FOI release

Freedom of Information request on nitrofurantoin and hyponatraemia (FOI 21/799)

Published 29 December 2021

28th July 2021

FOI 21/799

Dear

Thank you for your email on 1st July requesting report details of the seven cases you identified of nitrofurantoin and hyponatraemia via the interactive Drug Analysis Profiles (iDAPs). The Yellow Card scheme has received an additional report since your email. Therefore, up to and including 25th July 2021, we have received 8 UK spontaneous ADR reports of nitrofurantoin and hyponatraemia.

For your data request, we have provided Category Ib data. Category Ib concerns a list of data fields, which exclude any information that can identify the patient and reporter and therefore can be released without the need for consideration from the Pharmacovigilance Expert Advisory Group (PEAG) under the FOI act. Please note that Category Ia data consists of anonymised aggregated adverse drug reaction (ADR) data in the format of iDAPs, which you have previously used.

Furthermore, please find enclosed three separate tables that summarise the information included in the 8 Yellow Card reports. Table 1a lists the following information:

• Drug ingredient
• Drug name as classified
• Dose
• Time to onset
• Route of administration
• Reaction
• Reaction outcome
• Patient medical history

Tables 1b and 1c provide a particular focus on the patients’ sex and age, respectively. We have provided these details in an aggregated format similar to the iDAPs. Please note, dose, time to onset, route of administration, reaction outcome, and patient medical history in table 1a are not mandatory fields in a Yellow Card report; reporters can submit a Yellow Card without providing this information. Therefore, please be aware, the columns with unknown indicate the reporter did not provide this information.

In your email, you mentioned the consultant was particularly interested in the severity of electrolyte disturbance, the time taken to recover and the patients’ ages. Unfortunately, only two reports provided the patient’s sodium levels. The lowest sodium level recorded was 114mmol/L, and the other result was 120mmol/L. The recovery time was provided in three of the four reports that confirmed the patient’s hyponatraemia resolved. In these reports, the recovery time ranged from one to nine days. Regarding the age of the patients, most were above 66 years old, as seen in table 1c. Similar to details given in table 1a, test results, recovery time and age are not mandatory information for healthcare professionals or patients to provide when completing Yellow Card reports.

When assessing the data provided within this response and on the iDAPs, it is important to note that a report of a suspected reaction to the Yellow Card scheme does not necessarily mean that the medicine or vaccine caused it, only that the reporter has a suspicion it may have. Therefore, not all events have been medically confirmed or diagnosed, as we encourage patients and healthcare professionals to report on the basis of suspicion alone. Reports submitted to MHRA may be due to concurrent diagnosed or undiagnosed illness, other medicines or purely coincidental events that would have occurred anyway in the absence of therapy.

Furthermore, the number of reports received should not be used to determine the incidence of a reaction as neither the total number of reactions occurring nor the number of patients receiving the drug is included in this data. Hence the data provided may not provide an accurate representation of what is occurring in the clinical setting. As such, please see the following link where you can search for the Summary of medicinal Product Characteristics (SmPC) for nitrofurantoin, which documents the recognised side effects of nitrofurantoin, with their associated frequencies: https://www.medicines.org.uk/emc/.

If you have not done so already, we encourage you to submit a Yellow Card report for the young patient mentioned in your email. Any emerging evidence relating to possible risks associated with medicines and vaccines is carefully reviewed, and, if appropriate, regulatory action would be taken.

I hope the information provided is helpful, but if you are dissatisfied with the handling of your request, you have the right to ask for an internal review. Internal review requests should be submitted within two months of this response’s date and can be addressed to this email address.

Yours sincerely,

FOI Team,

Vigilance and Risk Management of Medicines Division