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ISSUE/QUESTION: If a patient is allergic to shellfish, is it safe for them to consume

a) Calcium supplement derived from oyster shell (e.g. Teva pharm Calcium 500 mg (NPN = 80001408)

b) Glucosamine Sulfate derived from shrimp/crab exoskeleton (e.g. Webber Naturals Glucosamine Sulfate 500 mg capsules NPN =80000082)?

SUMMARY OF FINDINGS:

There are different kinds of shellfish and each kind contains different allergy-causing proteins [1].

Crustaceans: Crabs, lobster, crayfish, shrimp and prawn

Mollusks:

Bivalves: Clams, mussels, oysters and scallops

Gastropods: Limpets, periwinkles, snails (escargot) and abalone

Cephalopods: Squid, cuttlefish, octopus

Adverse reactions to shellfish can be either immunological or non-immunological and can be triggered by parasites, bacteria, viruses, marine toxins and biogenic amines (e.g. histamine) [2]. Some people can consume one type of shellfish but some others must avoid all shellfish [1].

Gluosamine Sulfate: Drug information center for Webber Naturals was contacted and the representative mentioned that the risk of anaphylactic reaction depends on sensitivity of the patient [3]. He further mentioned that according to their monograph it is almost 0 % and it is a judgement call [3]. The crab exoskeleton goes through numerous chemical modifications and purifications [3]. The representative forwarded the product monograph in an email which is quoted below:

The Glucosamine Sulfate ingredient is manufactured using a compound derived from the shells of crabs, shrimps, and prawns. Glucosamine Sulfate is a highly purified ingredient and does not contain allergenic shellfish flesh proteins. We are not aware of any allergic reactions to Glucosamine Sulfate in people with shellfish allergies. Our product monograph contains the following information:

 

Precautions / Cautions

Those allergic to shellfish have been concerned over a possible allergic reaction to glucosamine. Allergic reaction has not been reported as a practical concern, probably because the allergens are in the meat and the extraction process is able to denature any extraneous flesh protein. However, it must be recognized that individuals sometimes display profound sensitivity where it is not expected. If there is concern over possible allergic reaction, especially if anaphylactic reactions are possible, have the customer discuss the matter with their physician before commencing use [3].

Calcium Carbonate: The drug information center for Teva Pharm was contacted and the representative mentioned that allergy to shellfish stems from allergy to protein in the fish and oyster shells do not have any fish living in them for years and it goes through purification process making it highly unlikely to cause any allergy [4]. However, she advised to watch out the first time a patient consumes the product [4].

Upon doing a Google search I also found some information in the FAQ section of Os-Cal (Calcium + Vit D3).

Generally, when a person is allergic to shellfish, they are allergic to a protein in the fish. The oyster shells contained in Os-Cal are obtained by dredging only ancient oyster beds in offshore U.S. waters. These fossilized shells haven't had living oysters inside of them for thousands of years, and they are carefully ground to a powder, which is the source of calcium carbonate. The oyster shell powder is combined with pharmaceutical grade ingredients and subjected to rigorous testing for safety and tolerability. This helps make sure that the calcium carbonate is in a form that is readily ingested, disintegrated and metabolized by the human body. Since the source of calcium carbonate for Os-Cal Calcium + D3 and Os-Cal Extra D3 Caplets are taken from ancient oyster shell reefs and the shells are washed and oven-dried before being milled to supply the calcium, it is very unlikely that any of the protein allergens would be present [5].

BC Drug Poison & Information Center: The pharmacist at DPIC discussed different types of shellfish, types of allergies and found similar information to what is listed above. She added that no information was located in the references searched regarding case reports of allergic reactions from use of ground up oyster shells [6].

RECOMMENDATION / CONCLUSION:

Considering the information received from the two companies, online search and DPIC, it was concluded that the investigated products are safe to consume for someone with shellfish allergy, however type of allergy should be confirmed and caution should be taken the first time patient is exposed to the product in order to be safe.

References

1. . Shellfish allergy [Internet]. June 23, 2011 [cited 2012 Jan 5]. Available from:

2. Lopata AL, O'Hehir RE, Lehrer SB. Shellfish allergy. Clinical & Experimental Allergy. 2010; 40:850-858.

3. Nixon M. Webber Naturals Glucosamine Info [online]. E-mail to Rajwant Minhas (rajwant.minhas@fraserhealth.ca) 2012 Jan 5 [cited 2012 Jan 5].

4. In a conversation with Teva Pharm (Jan 5, 2012)

5. GlaxoSmith Kline. Os-Cal FAQs [Internet]. [cited 2012 Jan 5]. Available from: .

6. McInnes K. Shellfish allergy and calcium supplements [online]. E-mail to Rajwant Minhas (rajwant.minhas@fraserhealth.ca) 2012 Jan 5 [cited 2012 Jan 5].

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