Vitamin C Deficiency in Patients on Long-Term Deferasirox without Supplementation.

Background: Under conditions of iron overload, ascorbic acid is oxidised at an increased rate leading to a risk of vitamin C deficiency. With deferoxamine (DFO) standard therapy, vitamin C is usually given at a dose of 2–3mg/kg on the days of DFO infusion as this increases iron excretion by up to 30%. With deferarisox (DFX) chelation treatment, although supplementation is permitted, there is currently no information about the effects of vitamin C supplementation on iron excretion and it is often left to patients or their clinician’s discretion as to whether supplementation is given. With long-term treatment, in the absence of supplementation there is a potential risk that vitamin C deficiency will develop and this could influence response to treatment.

Patients and Methods: We have measured fasting plasma vitamin C in 41 patients who have been on long term deferasirox treatment for transfusional iron overload for between 1.5 and 5 years. 32 of these patients had received no supplementation and 9 patients had received 2–3 mg/kg/ day of supplementation. We have examined whether trends in serum ferritin, myocardial T2* and liver iron, during the final year of observation, relate to plasma levels of vitamin C.

Results: Fasting plasma Vitamin C was significantly lower in the 41 patients (mean=30.3μmol/l, SD=20.8) than healthy control patients (mean=60.29μmol/l SD=12.6) (P<0.0001). Fasting vitamin C levels were significantly lower in patients without supplementation (mean=26.1μmol/l, n=32) (p=0.011) than in patients who received regular supplementation (mean=45.5μmol/l, n=9). In the 32 patients without supplementation 23 (72%) had plasma levels less than two standard deviations from the control mean. Fasting vitamin C levels after a minimum of 1 year treatment without vitamin C supplementation negatively correlated with liver iron concentration as estimated by T2* MRI. One patient, who was subsequently found to have the lowest fating vitamin c level (2.9μmol/l) developed clinical signs consistent with scurvy with severe gum disease requiring dental clearance. We found no difference in the change of ferritin trend, LIC decrease or cT2* trend in the patients receiving supplementation from those who did not. We found that the correlation between LIC and serum ferritin was less clear in deficient patients (<36μmol/l or 2SD from the mean, r=0.51, p<0.01) than replete patients (>36μmol/l) (r=0.88, p<0.0001).

Conclusions: We conclude that with long-term deferasirox therapy without vitamin C supplementation, there is a significant risk of vitamin C deficiency with a potential for clinical scurvy. The risk of ascorbate deficiency is further increased at higher levels of body iron loading. These findings suggest that vitamin C supplementation (2–3mg/kg/day) should be recommended as standard for patients on long-term chelation therapy with deferasirox. It would also be of value to determine whether long term-response was improved by ascorbate supplementation.