In converting morphine from oral to intravenous, how much IV morphine is equivalent to 30 mg of oral morphine?

To determine the intravenous (IV) equivalent of oral morphine, it’s important to know the relative potency between the two routes of administration. Morphine undergoes significant first-pass metabolism when taken orally, which decreases its bioavailability. Generally, it is estimated that oral morphine is approximately three times less potent than IV morphine.

In this instance, if a patient is prescribed 30 mg of oral morphine, converting that dose to IV morphine involves dividing the oral dose by the estimated bioavailability factor. Given that oral morphine is roughly one-third as effective as IV morphine, you would take 30 mg and divide it by 3, resulting in an equivalent dose of 10 mg of IV morphine.

This conversion is critical for safely managing pain in patients requiring morphine, ensuring they receive an effective but appropriate dose regardless of the administration route. Choosing the right conversion factor is essential for patient safety and therapeutic efficacy.