Effects of menatetrenone on the bone and calcium metabolism in osteoporosis: A double-blind placebo-controlled study

Menatetrenone (2-methyl 1,3-tetraprenyl-1,4-naphtoquinone; vitamin K2) is a vitamin K homolog. To evaluate its efficacy on cortical bone mineral density and its safety, a 24-week double-blind placebo-controlled study was conducted by enrolling 80 osteoporotic patients. Patients were given either 90 mg/day of vitamin K2 (n = 39) or a placebo (n = 41). Bone density was assessed on the X-ray film of the right second metacarpal bone using the microdensitometric method. In the vitamin K2 group, bone density increased by 2.20% ± 2.48% from the baseline; in the placebo group, it decreased by −7.31% ± 3.65% (P = .037, K2vs placebo). Urinary excretion of γ-carboxyglutamic acid (Gla) significantly increased from 72.61 ± 4.08 nmole/mg creatinine before treatment to 88.36 ± 5.35 in the 24th week after completion of the vitamin K2 treatment (P = .008). In the placebo group, there were no significant changes in urinary Gla excretion. In the 24th week of the treatment, the urinary calcium/creatinine ratio in the vitamin K2 group decreased from 0.137 ± 0.018 to 0.118 ± 0.016; in the placebo group, it increased from 0.153 ± 0.018 to 0.189 ± 0.029. As a result, the 24-week levels in the vitamin K2 and placebo groups became significantly different (P = .028). There were a few adverse effects attributable to vitamin K2. Our findings suggest that vitamin K2 at a dosage of 90 mg/day is effective in maintaining peripheral cortical bone density and is safe in treatment for osteoporosis.