Medication Safety Bulletin February 2018 NSQHS Standard 4: Medication Safety
Low molecular weight heparins (LMWH) and new oral anticoagulants (NOACs): Caution when switching Anticoagulants were discussed in the April 2017 edition of this bulletin, however, incidents involving this class of drug, in particular NOACs, continue to occur. This edition will further highlight the main risks with NOACs to raise awareness and to promote safe practice at your site. Consider the following Australian incident: A 73 year old male patient was charted enoxaparin (Clexane®) 80mg twice daily for venous thromboembolism. Six days later rivaroxaban (Xarelto®) 15mg twice daily was prescribed on another drug chart. However, inadvertently, enoxaparin was not ceased. The patient received three concurrent doses of rivaroxaban with enoxaparin. The patient suffered a fatal cerebral bleed. Rivaroxaban is a NOAC which may be used as an alternative to warfarin in selected patients. Other NOACs include apixaban (Eliquis®) and dabigatran (Pradaxa®). Converting from injectable anticoagulant to NOAC# Converting from Converting to Instructions Subcutaneous LMWH or UFH
NOAC
Stop LMWH/subcut UFH then start NOAC when the next dose of LMWH or subcut UFH would have been due.
Continuous IV UFH infusion
NOAC
Stop IV UFH infusion and start NOAC immediately.
Practice points: •
Treatment overlap or bridging is NOT required when converting from injectable anticoagulant to NOAC or from NOAC to injectable anticoagulant.
•
Concomitant administration of NOAC with injectable anticoagulants is a major drug interaction that can result in serious bleeding or even death.
•
Before commencing a NOAC, ensure any existing anticoagulant order is clearly ceased on the medication chart. See example drug chart:
Unlike warfarin (36-72h until therapeutic INR), NOACs have a rapid onset of action of 30 minutes to 4 hours to full anticoagulant effect so an overlap with injectable anticoagulants, e.g. enoxaparin, dalteparin (Fragmin®), unfractionated heparin (UFH), is NOT required. Converting from NOAC to injectable anticoagulant# Converting from
Converting Instructions to
apixaban or rivaroxaban
LMWH or UFH
Stop NOAC then start LMWH/ UFH 12-24h after the last NOAC dose. Bolus dose of UFH not required.
dabigatran
LMWH
CrCl ≥ 30 mL/min: stop dabigatran then start LMWH 12-24h after last dabigatran dose.
(Conversion recommendation depends on renal function.)
CrCl < 30 mL/min: LMWH not recommended; dabigatran contraindicated. IV UFH
CrCl ≥ 30 mL/min: stop dabigatran then start UFH 12-24h after last dabigatran dose.* CrCl < 30 mL/min: stop dabigatran then start UFH 48h after the last dabigatran dose.* *Seek specialist advice regarding need for a bolus dose of UFH.
# Recommendations consolidated from Australian Clinical Guidelines. Local hospital guidelines may prevail over these recommendations.
Sulfonamide antibiotic allergy Whilst it is important to be vigilant for adverse drug reactions including drug allergies, it is equally important that the understanding and documentation of these is accurate so patients are not unnecessarily denied access to potentially useful therapeutic options. The term ‘sulfur (or sulphur, sulpha, sulfa) allergy’ is misleading and should not be used. Sulfur is an element which occurs throughout our body, and therefore it is not possible to be allergic to sulfur itself.
Drug group (examples of commonly Cross-reactivity used drugs) Sulfonamide antibiotics Allergic cross-reactivity • Sulfamethoxazole - used in within this group is combination with trimethoprim possible (Bactrim, Resprim, Septrin) • Sulfasalazine - a combination sulfapyridine (sulfonamide antibiotic) and a salicylate (Salazopyrin, Pyralin) • Sulfadiazine (Flamazine cream) Sulfonamide antiretrovirals • Fosamprenavir (Telzir)
Allergic cross-reactivity with sulfonamide antibiotics is likely on structural grounds but has not been established
Non-antibiotic sulfonamide drugs • Loop diuretics: furosemide (frusemide) (Lasix, Urex, Uremide) • Thiazide diuretics: hydrochlorothiazide (Dithiazide), chlortalidone (Hygroton) • Sulfonylureas: gliclazide (Diamicron, Glyade), glimepiride (Amaryl) • Celecoxib (Celebrex)
No relationship to sulfonamide antibiotic allergy
Sulfhydryl drugs • Captopril (Capoten) • Penicillin
No relationship to sulfonamide antibiotic allergy
Sulfate drugs • Morphine sulfate • Glucosamine sulfate
No relationship to sulfonamide antibiotic allergy
Sulfites, bisulfites, metabisulfites, sulfur dioxide • Sodium metabisulfite (contained in Epipen) • Sodium bisulfite (contained in Ferro-liquid)
No relationship to sulfonamide antibiotic allergy
When recording an allergic adverse reaction to medications, the specific name of the drug should be recorded and the nature of the reaction.
Patients who have had an allergic reaction to the combination of sulfamethoxazole and trimethoprim (Bactrim, Resprim or Septrim) should be considered potentially allergic to either trimethoprim (Alprim, Triprim) or sulfamethoxazole or both.
An allergy to a sulfonamide containing antibiotic does NOT necessarily imply, or increase the likelihood, of allergy to a non-antibiotic sulfonamide, other sulfur containing medicines nor sulfite preservatives. Cross-reactivity is unlikely because of their structural differences.
Contributions and feedback are most welcome – please email: PharmacyPractice@epicpharmacy.com.au
References are available on request