Menatetrenone (INN), also known as menaquinone-4 (MK-4), is one of the nine forms of vitamin K2.
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Other names | 3-methyl-2-[(2Z,6E,10E)-3,7,11,15-tetramethylhexadeca-2,6,10,14-tetraenyl]naphthalene-1,4-dione |
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Routes of administration | By mouth |
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Bioavailability | Low (oral)[1] |
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Chemical and physical data | |
Formula | C31H40O2 |
Molar mass | 444.659 g·mol−1 |
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MK-4 is the major form of Vitamin K in vertebrate animals, including humans and common forms of meat animals. It is produced via conversion of vitamin K1 in the body, specifically in the testes, pancreas and arterial walls.[2] The conversion is not dependent on gut bacteria, occurring in germ-free rats[3][4] and in parenterally-administered K1 in rats.[5][6] Tissues that accumulate high amounts of MK-4 have a capacity to convert up to 90% of the available K1 into MK-4.[3][4][dubious ]
K1 is converted to MK-4 in three steps:[7]
The second and third steps are known to happen in target tissue. The first step is proposed to happen mainly in the intestines.[7]
Menatetrenone is approved in Japan for second-line treatment of postmenopausal osteoporosis. Evidence is restricted to small-scale RCTs; the minimum effective dose (for bone mass parameters) is 45 mg, much higher than the Daily Value for vitamin K (80 μg).[8]
420 μg of oral MK-4, in a single-dose or spread out over 7 days, does not cause detectable changes in serum MK-4 level in healthy women, whereas MK-7 produces the expected increases in MK-7 levels.[1]
The minimum effective oral dose to change serum osteocalcin levels is 1500 μg/d, where as oral MK-7 is effective on this parameter at 45 μg/d, a level more in line with nutritional intake. In addition, rat studies show that oral MK-7 is better at increasing extrahepatic tissue levels of MK-4 than oral MK-4.[1]
administered daily doses of 15, 45, 90, and 135 mg revealed that 45 mg was the minimum effective dose for improving bone mass parameters evaluated by microdensitometry and/or single photon absorptiometry in postmenopausal women with osteoporosis