Opioid Analgesic Prescription Contributes to One-Third of OUDs in British Columbia

Bohdan Nosyk (Simon Fraser University)

A recent study found that over 32% of patients diagnosed with opioid use disorder (OUD) between 2001 and 2018 were prescribed non-cancer opioid analgesics prior to OUD diagnosis.

The proportion of opioid analgesic prescription prior to OUD peaked at 40% in 2011, but the percentage stabilized afterward and then declined.

Investigators, led by Bohdan Nosyk, PhD, of the BC Centre for Excellence in HIV/AIDS at St. Paul’s Hospital in Vancouver, said a link has been found between levels of opioid analgesic prescribing and mortality particularly in British Columbia (BC), Canada, where overdose rates are nearly 3 times higher than the national average.

Most overdoses in British Columbia had a history of long-term prescription opioid use but did not have an active prescription at the time of overdose, marking a transition to illicit opioid use.

Canada health experts recommend against the use of opioids for individuals with substance use disorders and doses exceeding 90 morphine milligram equivalents (MME/Day).

The team in the study aimed to characterize non-cancer opioid analgesic prescribing in British Columbia prior to OUD identification, as well as examining the extent of initial prescriptions concordant to current guidelines.

The Study

Investigators led a retrospective cohort study of a population-level linkage to define a cohort of individuals with OUD in British Columbia from January 1996 – September 2018.

Data was gathered using health records of 6 databases: PharmaNet, Discharge Abstract Database, Medical Services Plan, BC Vital Statistics, National Ambulatory Care Reporting System, and BC Corrections.

Individuals in the study were chosen based on who had accessed health services for OUD, but individuals who were diagnosed with cancer or had received palliative care were excluded from study.

Patients who initiated opioid analgesic therapy or identified with OUD between January 2001 and September 2018 were included in the study for 5 years of OUD identification data capturing.

The primary outcome of the study was initial observed opioid analgesic prescriptions. The doses of initial prescriptions in MME/day combined the product of drug strength per dose unit, number of units per day, and an MME conversion for comparison against different drug types.

Investigators identified 3 measures of initial analgesic prescriptions: high dose (≥90 MME/day), long-term (≥7 days), and concomitant sedative prescription.

The key exposure in the study was the source of prescription, with classifications by type of health system contact prior to initial prescription. These included inpatient-post discharge, non-inpatient acute or non-acute visit.

Sociodemographic and clinical characteristics such as age, sex, and substance use disorders were gathered to include key factors that may influence prescriptions, as well as other comorbid conditions.
Results

The cohort in the study included 66,372 individuals identified with OUD from 2001 – 2018, with 32.1% having an opioid analgesic prescription prior to OUD identification.

The proportion increased from 3% (n = 79) in 2001 to 41% (n = 1535) in 2011 and decreased to 32.2% (n = 1667) in 2018.

Individuals receiving prescriptions prior to OUD were older and had a higher prevalence of comorbid conditions. The proportion of males grew from 57.9% (n = 4847) to 64.5% (n = 2182).

Across all sources, the percentage of individuals receiving high dose (≥90

MME/day) initial prescriptions decreased from 15.7% (n = 1314) to 14.5% (n = 490).

Long-term (≥7 day) prescriptions decreased from 52.8% (n = 4419) to 43.8% (n = 1484), and concomitant sedative prescriptions decreased from 16.5% (n = 1378) to 10.8% (n = 365).

Over half of initial opioid prescriptions originated from non-acute care visits, with a peak of 56.8% in 2001. The proportion of prescriptions from inpatient visits increased from 19.7% in 2001 to over 28% at the end of the study in 2018.

The probability of receiving non-guideline prescriptions decreased for all 3 measures for inpatient and non-inpatient acute care, but remained stable for non-acute care.

Long-term prescriptions had the highest decrease measures, as inpatient visits decreased from 53.3% (95% CI, 50.9 - 55.8) in 2001 to 37.2% (95% CI, 33.9 - 40.5) in 2018.

Conclusions

Investigators concluded that although opioid analgesic prescription rates prior to OUD identification has declined since a peak in 2011, individuals identified with OUD in 2018 had previously received prescription opioid analgesics.

The team noted that current guidelines in opioid prescription may still need to adapt to reduce opioid use harms for patients and educate prescribers on the dangers.

“While understanding the causal contribution of opioid prescriptions to the rise in OUD prevalence in BC remains critical to evaluating current guidelines, evidence on the implications of opioid prescribing before and after OUD identification may be equally important in shaping policies to reduce opioid-related harms,” investigators wrote.

The study, “Opioid analgesic prescribing for opioid-naïve individuals prior to identification of opioid use disorder in British Columbia, Canada,” was published online in Addiction.