The conversion of IV to PO levothyroxine
The conversion of IV to PO levothyroxine doses depends on the bioavailability of the oral formulation compared to IV. Here are the key recommendations:
- **General Conversion Ratio**: The oral (PO) dose is typically **twice the IV dose** (1:2 ratio) due to reduced bioavailability of oral levothyroxine[1][6].
- **Alternative Guidance**: Some sources suggest that the IV dose should be **50-70% of the oral dose**, meaning the oral dose is approximately 1.5–2 times the IV dose[4][5].
- **Clinical Considerations**: Adjustments may be required based on individual patient factors, such as thyroid function tests and clinical response[4][7].
For example, if a patient is on 50 mcg IV daily, they would typically require 100 mcg PO daily. Always consult local protocols or an endocrinologist for specific cases.
Sources
[1] [PDF] Automatic IV to PO Conversion Protocol https://adsp.nm.org/uploads/1/4/3/0/143064172/iv_to_po_protocol_2016.pdf
[2] [PDF] Appendix I -Intravenous (IV) TO Oral (PO) Dose Conversion - Adults https://www.albertahealthservices.ca/assets/info/hp/phys/if-hp-phys-mini-bag-shortage-alert-appendix-i.pdf
[3] [PDF] August 2019 Policy Title: Pharmacist-Managed Intravenous to Oral ... https://med.stanford.edu/content/dam/sm/bugsanddrugs/documents/clinicalpathways/SHC-IV-to-PO-Interchange-Protocol.pdf
[4] [PDF] Intravenous Levothyroxine 200mcg/ml (L-Thyroxine SERB®) Dose ... https://www.bedsformulary.nhs.uk/docs/Intravenous%20Levothyroxine%20200mcg%20v2.pdf
[5] [PDF] MEMORANDUM - GGC Medicines https://ggcmedicines.org.uk/media/uploads/prescribing_resources/iv_levothyroxine_memo_v4_final_20191213.pdf
[6] [PDF] IV to PO Conversion - Nebraska Hospital Association https://www.nebraskahospitals.org/file_download/778e6b93-62b5-4bcf-9ea2-258c3c2a1ced
[7] [PDF] Use the steps below to assess patients for IV to PO conversion ... https://publicweb.novanthealth.org/Rx033_IV_to_PO_Conversion/IV_to_PO_Pharmacy_Conversion_021121.pdf
[8] [PDF] 202231Orig1s000 - accessdata.fda.gov https://www.accessdata.fda.gov/drugsatfda_docs/nda/2011/202231Orig1s000Sum.pdf