About This Conversion Tool

The Buprenorphine Conversion Calculator is a clinical support tool designed to assist healthcare professionals in estimating equivalent doses between various buprenorphine formulations and in planning for buprenorphine induction from other full agonist opioids. It accounts for differences in bioavailability and provides guidance based on established clinical guidelines.

Understanding the Outputs

The calculator has two distinct modes with different outputs:

• Buprenorphine to Buprenorphine: This mode calculates the equivalent daily dose across different formulations (e.g., Suboxone® film, Butrans® patch, Sublocade® injection). It presents the results in a table, highlighting the entered formulation for easy comparison. The output is based on the equivalent daily dose of sublingual buprenorphine.
• Other Opioid to Buprenorphine: This mode calculates the total daily Morphine Milligram Equivalent (MME) from one or more full agonist opioids. Based on the total MME, it provides a suggested initial induction dose of buprenorphine and displays a risk level (Low, Moderate, High) associated with the MME total, consistent with CDC guidelines.

How to Use the Calculator

Follow these steps depending on your conversion needs:

1. For Buprenorphine-to-Buprenorphine Conversion:
   • Select the “Buprenorphine to Buprenorphine” mode.
   • Choose the current buprenorphine formulation from the “Convert From” dropdown list.
   • Enter the patient’s current dose and select the correct dosing frequency (e.g., per day, per week).
   • Click “Calculate” to view a table of equivalent doses for other formulations.
2. For Opioid-to-Buprenorphine Induction:
   • Select the “Other Opioid to Buprenorphine” mode.
   • For each opioid the patient is taking, select the drug, enter the dose per administration, and choose the frequency.
   • If the patient is on multiple opioids, click “+ Add Another Opioid” to add more rows.
   • Click “Calculate” to see the total daily MME, risk level, and a recommended starting dose for buprenorphine induction.

Dosing Overview

Buprenorphine is a partial mu-opioid agonist with a ceiling effect on respiratory depression, making it a safer option for opioid use disorder (OUD) and pain management. However, its various formulations have significantly different bioavailabilities, requiring careful dose conversions.

• Sublingual (SL) Films/Tablets: These are the standard for dose equivalence, with a bioavailability of around 30%. Dosing is typically once daily.
• Buccal Films (Bunavail®): Have higher bioavailability than SL forms, meaning a lower milligram dose is needed for the same effect.
• Transdermal Patches (Butrans®): Provide continuous, low-dose buprenorphine over 7 days, primarily for chronic pain. Conversions are based on steady-state plasma concentrations.
• Extended-Release Injections (Sublocade®): A monthly subcutaneous injection for patients already stable on a transmucosal buprenorphine dose for at least 7 days. It provides steady medication levels throughout the month.

Switching and Induction

When converting a patient from a full agonist opioid (like morphine or oxycodone) to buprenorphine, the primary risk is precipitated withdrawal. This occurs because buprenorphine has a high affinity for the mu-opioid receptor and can displace full agonists, leading to a rapid onset of severe withdrawal symptoms.

To prevent this, the patient must be in a state of mild-to-moderate withdrawal before the first dose of buprenorphine is administered. The Clinical Opiate Withdrawal Scale (COWS) is commonly used to assess this. A waiting period is required after the last full agonist dose: typically 12-24 hours for short-acting opioids and 72 hours or more for long-acting opioids like methadone.

Managing a Missed Dose

Guidance for a missed dose varies by formulation and should be directed by a healthcare professional:

• Daily Formulations (SL films/tablets): If a dose is missed, the patient should take it as soon as they remember. If it is almost time for the next dose, they should skip the missed dose and resume their regular schedule. They should not take two doses at once.
• Weekly Patch (Butrans®): If a patch is forgotten, the patient should apply a new patch to a different skin site as soon as they remember and start a new 7-day cycle.
• Monthly Injection (Sublocade®): A missed injection appointment requires clinical consultation. There is a dosing window, but if too much time has passed, supplemental transmucosal buprenorphine may be needed before the next injection. The patient must contact their provider immediately.

Safety Alerts

• Precipitated Withdrawal: The most significant acute risk when starting buprenorphine. Ensure the patient is in adequate withdrawal before the first dose.
• Respiratory Depression: While buprenorphine has a ceiling effect, risk of severe respiratory depression increases significantly when combined with other CNS depressants, particularly benzodiazepines, alcohol, or sedatives.
• Hepatotoxicity: Cases of hepatic injury, including hepatitis and jaundice, have been observed. Liver function should be monitored, especially in patients with pre-existing impairment.
• QTc Prolongation: Transdermal buprenorphine (Butrans®) can prolong the QT interval, requiring caution in patients with risk factors for torsades de pointes.

Frequently Asked Questions (FAQ)

Why is the dose for Zubsolv® or Bunavail® different from Suboxone®?
Zubsolv® and Bunavail® have higher bioavailability than Suboxone® films or generic sublingual tablets. This means more of the drug is absorbed into the bloodstream, so a lower milligram strength is required to achieve the same clinical effect as a higher dose of Suboxone®.

How does the calculator convert the Butrans® patch dose?
The tool converts the patch’s delivery rate (in mcg/hour) to an equivalent total daily sublingual buprenorphine dose in milligrams. This conversion is based on pharmacokinetic studies comparing plasma concentrations between the two delivery methods.

What does the Sublocade® “Not Recommended” result mean?
Sublocade® is only approved for patients stable on a transmucosal buprenorphine dose between 8 mg and 24 mg per day. If the calculated sublingual equivalent dose falls outside this range, the calculator indicates that switching to a standard 100 mg or 300 mg Sublocade® dose is not recommended by the manufacturer.

Why does methadone have a variable MME conversion factor?
The MME conversion for methadone is non-linear and depends on the total daily dose. The conversion ratio is much higher at higher daily doses of methadone. The calculator uses a tiered system (e.g., 4x for <21mg/day, 8x for 21-40mg/day, etc.) as recommended by guidelines to reflect this complexity.

What is MME and why is it important for induction?
MME stands for Morphine Milligram Equivalent. It is a standardized value used to compare the potency of different opioids. Calculating the total daily MME helps clinicians assess overdose risk and determine an appropriate starting dose for buprenorphine induction, as higher MME values often require a more cautious approach.

Can I use this tool for patients on buprenorphine for chronic pain?
Yes, the conversion principles between different buprenorphine formulations are the same for both Opioid Use Disorder (OUD) and chronic pain indications. However, dosing strategies, target doses, and clinical goals may differ significantly. The opioid-to-buprenorphine induction mode is primarily based on OUD treatment protocols.

What is the COWS scale mentioned in the warning?
The Clinical Opiate Withdrawal Scale (COWS) is an 11-item checklist used by clinicians to objectively measure the severity of opiate withdrawal. A score is assigned based on signs and symptoms like resting pulse rate, sweating, pupil size, and anxiety. A score of 5-12 typically indicates mild withdrawal, which is the target state for safely initiating buprenorphine.

Does the calculator account for incomplete cross-tolerance?
No. The MME calculations are based on standard equianalgesic tables. When switching opioids, clinicians often reduce the calculated equianalgesic dose by 25-50% to account for incomplete cross-tolerance. This principle should still be applied with clinical judgment when interpreting the tool’s MME output and planning therapy.

References

1. Substance Abuse and Mental Health Services Administration (SAMHSA). TIP 63: Medications for Opioid Use Disorder. 2021.
2. The ASAM National Practice Guideline for the Treatment of Opioid Use Disorder: 2020 Focused Update. Journal of Addiction Medicine.
3. CDC Guideline for Prescribing Opioids for Chronic Pain — United States, 2016. MMWR Recomm Rep 2016;65(No. RR-1):1–49.
4. SUBLOCADE® (buprenorphine extended-release) injection, for subcutaneous use Prescribing Information. FDA.gov.
5. SUBOXONE® (buprenorphine and naloxone) sublingual film Prescribing Information. FDA.gov.
6. BUTRANS® (buprenorphine) transdermal system Prescribing Information. FDA.gov.