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Memo – shortage of supply
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Re: Transvasin Heat Rub Cream (applied to earlobe for capillary blood-gas testing)
Description of product affected
Transvasin Heat Rub Cream contains hexyl nicotinate 2% w/w, ethyl nicotinate 2% w/w and tetrahydrofurfuryl salicylate 14% w/w.1
Why we are providing this information
Due to problems with the availability of one of the active pharmaceutical ingredients (tetrahydrofurfuryl salicylate), Transvasin Heat Rub Cream will be out of stock until the end of 2015.
Background
Transvasin Heat Rub Cream is licensed for the relief of rheumatic and muscular pain and the symptoms of sprains and strains.1 It is also used off-label by the Home Oxygen Service Assessment Review teams when undertaking arterialised capillary blood gas testing in patients who may require oxygen, or those who are already receiving oxygen but have become acutely unwell, in order to determine whether they require hospitalisation. The cream is applied to the patients’ earlobe to dilate the capillaries so that a suitable blood sample can be obtained for analysis. Arterial blood-gas testing is considered a more accurate method for assessment of pO2, pCO2 and pH, although it is more invasive and not generally performed in community settings.
A meta-analysis of studies carried out in adults concluded that capillary blood is a clinically acceptable sample alternative to arterial blood if only acid-base parameters (pH and PaCO2) are of interest, but can be slightly less reliable for PaO2.2 Most studies that used the “arterialisation” of capillary blood method for obtaining samples used Algipan as a rubefacient, but this product has now been discontinued. The effectiveness of vasodilating agents in “arterialising” earlobe-capillary blood samples have not been formally assessed.2
Implications for patient care
There is no consensus on the role of capillary vs. arterial blood sampling. However, advocates of capillary blood sampling consider it less risky, less painful and similarly effective compared to arterial blood sampling. Some consider it a “fail-safe” technique to use clinically as the difference between arterial and arterialised blood gases decreases as absolute oxygen levels drop. Until resumption of stocks of Transvasin cream, an alternative topical preparation that can cause capillary dilatation is required.
Management options
Products containing topical analgesics in the form of salicylates, in addition to rubefacients (similar to Transvasin) have been identified in the table below.3,4 However, it must be stressed that their use would be off label, there have been no studies that have compared rubefacient properties of the various products, and it is unclear whether these alternative products will produce sufficient “arterialisation” of the capillaries to produce accurate results. No recommendations on use of a specific product can be made. As an alternative to rubefacients, there is some suggestion that using a hot flannel or a heating pad may produce the desired effect of vasodilatation. Good preparation of the ear (alcohol wipe, rubbing gently with gauze and rubefacients or heat) can usually encourage vasodilatation.
Rubefacients / Analgesic / Other / ManufacturerTransvasin / Hexyl Nicotinate 2% w/w and ethyl nicotinate 2% w/w / Tetrahydrofurfuryl salicylate 14% w/w / x / Thornton & Ross Ltd
Deep Heat Spray* / Methyl nicotinate / Ethyl salicylate 5%, hydroxyethyl salicylate 5% and methyl salicylate 1.0% / The Mentholatum Co Ltd
Dubalm cream / Ethyl nicotinate 1%, methyl nicotinate 1%, benzyl nicotinate 1%, / Glycol salicylate 2% / Capsicum oleoresin / Norma Chemicals Ltd
Currently out of stock, with a manufacturing delay of 3-4 months
Deep Heat rub‡ / x / Methyl salicylate 12.8% w/w / Menthol, eucalyptus oil, and turpentine oil / The Mentholatum Co Ltd
Deep Heat Max Strength‡ / X / Methyl salicylate 30% / Menthol / The Mentholatum Co Ltd
Balmosa cream‡ / X / Methyl salicylate 4% / Capsicum oleoresin, menthol, camphor / Galen Consumer Ltd
Currently out of stock, but should be back in stock by end of November/early December
Radian B Muscle Rub‡ / x / Methyl salicylate 0.42% / Capsicum oleoresin, menthol, camphor / Thornton & Ross Ltd
It should be noted that Finalgon, Fiery Jack, Algipan and Ralgex cream and spray are no longer available/ *To ensure local application only, the Deep Heat Spray is sprayed onto lint swab/cotton wool ball and applied to the earlobe/‡These products do not contain rubefacients, and therefore it is unclear whether they would produce adequate “arterialisation” of the capillaries.
References
1. Transvasin SPC (Date of revision = 31 July 2013): http://www.medicines.org.uk/emc/medicine/25417
2. Zavorsky G et al. Arterial versus capillary blood gases: a meta-analysis. Respir Physiology & Neurobiology 2007; 155: 268-279
3. Chemist+Druggist monthly pricelist November 2014
4. Chemist+Druggist guide to OTC medicines + diagnostics 45th edition – Autumn/winter 2014
Original document prepared by:
Hina Radia, London and South East Regional Medicines Information, Guy’s and St Thomas’ NHS Foundation Trust 12 November 2014.
Acknowledgements:
· Dr Brendan G Cooper, Consultant Clinical Scientist, Queen Elizabeth Hospital Birmingham, President, Association for Respiratory Technology and Physiology
· Samantha Prigmore, Respiratory Nurse Consultant, St. George’s Healthcare NHS Trust
· Claire Wood, Principal Respiratory Physiologist, Chest Unit, King's College Hospital
· Jo Hobbs, Physiotherapy Team Leader, Home Oxygen Service, Solent NHS Trust
· Graham Delves, Senior Associate – Home Oxygen, South East CSU
Document modified by:
Name of individual at other centre using the product with modifications, centre, date
For all correspondence please contact:
Name of person at base hospital where memo is circulated (i.e. NOT the original author at Guy’s and St Thomas’ NHS Foundation Trust
Disclaimer: The content of some of this memo is based on consensus opinion from clinical practitioners. Users should bear this in mind in deciding whether to base their policy on this document. As the products discussed in this memo would be used off-label, normal trust governance procedures would apply.