Try to switch from IV-to-PO when possible

byMahitab Hany, BS Pharm, PGDipClinPharm, PGDipClinNutrition - last updated
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AS A HOSPITAL PHARMACIST, you should look for NEW opportunities for intavenous (IV) to oral (PO) conversions. Shortages of injectable medications will have more hospitals expanding their IV-to-PO protocols...

Most hospitals have oral conversions for medications such as quinolones and proton pump inhibitors (PPIs) to save costs, remove intravenous (IV) lines earlier, decrease workload, etc. But other IV-to-PO switches aren't as straight forward. See Table 1 for more details.

          ANTIMICROBIALS. Work with your infectious diseases physicians to create protocols when there's not an exact IV-to-PO conversion or culture results aren't available. Incorporate local resistance patterns. For example, consider changing ceftriaxone to cefdinir (Cefdin, Denrocef, Omnicef) or amoxicillin/clavulanate (Augmentin, Hibiotic, Amoclawin) once community-acquired pneumonia patients are hemodynamically stable and afebrile. Or switch from piperacillin/tazobactam (Tazocin, Inj-Pep, Pipra-Taz) to amoxicillin/clavulanate (Augmentin, Magnabiotic, Megamox) for an improving diabetic foot infection. But first ensure the patient doesn't have a risk of Pseudomonas.

ELECTROLYTES. Expect your PRN (when needed) replacement protocol for potassium to default to the oral instead of IV, unless patients are NPO (Nothing by Mouth), have poor absorption, hypokalemia symptoms, or severely low levels, such as less than 2.5 mEq/L. Also use oral (PO) magnesium or phosphorus for asymptomatic patients with mildly low levels especially during shortages of IV formulations. Save IV magnesium and phosphorus for larger doses due to increased side effects with oral products. For example, magnesium oxide 800 mg or more may increase diarrhea risk. Plus absorption of oral phosphorus supplements may be unreliable.

OPIOIDS. Create a protocol for post-operative or other acute pain patients. Consider changing PRN IV opioids to oral after several doses. For example, try oxycodone (Oxynorm) 5 mg PO or Tramadol (Ultram) 50 to 100 mg for morphine 2 to 4 mg IV.

Table (1). Considerations for IV-to-PO Conversions
Medication IV-to-PO Considerations Comments
Acetazolamide (Cidamex) Recommended doses for IV and immediate-release tabs are the same. NA
Amiodarone (Cordarone) < 1 week IV: switch to 800 to 1,600 mg/day PO.

1 to 3 weeks IV: switch to 600 to 800 mg/day PO.
> 3 weeks IV: switch to 400 mg/day PO.
 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. Amoxicillin has better GI absorption than PO ampicillin.
Ampicillin-sulbactam (Unictam) Convert to PO amoxicillin-clavulanic acid. Dose conversion will depend on indication. Ampicillin-sulbactam and amoxicillin–clavulanic acid have nearly identical spectrums of activity. NA
Azithromycin (Zithromax) 500 mg IV Q24H to 250 to 500 mg PO Q24H. NA
Bumetanide (Burinex) Dose and frequency of IV and PO bumetanide are the same. NA
Cefazolin (Zinol) Cefazolin 1 g IV Q8H to cephalexin 500 mg PO Q6H. NA
Ciprofloxacin (Ciprofar) 200 mg IV Q12H to 250 mg PO Q12H.
400 mg IV Q12H to 500 mg PO Q12H.
400 mg IV Q8H to 750 mg PO Q12H.		 NA
Clindamycin (Dalacin) Convert 600 mg IV Q8H to 300 to 450 mg PO Q6H to Q8H. Dose conversion will depend on indication.
Dexamethasone Doses of IV and PO dexamethasone are the same. Oral dexamethasone may be almost 90% bioavailable. Compared to IV, onset of oral is slower.
Diazepam (Neuril) Doses of IV and PO diazepam are similar. Oral diazepam is >90% bioavailable.3
Digoxin (Lanoxin) 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 (Altiazem) For an IV infusion rate of... Convert to PO dose of... Oral dose = (IV drip rate [mg/hr] x 3 + 3) x 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 (Vibramycin) Dose and frequency of IV and immediate-release PO doxycycline are the same. 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 (Nexium) Pharmacokinetics of IV and PO esomeprazole are similar. Bioavailability of oral esomeprazole is around 90% with repeated daily dosing.3
Famotidine (Antodine) Dose and frequency of IV and PO famotidine are the same. NA
Fluconazole (Diflucan) Dose and frequency of IV and PO fluconazole are the same. NA
Furosemide (Lasix) IV to PO conversion is ~1 mg IV to 2 mg PO. Bioavailability is ~50% for furosemide tablets and oral solution.12
Hydrocortisone (Solu-Cortef) Doses of IV and PO hydrocortisone are the same. 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.

Dose conversions are approximate. Titrate to response.
Hydralazine (Apresoline) Double the IV dose and administer orally, with monitoring for effect. NA
Labetalol (Labipress) Following IV treatment, start PO treatment with 200 mg PO x 1, 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 (Andovimpamide) Dose and frequency of IV and PO lacosamide are the same. NA
Levetiracetam (Keprra, Tiratam) Dose and frequency of IV and PO levetiracetam (immediate-release) are the same. NA
Levofloxacin (Tavanic) Dose and frequency of IV and PO levofloxacin are the same. NA
Levothyroxine (Euthyrox) The IV dose of levothyroxine is ~75% of the oral dose, assuming the patient has achieved euthyroidism. Bioavailability of oral levothyroxine is about 50% to 75%.
Linezolid (Averozolid) Dose and frequency of IV and PO linezolid are the same. NA
Lorazepam (Ativan) Doses of IV and PO lorazepam are the same. NA
Methylprednisolone (Solu-Medrol) Dose of IV and PO methylprednisolone are the same.

Methylprednisolone 4 mg is equivalent to prednisone or prednisolone
5 mg.		 Corticosteroid dose and dose frequency is determined by disease severity.
Metoprolol (Seloken Zoc) 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.

Divide daily doses of oral products as appropriate per formulation.
Metronidazole (Flagyl) 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.
Moxifloxacin (Avalox) Dose and frequency of IV and PO moxifloxacin are the same. NA
Pantoprazole (Controloc) Dose and frequency of IV and PO pantoprazole are the same. NA
Phenytoin (Ipanten) The total daily dose of IV and PO phenytoin are the same. Bioavailability of oral phenytoin capsules is 90% to 100%.

Divide daily doses of oral products as appropriate per formulation.
Rifampin Dosing recommendations for IV and PO rifampin are the same. NA
Trimethoprim-sulfamethoxazole (Septrin) Daily doses of IV and PO trimethoprim-sulfamethoxazole are the same. NA
Valproate sodium (Depakine) The total daily dose of IV valproate sodium and PO valproic acid (Depakine) are the same. Divide daily doses of oral products as appropriate per formulation.
Vitamin K (Konakion) Dose and frequency of IV and PO vitamin K are the same. NA
Voriconazole (Vfend) Convert 3 to 4 mg/kg IV Q12H to 200 mg PO Q12H. Adults who weigh less than 40 kg should get one-half the PO maintenance dose.

REFERENCES

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