Vitamin K1 in oral solution or tablets: a crossover trial and two randomized controlled trials to compare effects.

BACKGROUND: Vitamin K1 (VK1) reverses the effects of vitamin K antagonists (VKAs). The literature shows that the bioavailability from solutions might be higher than that from tablets, possibly resulting in different effects. OBJECTIVES: To compare the bioavailability and effect on the International Normalized Ratio (INR) of 5-mg VK1 tablets and solution in three randomized clinical trials. METHODS AND RESULTS: The bioavailability was determined in a crossover trial with 25 healthy volunteers. VK1 plasma concentrations were assessed at 0, 2, 4, 5, 6, 8, 10 and 24 h, and the area under the curve was higher in the solution group than in the tablet group (mean difference 365 µg L(-1) h, 95% confidence interval [CI] 230-501, P < 0.0001). In the other two trials, the effects of both formulations on the INR were measured at 0, 24 and 48 h. In the second trial, on 72 patients on phenprocoumon with planned invasive procedures, both formulations were similarly effective, because all patients reached an INR of < 2.0, which was the primary endpoint. In the last trial, on 72 patients on phenprocoumon with an INR of 7.0-11.0, the INR decreased slightly more in the solution group (4.7, 95% CI 4.3-5.1) than in the tablet group (4.2, 95% CI 3.8-4.6). The solution group had a 3.3-fold increased likelihood (95% CI 0.7-15.1) of reaching an INR of < 2.0 at 48 h. Additionally, the increases in VK1 concentrations were similar (tablets, 3.2 µg L(-1) ; solution, 3.4 µg L(-1) ; P = 0.99) after 24 h. CONCLUSIONS: VK1 tablets are at least as clinically effective as the solution in countering VKAs.

Heterophilic antibodies may be a cause of falsely low total IGF1 levels.

BACKGROUND: A low serum total IGF1 is considered as a diagnostic indicator of GH deficiency (GHD) in the presence of hypopituitarism. Introduction of IRMA and chemiluminescent immunometric assay (CLIA) IGF1 immunoassays has introduced endogenous antibodies as a new source of interference. In general, this goes unnoticed and might lead to unnecessary diagnostic and therapeutic interventions. CASE: A 56-year-old man was referred with a decline in physical performance, unexplained osteopenia, and weight loss of 3 kg over the past 8 months. Although clinical signs and symptoms were unremarkable, laboratory results pointed to secondary hypothyroidism and secondary hypogonadism. In addition, the serum total IGF1 level (CLIA; Siemens Medical Solutions Diagnostics) was in the low normal range. Two GH stimulation tests were performed, but these tests did not support the diagnosis GHD. Moreover, IGF1 bioactivity measured by the kinase receptor activation assay was normal. Interference of heterophilic antibodies was considered. After pretreatment with specific heterophilic blocking tubes that contain blocking reagents to eliminate heterophilic antibodies, serum-free thyroxine, testosterone, and IGF1 levels turned out to be normal. CONCLUSION: To the best of our knowledge, we here describe the first case in the literature of a patient with low serum total IGF1 levels due to interference from heterophilic antibodies in the used IGF1 immunoassay. When confronted with low-IGF1 levels that do not fit the clinical picture, interference of heterophilic antibodies should be considered in the differential diagnosis.

Determinants of increased angiotensin II levels in severe chronic heart failure patients despite ACE inhibition.

INTRODUCTION: The beneficial effects of ACE inhibitors are generally ascribed to blockade of neurohormonal activation. However, especially in chronic heart failure (CHF) patients plasma angiotensin II and aldosterone levels can be elevated despite ACE inhibition, the so-called ACE escape. In the present study, we aimed to identify the frequency and determinants of ACE escape in CHF patients. METHODS: We studied 99 stable chronic heart failure patients (NYHA class III and IV, 66% ischemic etiology) receiving long-term therapy with ACE inhibitors. In all patients, cardiac, renal, and neurohormonal parameters were measured. ACE escape was defined as plasma angiotensin level > or = 16 pmol/L. RESULTS: Mean (+/- SD) left ventricular ejection fraction of our 99 patients (79 men and 20 women, age 69 +/- 12 years) was 28 +/- 10%. In addition to an ACE inhibitor, 93% of patients received diuretics, 71% a beta-blocker, and 49% spironolactone. None of the patients used an angiotensin receptor blocker. In our population, 45% of the patients had an angiotensin II plasma concentration higher than 16 pmol/L (median concentration was 14.1 pmol/L). Spironolactone use was an independent predictor of elevated plasma angiotensin II levels. Furthermore, spironolactone users had significantly higher plasma active renin protein and aldosterone levels. Plasma angiotensin II concentration was positively correlated to active renin, plasma angiotensin I and plasma aldosterone. No correlation was found between plasma angiotensin II levels and serum ACE activity, dose of ACE inhibitor, or duration of use. CONCLUSION: In a group of severe chronic heart failure patients, 45% had elevated plasma angiotensin II levels independent of serum ACE activity despite long-term ACE inhibitor use. Although a causal link could not be proven, an association was found between spironolactone use and active renin protein, angiotensin II and aldosterone levels, suggesting that escape from ACE is mainly caused by a feedback mechanism.