A stabilizing effect found in Vitamin K
Tuesday, May 1, 2007
PTINR.com Staff
A U.S. study found unstable warfarin patients benefited from increased doses of vitamin K1
Following our April 2007 article highlighting a U.K. study that showed a benefit of dietary vitamin K1 to help unstable INR patients – a new study published in the February 2007 Journal of Thrombosis and Thrombolysis showed similar results.
The prospective study, out of the Department of Pharmacy, Chapel Hill, N.C. selected unstable patients and administered 500 micrograms of vitamin K during a 17 week evaluation period.
The small study population found 5 of the 9 patients (56%) demonstrating an improved time in range with INR decreases seen between 2-7 days after the administration of vitamin K1. A considerable variation in warfarin (Coumadin ®) dosing increase was required to improve INR control. “Unstable” was defined as variable INRs requiring a minimum of three dose changes or three INRs outside of therapeutic range within 6 months.
Patients evaluated their INRs at weekly intervals following training on the ProTime® monitor and INRatio® manufactured by ITC, Corp. and HemoSense respectively.
The patients were: mostly female (67%), average age of 50 and included patients with mechanical valve (33%), DVT (56%) and atrial fibrillation (11%).
The study demonstrated the following changes based on vitamin K1 dietary supplement:
The authors concluded, “INR fluctuations may decrease in selected patients with unstable INRs who receive vitamin K1 supplementation. A study with a larger sample size and longer follow-up period is needed. The results of the present study can help design such a study.”
Eight of the nine study participants elected to continue vitamin K1 supplementation following the study.
“Phylloquinone and menaquinone-4 have relatively short half-lives, 1-1.hours compared to menaquinone-7 with 72-96hours.” Dr. Ralph E. Holsworth, Director of Clinical and Scientific Research
Dr. Hosworth noted that use of menaquinone-7 begins to influence a warfarin INR in as little as 100 micrograms per day – one fifth the dose used in the Chapel Hill study. It is extremely important the type of vitamin K and the clearance of the supplement is understood before using. More frequent INR monitoring is recommended.
Supplement of vitamin K2 (MK-7), a dietary supplement is not recommended for any patients on warfarin.