An ideal route of drug administration is the route that yields sufficient serum levels to produce the desired effect of the drug with minimal undesired effects. There are several advantages to support the prompt switch from IV to oral therapy, some of which are:

  • Less costly
  • Saves both medical and nursing time
  • Patients are more likely to receive the medications at the correct time
  • Potential reduction of risk in terms of adverse effects and errors
  • Reduction of fear and discomfort to patient

Many patients in hospital continue to receive intravenous medications longer than necessary. Although intravenous medications may be more bioavailable and have greater effects, some oral drug preparations produce serum levels comparable to those of the intravenous form.

Considerations for IV to Oral Switch

The nurse, physician, pharmacist and in some cases even the patient can be good sources of information regarding the patient’s ability to tolerate oral medications. If the patient is taking other medications by mouth, this may be an indication that the patient can be eligible for an IV to oral switch.

After 24-48 hours of intravenous therapy, patients should be reviewed for consideration of IV to oral switch therapy. The criteria to determine appropriateness of switching from IV to oral therapy should include, but are not limited to, the following:

  • Observed clinical improvement
  • Clinical markers showing a trend towards normal
  • Oral route is not compromised
  • Intact and functioning gastrointestinal (GI) tract
  • Does not meet exclusion criteria
  • Specific indications for prolonged IV therapy (high-risk infections)

Pharmacokinetic and Pharmacodynamic Issues

Dosage formulations and bioavailability are the main pharmacokinetic parameters to be considered. Intravenous medications have a bioavailability of 100% because they are administered directly into the blood stream.

For oral medications, bioavailability may be less due to the variability in the rate and extent of dissolution of the oral dosage form and the total amount of the free drug absorbed into the systemic circulation taking into account other factors that might affect absorption, i.e. first pass effect.

The oral equivalent of an intravenous drug should possess pharmacokinetic properties that result in minimal disruption to the treatment course. The oral equivalent should have recognised benefits or an indication for the condition being treated and its use should be supported by evidence.

Exclusion Criteria

Listed are some criteria indicating that oral therapy may not be appropriate:

  • Existing nil by mouth (NPO/non per os) order
  • Nasogastric tube with continuous suction
  • Severe/persistent nausea and vomiting
  • GI transit time too short for absorption
  • Active GI bleeding
  • High doses of vasopressor medications
  • Difficulty swallowing or loss of consciousness and no nasogastric access available
  • Documented ileus or GI obstruction
  • Continuous tube feedings that cannot be interrupted which is incompatible
    with the medication


Switching medications from the IV to oral route results in direct cost reduction of not only the medicine but also the equipment used. Nursing time spent on the preparation, checking and administration of doses is also significantly reduced.

Two good examples that could be easily implemented in hospitals are paracetamol and proton pump inhibitors.

The analgesic efficacy of paracetamol is related to peak plasma concentrations. Since certain oral formulations of paracetamol achieve peak plasma concentrations close to those achieved with IV paracetamol, the IV formulation can only be justified in circumstances where the oral formulation cannot be given, i.e. significant/prolonged vomiting or enteral routes of therapy are unavailable.

The cost difference between IV and oral paracetamol preparations are more than one hundred fold. IV paracetamol consistently belongs to the top 20 pharmacy imprest cost drivers in private hospitals, especially surgical hospitals as protocols on IV to oral switch therapy are not common and the switch may not happen until the next medical or surgical review.

Aside from direct cost differences, administering oral paracetamol only requires one nurse for checking and administration and would normally take less than a minute to administer, whereas on the other hand, an IV dose needs two nurses for double checking and should be administered over a period of 15 minutes.

Need for Guidelines

An effective IV to oral switch program could result in over 70% reduction in IV paracetamol costs. It is well known that oral paracetamol is a lot cheaper and quicker to administer compared to IV paracetamol, but why do we still administer it for prolonged durations? Is it simply because of doctor’s orders not being changed? Nursing staff perception on the IV formulation being more superior in efficacy? Or is there also an uncertainty on when to recommend or query a step down to oral therapy?

Empowering nursing staff to assess the ongoing need for IV therapy is the most effective way of driving such a program in the private hospital setting. Setting up guidelines on how to assess the eligibility of a patient to switch to oral therapy would provide nursing staff with a tool to refer to before making that query with the prescribing doctor. Once guidelines are in place and tested, doctors could be encouraged to prescribe a select group of drugs as IV/O instead of IV. This empowers nursing staff to use their clinical judgment, supported by the guidelines, to assess the most ideal route of drug administration for the patient at the time of administration.

Table 1 provides a summary of common drugs that may be considered for IV to oral switch therapy. Due to the differences in bioavailability of each drug, dose difference between IV and oral formulations should be considered, and the pharmacy consulted for dosing advice.

Table 1. Bioavailability of drugs eligible for IV to oral switch therapy.

<50% 50-80% 80-100%
Aciclovir Ciprofloxacin Amoxycillin Linezolid
(well distributed into tissues)
Dexamethasone Clindamycin Moxifloxacin
Morphine Digoxin Esomeprazole Methylprednisolone
Ranitidine Metoprolol Fluconazole Metronidazole
Pantoprazole Hydrocortisone Paracetamol
Ketorolac Phenytoin
Levetiracetam Co-trimoxazole


  1. Rawlins MD, Henderson DB, HIjab AR. Pharmacokinetics of paracetamol (acetaminophen) after intravenous and oral administration. Eur J Clin Pharmacol 1977; 11: 283–286.
  2. Bristol Myers Squibb Pharmaceuticals. Perfalgan Australian Approved Product Information. 2004.
  3. NSW Therapeutic Advisory Group Inc., Paracetamol use: A position statement of the NSW Therapeutic Advisory Group Inc. December 2008.
  4. Teich JM, Petronzio AM, Gerner JR, et al. An information system to promote intravenous-to-oral medication conversion. Proc AMIA Symp. 1999; 415–9.
  5. Lacy CF, Armstrong LL, Goldman MP, et al., eds. Drug Information Handbook. 15th ed. Hudson, OH: Lexi-Comp; 2007.

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