What is the difference between oral and intravenous (IV) dexamethasone?

From the Guidelines

Dexamethasone can be administered both orally and intravenously, with the oral route being preferred when possible due to its convenience, cost-effectiveness, and similar efficacy to IV administration. For most conditions, oral dexamethasone provides comparable bioavailability to IV administration, making it an appropriate first-line choice for patients who can take oral medications 1. Typical oral dosing ranges from 0.5-10 mg daily depending on the condition being treated.

Key Considerations

• IV dexamethasone should be reserved for patients who cannot take oral medications (due to vomiting, NPO status, or impaired consciousness), require rapid onset of action in emergency situations, or have severe conditions like cerebral edema or anaphylaxis.
• When converting from IV to oral dexamethasone, a 1:1 dose conversion is generally appropriate due to the high oral bioavailability.
• Both routes have similar side effect profiles including hyperglycemia, mood changes, insomnia, and increased infection risk.
• The primary advantage of IV administration is its immediate bioavailability and guaranteed delivery in critically ill patients, while oral administration offers greater convenience and reduced costs for outpatient management.

Administration Guidelines

• According to the American Society of Clinical Oncology clinical practice guideline update, dexamethasone can be administered orally or intravenously, with dosing depending on the emetic risk category of the chemotherapy regimen 1.
• For patients receiving highly emetic chemotherapy, the recommended dose of dexamethasone is 12 mg orally or IV on the day of chemotherapy, with 8 mg orally or IV on subsequent days.
• For patients receiving moderately emetic chemotherapy, the recommended dose of dexamethasone is 8 mg orally or IV on the day of chemotherapy, with 8 mg orally or IV on subsequent days.
• For low emetic risk, the dose is 8 mg oral or IV 1.

From the FDA Drug Label

When the intravenous route of administration is used, dosage usually should be the same as the oral dosage

• Key points:
  • The dosage for intravenous administration is usually the same as the oral dosage.
  • In certain situations, administration in dosages exceeding the usual dosages may be justified and may be in multiples of the oral dosages.
• The decision to use oral or intravenous dexamethasone should be based on the individual patient's needs and the specific clinical situation, considering factors such as the severity of the disease, the patient's response to treatment, and the potential for adverse reactions 2, 3.
• Main consideration: The choice between oral and intravenous dexamethasone should be guided by the principle of using the lowest effective dose and the most appropriate route of administration to achieve the desired therapeutic effect while minimizing the risk of adverse reactions.

From the Research

Dexamethasone Administration

• The study 4 compared the pharmacokinetics of oral vs. intravenous dexamethasone in patients hospitalized with community-acquired pneumonia, finding that oral administration is a practical and safer alternative to the intravenous route.
• The bioavailability of oral dexamethasone in patients hospitalized with pneumonia was found to be sufficient, making it an appropriate alternative for intravenous administration in these patients.

Hyperglycemia Associated with Dexamethasone

• The study 5 found that dexamethasone administration before brain ischemia resulted in a worsening of postischemic outcome that was related to drug-induced hyperglycemia.
• Restoration of normoglycemia using insulin resulted in a functional outcome similar to that in the control group, and an attenuation of dexamethasone-associated histologic injury.
• The study 6 investigated the effect of different types of oral or intravenous corticosteroids on capillary blood glucose levels in hospitalized inpatients with and without diabetes, finding that treatment with oral or IV dexamethasone or methylprednisolone was associated with greater hyperglycemia.
• The study 7 discussed the physiopathology and correct management of glucocorticoids-induced diabetes, referring to diabetic patients who have to take such drugs for long periods.
• The study 8 evaluated glycaemic profiles of COVID-19 patients without diabetes receiving dexamethasone and determined factors associated with hyperglycaemia, finding that half of subjects without diabetes experienced hyperglycaemia post-dexamethasone.

Comparison of Oral and IV Dexamethasone

• The study 4 found that the AUC ratio of 6 mg oral and 4 mg intravenous dexamethasone was 1.22, representing a bioavailability of 81% after correction for differences in dexamethasone dose.
• The study 8 found that BGs post-intravenous were higher than post-oral administration for the initial six hours.