The pharmacokinetics of primaquine (PQ) and its major carboxylic acid metabolite (PQC) have been studied in seven Indian patients with P. vivax malaria following PQ 15 mg/day p.o. for 14 days. After a single oral dose on Day 1, a mean peak blood concentration of 50.7 ng/ml PQ was attained after 2.3 h, which declined monoexponentially with a half-life of 5.6 h. The mean total body clearance was 37.6 l/h and the volume of distribution was 292 l. The mean renal excretion (0-24 h) of the drug was only 0.54% of the dose and renal clearance was 0.189 l/h. Following chronic administration, none of the pharmacokinetic parameters was affected, and a steady state blood concentration of 2.5-4.2 ng/ml PQ was attained. After the first dose of PQ, PQC had a mean area under the blood concentration - time curve 11-fold higher than that of the parent drug. In contrast to the rapid distribution and elimination of PQ, the metabolite showed a longer mean residence time and accumulation in the body. The mean Cmax and AUC of the metabolite on Day 14 were 48 and 40% higher than the corresponding Day 1 values. The metabolite could not be detected in urine at any time in any patient. PQ and its metabolite did not show any accumulation in blood cells.

No abstract

No abstract

Apparently healthy Indian lactovegetarians have significantly lower serum levels and urinary excretion of vitamin B₁₂ as compared to non-vegetarians. The low levels of serum vitamin B₁₂ in lactovegetarians are not due to defective absorption but to low dietary intake of this vitamin. Inspite of considerably low serum vitamin B₁₂ values, the lactovegetarians have no apparent signs or symptoms of vitamin B₁₂ deficiency and their response to injected cyanocobalamin mixed with tracer radioactive B₁₂, as judged by urinary excretion pattern and liver uptake, was similar to that observed in non-vegetarians.