Issues for surgery
Risk of increased post-operative complications secondary to anaemia if omitted for prolonged period.
Risk of poor visualisation and subsequent abandonment of procedure if continued prior to colonoscopy.
Advice in the perioperative period
Elective surgery
Continue.
Except:
- Patients undergoing colonoscopy – stop oral iron a minimum of 5 days before colonoscopy, as it forms an adherent residue that interferes with mucosal visualiation. See also bowel cleansing agents.
- Patients receiving intravenous iron – stop oral iron for minimum of 5 days after intravenous iron administration.
For improved absorption and tolerability, review frequency of dosing – once daily or alternate day dosing is recommended – see Further information.
Pre-operative initiation
Screen for anaemia pre-operatively as early as possible in the patient’s pathway if surgery is anticipated to result in more than 500ml blood loss. Follow diagnostic algorithm in Centre of Perioperative Care (CPOC) Guidelines. For improved absorption and tolerability once daily or alternate day iron supplementation is recommended – see Further information.
Consider if commencing oral iron will impact on the absorption of existing medications (e.g., long term antimicrobials, levodopa, entacapone, levothyroxine); if so, counsel patient on the appropriate interval between oral iron and their other medication (consult British National Formulary).
Emergency surgery
Continue
Except:
- Patients receiving intravenous iron – stop oral iron for minimum of 5 days after intravenous iron administration.
Post-operative advice
Although it is possible to restart oral iron post-operatively when enteral intake resumes absorption is anticipated to be reduced in the initial post-operative period due to increased levels of the inflammatory protein hepcidin; therefore, consideration should be given to delaying the restart.
Post-operative initiation
Initiation of oral iron in the immediate post-operative period is unlikely to be beneficial as the post-operative inflammatory response releases hepcidin which reduces gastrointestinal absorption of iron; consider intravenous iron supplementation for patients with post-operative iron deficiency and/or moderate to severe post-operative anaemia; however, note that the current evidence base for this is weak.
Interactions with common anaesthetic agents
None.
Interactions with other common medicines used in the perioperative period
Antimicrobials
Fluoroquinolones
Oral iron is known to reduce the absorption of fluoroquinolones, e.g., ciprofloxacin, potentially leading to subtherapeutic levels and treatment failure. This is an established clinically significant interaction and administration of iron preparations and quinolones should be separated by at least 2 hours.
Tetracyclines
Oral iron is known to chelate with tetracyclines, e.g., doxycycline, reducing the absorption of both medicines and potentially leading to subtherapeutic levels and treatment failure. This is an established clinically significant interaction and administration of iron preparations and tetracyclines should be separated by at least 2-3 hours.
Proton pump inhibitors (PPIs)
Hypochlorhydria induced by PPIs (e.g., lansoprazole) may impair the absorption of iron from oral iron preparations. Although evidence for an interaction is limited, bear the reaction in mind should a patient taking PPIs fail to respond to oral iron therapy.
Further information
Oral iron dosing and the effect of hepcidin
Hepcidin is released in the presence of excessive iron replacement and reduces absorption of the next iron dose. Traditional multiple daily dose oral iron supplements are poorly absorbed and poorly tolerated due to diarrhoea and constipation (likely because of the continuing presence of unabsorbed iron in the gastro-intestinal tract). Once daily or alternate day dosing of iron supplements allow hepcidin levels to fall, maximising absorption and improving tolerability. An international consensus statement recommended a single daily dosing regimen of 40-60mg elemental iron, or an alternate day dosing regimen of 80-100mg elemental iron; pragmatically CPOC recommends a dose of either one tablet once a day or one-two tablets on alternate days.
References
Connor A, Tolan D, Hughes S et al. Consensus guidelines for the safe prescription and administration of oral bowel-cleansing agents. Gut (2012). Accessed via www.rcr.ac.uk 28th August 2022 Doi:10.1136/gutjnl-2011-300861
Joint Formulary Committee. British National Formulary (online) London: BMJ Group and Pharmaceutical Press. http://www.medicinescomplete.com [Accessed on 28th August 2022]
Centre for Perioperative Care. Guideline for the Management of Anaemia in the Perioperative Pathway (September 2022). Available at: https://cpoc.org.uk/guidelines-resources/guidelines [Accessed on 7th September 2022]
Munoz A, Acheson AG, Bisbe E et al. An international consensus statement on the management of postoperative anaemia after major surgical procedures. Anaesthesia 2018; 73(11):1418-1431 DOI: 10.1111/anae.14358
Summary of Product Characteristics – Sodium Feredetate 190mg/5ml Oral Solution. ADVANZ Pharma. Accessed via www.medicines.org.uk 28/08/2022 [date of revision of the text March 2019]
Baxter K, Preston CL (eds), Stockley’s Drug Interactions (online) London: Pharmaceutical Press. http://www.medicinescomplete.com [Accessed on 28th August 2022]
Munoz M, Acheson AG, Auerbach et al. International consensus statement on the peri-operative management of anaemia and iron deficiency. Anaesthesia 2017; 72(2): 233-247 doi:10.1111/anae.13773