgesic consumption. In the consecutive series the GFR was not significantly reduced and no correlations were found between this parameter and the duration of lithium therapy, average S-Li, highest S-Li noted, diuresis or any of the calcium parameters. The morning diuresis was significantly increased in comparison with a control group with normal kidney function. 2 of the 4 polyuric patients had a decreased GFR, but in 1 case it was normalized on desmopressin supplementation. Renal biopsy in the patient with one S-Li of 2.35 and a low GFR in the consecutive series, and in 3 of the polyuric patients, revealed focal interstitial fibrosis and nephron atrophy. The mean S-Ca, S-Mg, S-PTH and bone mineral content were increased, but no significant intercorrelations between these parameters were found. Neither were any intercorrelations found between the calcium parameters and time on lithium therapy, average S-Li, highest S-Li noted or morning diuresis. In conclusion a relatively well-managed lithium therapy for up to 12.5 years does not seem to influence the GFR, even if renal biopsy in 4 of our patients revealed interstitial nephritis and data in the literature indicate a progressive interstitial nephritis. The present study did not support the proposition that polyuria is an alarming sign of pronounced renal lesion. Calcium metabolism is influenced by lithium therapy but from the clinical point of view no negative effects could be found. S-Ca should probably be checked regularly in patients on long-term lithium therapy.

Influence of food on the absorption of phenytoin in man.

The influence of food intake on the absorption of phenytoin was examined in eight healthy volunteers, by study of single-dose kinetics following ingestion of phenytoin 300 mg either with a standardized breakfast or on an empty stomach. Blood samples were collected at regular intervals from 0 to 48 h, and serum concentrations of unmetabolized phenytoin were determined by gas chromatography. Serum concentrations of the major metabolite of phenytoin, 4-hydroxyphenytoin, were measured by mass fragmentography. Concurrent intake of food and phenytoin appeared to accelerate absorption of the drug from the formulation used, and the peak concentrations were significantly higher (mean increase 40%) in the postprandial than in the preprandial state. As reflected by the AUC (area under the curve), the amount of drug absorbed was increased during postprandial conditions, although the difference only reached borderline significance. It is suggested that phenytoin should always be taken in a defined relation to meals.

Vitamin B12 body stores during oral and parenteral treatment of pernicious anaemia.

Oral treatment of pernicious anaemia patients with 1 mg cyanocobalamin daily has been shown before to be as effective as conventional injection therapy. The result of this study indicates that oral treatment also keeps the vitamin B12 body stores adequately filled, a confirmation of earlier results obtained in another way.