This post is inspired by the confusion of intern year. Since our responsibility in the hospital has increased, the lens through which we interpret information has changed. For example, the pharmacology of opiates didn’t matter for Step I, Step II, or Step III. It used to be triaged to the bottom of the what-I-care-about list. But, now it matters when the well-educated patient comes in with nephrolithiasis, asking about pain medication options. How long will it last? When will she start to feel the effects/when will levels peak? This post will breakdown clinically relevant information about opiates–yes, pain is subjective so the daily utility of this may be of question. But, I felt it was my responsibility to at least know a little bit about what I prescribe. The good thing I’ve learned is that morphine and pain medication dosing hasn’t changed much in the past 20 years, so it’s knowledge I’m ok with memorizing.
Given that patients ideally don’t spend more than 24 hours in the Emergency Department, the first section of this post focuses on the acute effects of pain medication. The second portion consists of the Morphine Equivalent Daily Dose (MEDD). It translates the dose and route of the opiates the patient has received in the last 24 hours to an equivalent parenteral form of morphine. It’s less useful in the ED, but still valuable to be aware of the basics.
Dose – 0.1 mg/kg
Onset – 5-10 minutes
Peak – 30 minutes
Duration – 3-4 hours
Hydromorphone IV (Dilaudid) – about 5-10 times stronger than morphine IV
Dose – 0.2-1 mg q 2-3 hours
Onset – 5 minutes
Peak – 15-30 minutes
Duration – 3-4 hours
Fentanyl IV – about 100 times stronger than morphine IV
Dose – 1-2 mcg/kg. Note: this is for Fentanyl IV; below there is information on the conversion to Fentanyl patches.
Onset – immediate
Peak – 3-5 minutes
Duration – 0.5-1 hour
Morphine Equivalent Daily Dose
The Morphine Equivalent Daily Dose is a table to find the dose of morphine equivalent to another opioid over 24 hours.
The following example uses oral dosing:
If a patient is receiving 4 mg of Hydromorphone every 4 hours, what is the equivalent amount of morphine?
Notice on the table, the conversion factor for morphine to hydromorphone is 5. If a patient is receiving 4 mg of oral Hydromorphone every 4 hours, the patient is getting a total of 24 mg in 24 hours. Using a factor of 5, the oral morphine equivalent for that same time period is 120 mg.