By Jane Babin, Guest Columnist

Buprenorphine is the darling of the addiction treatment industry, rapidly replacing methadone as the "medication assisted treatment" of choice for opioid use disorder (OUD) and addiction.  

Unlike methadone, which can only be dispensed through an opioid treatment program, buprenorphine can be prescribed in the privacy of a physician's office and filled at a pharmacy.  As a class III controlled substance, prescriptions for buprenorphine can be phoned or faxed in, and scripts can be refilled up to 5 times in 6 months without a new prescription.

Class II controlled substances, like hydrocodone, oxycodone and morphine, require a new prescription each month and can neither be refilled nor phoned in.

The only federal limitations on prescribing buprenorphine for OUD is that a physician must complete mandatory education and treat only a limited number of patients (currently 275). 

Ironically, these restrictions do not apply when buprenorphine is prescribed off-label for pain, leading some physicians and patients to turn to buprenorphine for chronic pain as class II opioids become increasingly harder to get.

Yet without training on buprenorphine’s unique pharmacology and its implications, physicians treating chronic pain may be unaware of the risks it presents. Let me explain why.

Buprenorphine’s Effect on Other Opioids

Buprenorphine is an opioid that acts as an agonist of the mu opioid receptor (MOR), which causes pain relief, just like class II opioids.  It also has side effects similar to other opioids, including tolerance, dependence, abuse potential, constipation, sedation and potentially fatal respiratory depression. 

What distinguishes buprenorphine from other opioids is that it is only a partial MOR agonist (50%).  Thus the effects of buprenorphine -- both pain relief and the undesirable side effects – don’t exceed half that of other, full agonist opioids.

Buprenorphine also has a ceiling of maximum effectiveness that reaches a plateau as the dosage is increased. That ceiling is well below what can be obtained with morphine and other opioids, but the side effects can still lead to death in opioid-naïve patients.  Buprenorphine has a long plasma half life, binds very strongly to MOR, and remains bound for extended periods of time.  Its usefulness in treating OUD is believed to lie in these properties, because it activates MOR sufficiently to curb drug craving, but not enough to elicit the euphoric effects that can lead to addiction. 

When an opioid that has higher analgesic potency, but lower MOR affinity, such as morphine or heroin, is also administered, buprenorphine wins the battle to bind and remains bound to MOR.  It can displace both heroin and naloxone from MOR, but neither can displace buprenorphine.  Naloxone can be effective when co-administered with buprenorphine -- as it is in combination drugs such as Suboxone -- but not after the administration of buprenorphine. 

Buprenorphine is also a kappa opioid receptor antagonist, which is thought to further reduce euphoria and addictive reinforcement. That’s great for patients with OUD, because it helps them resist the temptation to abuse opioids, and dampens or eliminates the euphoric effect of heroin or other opioids should they relapse.  

Increasingly, buprenorphine is being advocated for chronic pain patients.  With no more "proof" of efficacy for treating chronic pain than any other opioid, it has emerged as a less objectionable opioid because it appears safer in the eyes of addiction treatment specialists, such as Dr. Andrew Kolodny, who object to full MOR agonists for chronic pain. 

Yet safety is in the eyes of the beholder.  Despite its decreased abuse potential, buprenorphine can still be abused and cause overdoses because the ceiling effect for respiratory depression does not apply universally, particularly to opioid-naïve patients and children. Buprenorphine has caused the death of at least one child from unintentional exposure. 

Buprenorphine should not be used as the first opioid prescribed for chronic pain.  Because it cannot achieve the full analgesic effects that other opioids can, there is significant risk of buprenorphine leaving pain undertreated or even untreated.  A chronic pain patient on long-term buprenorphine therapy who experiences acute or breakthrough pain may not be able to get relief by taking another opioid.  Even more disturbing is the lack of pain control in patients who need surgery, have an acute injury from trauma or an acute painful medical emergency.

Buprenorphine Injection

Recently Indivior, a spin-off of Reckitt Benckiser Pharmaceuticals (which makes Suboxone), submitted a New Drug Application to the Food and Drug Administration on a subcutaneous injection formulation of buprenorphine. 

A once-a-month injection would be a significant advance for opioid administration because it would significantly reduce the risk of diversion.  A patient could hardly be accused of giving away or selling a drug that is deposited in his body, or of taking an incorrect dose.  

For this reason alone, an opioid depot formulation for a chronic pain patient with monthly administration sounds very appealing.  It might eliminate the need for pain contracts, pill counts, urine drug testing, and other indignations chronic pain patients suffer every day.  Even if another medication was needed for breakthrough pain, and drug testing was deemed necessary, the depot formulation would provide a virtually indisputable level of medication that could serve as an "internal control" for test error.  Detecting the depot med at unexpected levels would alert the prescribing physician to the inaccuracy of the test rather than suggest misuse or abuse.

Nevertheless, buprenorphine is not the right opioid for once-a-month dosing.  In a 2015 paper, lead author Dr. Yury Khelemsky described a horrifying case that illustrates the dangers inherent in daily buprenorphine use.  In this case, a patient with a history of drug addiction who was being treated successfully with Suboxone suffered a broken neck that required emergency surgery.

During the procedure, the anesthetized patient began to move in response to surgical stimulation, i.e., due to pain.  Despite increasing the amount of two anesthetics, Propofol and Reminfentanil, the patient continued to move.  Only after receiving yet another drug (Ketamine) did the patient remain motionless during the delicate procedure.  During a subsequent back surgery following discontinuation of Suboxone and replacement with short-acting opioids, roughly half as much Propofol and Remifentanil provided adequate anesthesia without the addition of Ketamine. 

Khelemsky noted that as little as 8 mg Suboxone (one third of the daily dose the patient was receiving), blocks the activity of hydrocodone for up to five days, and recommended discontinuing buprenorphine at least 72 hours prior to elective surgery.  This is cold comfort to a patient requiring emergency surgery -- which could be anyone.  

An injectable depot formulation of buprenorphine would substantially increase the risk of severe and possibly untreatable pain in an emergency situation, since a depot, once injected, cannot simply be discontinued as a pill would be.  Indeed, surgery may be needed to remove the depot and halt continued administration, while existing amounts of long-acting buprenorphine in plasma may necessitate higher, riskier doses of anesthetic to surgically treat the acute injury -- all while risking inadequate pain treatment.

Inexplicably, the extensive prescribing information on a random sample of buprenorphine products contains no warnings to either patients or prescribers of the risk that pain relief from an acute medical condition, trauma or surgery may be inadequate, or that buprenorphine should be discontinued days or weeks before elective surgery. 

Ironically, one package insert warns that additional analgesia may be required during childbirth, yet it fails to warn of any other situation that may require analgesia, or how analgesia can be accomplished when considering the unique pharmacology of buprenorphine.  

This seems to reflect the mindset of Kolodny and others in the addiction treatment industry, who always seem to minimize the significance of even the most severe pain encountered by an individual when compared to the perceived societal consequences of addiction.  I wonder how many pain patients or addicts would choose such a long-acting opioid if they understood the possibility that their severe acute pain could not be controlled.

The FDA committee tasked with reviewing Indivior’s new drug application is taking public comments.  I urge anyone concerned about this new buprenorphine formulation, and the failure to warn of the possibility of untreatable acute pain when taking any buprenorphine product, to provide comments by clicking here.

Comments can be submitted through October 27, 2017.  If received by October 17, they will be provided to the committee, which is scheduled to meet on October 31.  Comments received after October 17 will be taken into consideration by the FDA. 

Jane Babin, PhD, is a molecular biologist and a biotechnology patent attorney in southern California.

The information in this column should not be considered as professional medical advice, diagnosis or treatment. It is for informational purposes only and represents the author’s opinions alone. It does not inherently express or reflect the views, opinions and/or positions of Pain News Network.