Vitamin B12 Treatment Options: Supplementation vs. Intramuscular Injections

As a dietetic intern, I (AD) had the opportunity to present an inservice to family physicians and allied health professionals on vitamin B12 deficiency in the elderly during my placement at the Grandview Medical Centre Family Health Team (FHT). As I reviewed the literature, I became passionate about the importance of vitamin B12 deficiency diagnosis and treatment in light of the inconsistent diagnostic criteria and various treatment methods. As a result, I feel strongly that we need to raise awareness among health professionals on the need for more rigorous diagnostic criteria, as well as ‘non-traditional’ treatment methods such as oral supplementation versus intramuscular (IM) injections.

The main area of discussion during the inservice was the effectiveness of oral vitamin B12 supplementation compared to IM injections in light of the high prevalence of malabsorption due to the absence of intrinsic factor (IF) in people with pernicious anemia. IM injections have historically been the preferred treatment for vitamin B12 deficiency, bypassing the active absorption mechanism (where vitamin B12 binds to IF in the terminal ileum prior to absorption). However, the mechanism for absorption of vitamin B12 via the oral route is less commonly understood.

Oral vitamin B12 supplementation relies on free vitamin B12 to be absorbed passively without binding to IF. This accounts for 1–2% of total absorption and is unaffected in patients with pernicious anemia, gastro-duodenal surgical resection, and those with low gastric acidity (Cuskelly, Mooney and Young, 2007). Therefore, when pharmacological doses (>1,000μg) are ingested, approximately 1% of vitamin B12 (about 10 μg) is absorbed by passive diffusion exceeding the Dietary Reference Intake (DRI) requirement of 2.4μg/ day for all adults. Numerous randomized controlled trials have revealed oral vitamin B12 supplementation to be equally effective to IM injections for correcting cobalamin (B12) deficiency (Simone et al., 2005; Butler et al., 2006).

Diagnosis of Deficiency

Unfortunately, there remains no ‘gold standard’ diagnostic criteria of vitamin B12 deficiency. The most common measure for deficiency is serum B12, an unreliable and insensitive measure of vitamin B12 status (Gibson, 2005). Efforts are being made to raise the cutoff value for deficiency to effectively capture those with inadequate levels of cobalamin. For instance, at my FHT placement a serum cobalamin <130μg/l>

Because vitamin B12 deficiency is common and symptoms can be vague and similar to those experienced with aging (e.g., loss of appetite, fatigue, paleness and confusion), it can easily go undetected and untreated (Wolters, 2004). The danger of undetected vitamin B12 deficiency leading to mostly irreversible neurological and psychiatric implications emphasizes the importance of clinicians taking a closer look at vitamin B12 levels particularly among patients over the age of 50 years and those with other risk factors. Registered dietitians should recommend oral cobalamin

supplementation for those with low vitamin B12 status (<250μmol/l).

Benefits of Oral Supplementation

A Canadian cost analysis study reported a potential cost savings of $17.6 million per year by switching from IM injections to oral vitamin B12 therapy (van Walraven et al., 2001). Costs savings are attributed to decreased health care labour. Patient benefits of oral therapy include convenience of home therapy and decreased injection-related anxiety and discomfort.

People not suited for oral treatment are those unable to regularly take medications, those with short bowel syndrome, or those who have active bowel disease.

Conclusion

Following my inservice there is increased awareness at the FHT on vitamin B12 deficiency, the importance for more rigorous diagnostic criteria, and greater physician and dietitian confidence in recommending oral vitamin B12 supplementation. Reflecting on this rich learning experience has allowed me to truly appreciate the influence that research has on directing everyday practice.

I (AD) would like to thank my two preceptors, Michelle Saraiva, RD and April Hoover, RD, for their help and guidance in researching this topic and applying the evidence.

REFERENCES available from Michelle Saraiva.

Contact

Grandview Medical Centre Family Health Team
Cambridge, ON

Andrea D'Ambrosio, MAN, BASc
Masters of Applied Nutrition (MAN) Dietetic Intern
E: adambros@uoguelph.ca

Michelle Saravia, RD, MAN
E: msaraiva@gmchft.ca

April Hoover, RD, CDE
E: ahoover@gmcfht.caa