Dexamethasone Route - Why PO?

Although intravenous administration of dexamethasone is technically 100% bioavailable and bypasses first-pass metabolism, oral dosing remains the preferred route in most patients. This is because dexamethasone has excellent oral bioavailability (around 61-86%, Lexicomp), and the small loss from hepatic metabolism is not clinically significant.

Since its therapeutic effects, such as reducing airway inflammation, occur over several hours regardless of the route, the faster systemic delivery with IV does not provide a meaningful advantage in most situations.

Multiple RCTs show no clinically significant difference between oral and IV dexamethasone for relapse rates, admission rates, or symptom control. Moreover, oral administration is also less invasive, easier, and more comfortable for patients. This is especially true for our pediatric patients.

Time in hospital and riding in ambulances can be quite traumatizing for children, particularly the younger ages (in the range that would be affected by croup). There is good evidence that children rate needles as being the worst pain they experience in a health care setting and can lead to avoidance of seeking care when it is required. Supporting the use of oral Dexamethasone over IM form is in line with CHEO's (and other children's hospitals engaged in the program) comfort promise. It has the added benefit of causing less agitation in a patient with potentially severe upper airway obstruction that can be exacerbated by crying.

As with any treatment, it is best to start with the least invasive option. While intramuscular injection is a good alternative if oral is not feasible IV use is typically reserved for cases where vascular access is already indicated for other therapies.

For these reasons, the directives list PO as the preferred route, followed by IM, with IV reserved for patient in extremis.