Considerations for IV-to-PO Conversions

Full update May 2020

Converting patients from IV to oral meds has a number of benefits. For example, it can help reduce drug costs and workload for nurses and pharmacy staff, IV lines can be removed earlier, and it can possibly provide another option when an IV medication is in short supply. There are three different types of IV-to-PO conversions: sequential (replacing an IV med with its oral formulation), switching (replacing an IV med with an oral formulation that has the same effects), and step-down (replacing an IV med with an oral formulation that has similar effects).1,2,11 The following table lists considerations for IV-to-PO conversions of commonly used meds. Keep in mind, you’ll need to consider multiple factors when looking at the possibility of conversion (e.g., renal/hepatic dosing adjustments, indication, disease severity, etc). In addition, consider interactions between oral meds and enteral feeding (for more details see our commentary, A Stepwise Approach: Selecting Meds for Feeding Tube Administration).

Abbreviations: BID = twice daily; NA = not applicable; PO = oral; IV = intravenous

NOTE: Doses in this chart do not take into consideration adjustments for renal or liver dysfunction. Some of the dose conversions below are approximations. When appropriate, monitor and adjust PO dose as necessary.

Med

IV-to-PO Considerations

Comments

Acetazolamide

Recommended doses for IV and immediate-release tabs are the same.3

NA

Amiodarone

<1 week IV: switch to 800 to 1,600 mg/day PO.3

1 to 3 weeks IV: switch to 600 to 800 mg/day PO.3

>3 weeks IV: switch to 400 mg/day PO.3

Oral doses can be given once daily or divided BID if patients have GI intolerance.

Ampicillin

Convert to PO amoxicillin. Dose conversion will depend on indication. Ampicillin and amoxicillin have nearly identical spectrums of activity.4

Amoxicillin has better GI absorption than PO ampicillin.4

Ampicillin-sulbactam

Convert to PO amoxicillin-clavulanic acid. Dose conversion will depend on indication. Ampicillin-sulbactam and amoxicillin–clavulanic acid have nearly identical spectrums of activity.4

NA

Azithromycin

500 mg IV Q24H to 250 to 500 mg PO Q24H.5

NA

Bumetanide

Dose and frequency of IV and PO bumetanide are the same.3

NA

Cefazolin

Cefazolin 1 g IV Q8H to cephalexin 500 mg PO Q6H.5

NA

Ciprofloxacin

200 mg IV Q12H to 250 mg PO Q12H.3

400 mg IV Q12H to 500 mg PO Q12H.3

400 mg IV Q8H to 750 mg PO Q12H.3

NA

Clindamycin

Convert 600 mg IV Q8H to 300 to 450 mg PO Q6H to Q8H.6

Dose conversion will depend on indication.6

Dexamethasone

Doses of IV and PO dexamethasone are the same.3

Oral dexamethasone may be almost 90% bioavailable. Compared to IV, onset of oral is slower.3

Diazepam

Doses of IV and PO diazepam are similar.3

Oral diazepam is >90% bioavailable.3

Digoxin

50 mcg IV to 62.5 mcg (0.0625 mg) PO.

100 mcg IV to 125 mcg (0.125 mg) PO.

200 mcg IV to 250 mcg (0.25 mg) PO.

400 mcg IV to 500 mcg (0.5 mg) PO.

Digoxin oral tablets are 70% to 80% bioavailable.3

Diltiazem

For an IV infusion rate of:

Convert to PO dose of:10

Oral dose = (IV drip rate [mg/hr] x 3 + 3) x 10.10

Divide daily doses of oral products as appropriate per formulation.

3 mg/hr

120 mg/day

5 mg/hr

180 mg/day

7.5 mg/hr

260 mg/day

10 mg/hr

330 mg/day

15 mg/hr

480 mg/day

Doxycycline

Dose and frequency of IV and immediate-release PO doxycycline are the same.5

NA

Enalaprilat

For Hypertension:
Enalaprilat 1.25 mg IV Q6H to enalapril 5 mg/day PO.

Enalaprilat 0.625 mg IV Q6H to enalapril 2.5 mg/day PO.

Adjust initial PO dose based on blood pressure response.

Oral enalapril doses may be given once daily or divided twice daily.

Esomeprazole

Pharmacokinetics of IV and PO esomeprazole are similar.3

Bioavailability of oral esomeprazole is around 90% with repeated daily dosing.3

Famotidine

Dose and frequency of IV and PO famotidine are the same.5

NA

Fluconazole

Dose and frequency of IV and PO fluconazole are the same.5

NA

Furosemide

IV to PO conversion is ~1 mg IV to 2 mg PO.

Bioavailability is ~50% for furosemide tablets and oral solution.12

Hydrocortisone

Doses of IV and PO hydrocortisone are the same.7

Corticosteroid dose and dose frequency is determined by disease severity.

Hydromorphone

1.5 mg IV is equianalgesic to 6 to 7.5 mg of immediate-release PO.8

Dose conversions are approximate. Titrate to response.

See our chart, Equianalgesic Dosing of Opioids for Pain Management, for more details.

Hydralazine

Double the IV dose and administer orally, with monitoring for effect.3

NA

Isavuconazonium

Doses of IV and PO isavuconazonium are the same.3

NA

Labetalol

Following IV treatment, start PO treatment with 200 mg PO x1, then 200 or 400 mg PO 6 to 12 hours later depending on blood pressure response.

Titrate PO dose up to 1,200 mg Q12H if needed.

Administer an oral dose once blood pressure has started to increase following discontinuation of IV labetalol.

Lacosamide

Dose and frequency of IV and PO lacosamide are the same.3

NA

Levetiracetam

Dose and frequency of IV and PO levetiracetam (immediate-release) are the same.3

NA

Levofloxacin

Dose and frequency of IV and PO levofloxacin are the same.5

NA

Levothyroxine

The IV dose of levothyroxine is ~75% of the oral dose, assuming the patient has achieved euthyroidism.3

Bioavailability of oral levothyroxine is about 50% to 75%.3

Linezolid

Dose and frequency of IV and PO linezolid are the same.5

NA

Lorazepam

Doses of IV and PO lorazepam are the same.3

NA

Methylprednisolone

Dose of IV and PO methylprednisolone are the same.3

Methylprednisolone 4 mg is equivalent to prednisone or prednisolone
5 mg.3

Corticosteroid dose and dose frequency is determined by disease severity.

Metoprolol

Equivalent maximal beta-blocking effect may be achieved with IV and PO doses (mg) in a ratio of 1:2.5.

IV duration of action is less than with PO. Monitor and adjust dose as needed.9

Divide daily doses of oral products as appropriate per formulation.

Metronidazole

Dose and frequency of IV and PO metronidazole are the same.3

NA

Morphine

10 mg IV is equianalgesic to 30 mg PO.8

Dose conversions are approximate. Titrate to response.

See our chart, Equianalgesic Dosing of Opioids for Pain Management, for more details.

Moxifloxacin

Dose and frequency of IV and PO moxifloxacin are the same.5

NA

Pantoprazole

Dose and frequency of IV and PO pantoprazole are the same.5

NA

Phenytoin

The total daily dose of IV and PO phenytoin are the same.5

Bioavailability of oral phenytoin capsules is 90% to 100%.3

Divide daily doses of oral products as appropriate per formulation.

Rifampin

Dosing recommendations for IV and PO rifampin are the same.5

NA

Trimethoprim-sulfamethoxazole

Daily doses of IV and PO trimethoprim-sulfamethoxazole are the same.3

NA

Valproate sodium

The total daily dose of IV valproate sodium and PO valproic acid/divalproex products are the same.3

Divide daily doses of oral products as appropriate per formulation.

Vitamin K

Dose and frequency of IV and PO vitamin K are the same.3

NA

Voriconazole

Convert 3 to 4 mg/kg IV Q12H to 200 mg PO Q12H.3

Adults who weigh less than 40 kg should get one-half the PO maintenance dose.3

Information in the above chart is from the following U.S. product labeling, unless otherwise specified: Pacerone (November 2018); digoxin (October 2018); enalaprilat (October 2019); furosemide (November 2017); labetalol (December 2018); metoprolol (October 2019).

Project Leader in preparation of this clinical resource (360519): Stacy A. Hester, R.Ph., BCPS, Associate Editor

References

  1. Quap CW. Chapter 31. Intravenous to oral therapy. In: Murdaugh LB, Ed. Competence Assessment Tools for Health-System Pharmacies, 5th ed. American Society for Health-System Pharmacists, 2015.
  2. Wetzstein GA. Intravenous to oral (IV:PO) anti-infective conversion therapy. Cancer Control 2000;7:170-6.
  3. Clinical Pharmacology powered by ClinicalKey. Tampa (FL): Elsevier. 2020. http://www.clinicalkey.com. (Accessed April 29, 2020).
  4. Gilbert DN, Chambers HF, Saag MS, et al, Eds. Sanford Guide Web Edition. Sperryville, VA Antimicrobial Therapy, Inc., 2020. https://webedition.sanfordguide.com/en. (Accessed April 22, 2020).
  5. Cyriac JM, James E. Switch over from intravenous to oral therapy: a concise overview. J Pharmacol Pharmacother 2014;5:83-7.
  6. Johns Hopkins Medicine. Johns Hopkins ABX guide. Clindamycin. https://www.hopkinsguides.com/hopkins/view/Johns_Hopkins_ABX_Guide/540131/all/Clindamycin. (Accessed April 22, 2020).
  7. Clinical Resource, Corticosteroids: Selection, Tapering, and More. Pharmacist’s Letter/Prescriber’s Letter. March 2018.
  8. Clinical Resource, Equianalgesic Dosing of Opioids for Pain Management. Pharmacist’s Letter/Prescriber’s Letter. January 2020.
  9. Dasta JF, Boucher BA, Brophy GM, et al. Intravenous to oral conversion of antihypertensives: a toolkit for guideline development. Ann Pharmacother 2010.44:1430-47.
  10. UW Health. Atrial fibrillation – rate control drugs. March 20, 2019. https://www.uwhealth.org/cckm/cpg/cardiovascular/related/Atrial-Fibrillation-Mgt---Rate-Control-Drugs-190312.pdf. (Accessed April 30, 2020).
  11. Mazumder SA. Intravenous-to-oral switch therapy. July 30, 2018. https://emedicine.medscape.com/article/237521-overview#a2. (Accessed April 29, 2020).
  12. Ezekowitz JA, O’Meara E, McDonald MA, et al. 2017 comprehensive update of the Canadian Cardiovascular Society guidelines for the management of heart failure. Can J Cardiol 2017;33:1342-433.

Cite this document as follows: Clinical Resource, Considerations for IV to PO Conversions. Pharmacist’s Letter/Prescriber’s Letter. May 2020.

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