How many people in Canada use prescription opioids non-medically in general and street drug using populations?

Popova, Svetlana ; Patra, Jayadeep ; Mohapatra, Satya 等

In the past decade, the substantial rise in medical use of prescription opioids (PO) has been accompanied by a marked rise in non-medical use of these drugs in Canada (1) and the US. (2-5) In 2005, Canada ranked first in the world in per capita consumption of Hydromorphone, second for Morphine and Oxycodone, and third for Hydrocodone. (6) According to the International Narcotics Control Board, the diversion and abuse of opioid analgesics are increasing in Canada, although the exact extent of the problem is not known. (6) There are, however, some indications that the increased medical use of opioids has been accompanied by increased non-medical use of these drugs, coupled with increased levels of opioid dependence and overdose with consequent morbidity and mortality. (7-10) A recent cross-sectional US survey demonstrated that 13% of those who reported past-year non-medical PO use (about 1.3 million people) met criteria for PO abuse or dependence. (2) Moreover, in Ontario, Canada there were 20 fentanyl (a synthetic opioid analgesic)-related deaths in 2002, whereas in 2003 and 2004, there were 35 and 57, respectively. (10) In the United States, unintentional opioid analgesic poisonings increased more than 91% between 1999 and 2002. (11)

Canada lacks data on the number of non-medical users of POs; therefore, the present study aimed to estimate for Canada and the country's four most populous provinces--Alberta (AB), British Columbia (BC), Ontario (ON) and Quebec (QC)--for the year 2003: 1) the number, in the general population, of non-medical PO users, and 2) the number and trends, in the street drug using population, of: a) non-medical PO use, b) heroin use, and c) both non-medical PO use and heroin use.

METHODS

This study focused on the estimation of the numbers of non-medical PO users in either the general population or the street drug using population. The study did not examine any medical use, i.e., use of opioids exactly as prescribed regardless of whether the patient met the criteria of 'dependence' as defined by the Diagnostic and Statistical Manual of Mental Disorders. (12)

Number of non-medical PO users in the general population

There are no survey-based data of the number of non-medical PO users in the general population in Canada. Therefore, US data from different sources were used as a basis for estimates and projections for Canada for 2003.

The following US data were used:

1. Number of individuals who used POs non-medically in the past year (2004): 11.3 million; (13)

2. Estimated number of individuals who abuse heroin: 800,000; (14,15)

3. Number of individuals who received treatment for heroin abuse in 2003: 281,000. (16)

In order to extrapolate an approximate range of the number of non-medical PO users in the general population in Canada, the ratios for the US estimates of non-medical PO users to the number of heroin abusers (to estimate a lower limit) and to heroin abusers who received treatment (to estimate an upper limit) were determined. This resulted in ratio figures of 14.1:1 and 40.2:1, respectively. These US-based ratios were first adjusted by 1) the ratio of average consumption of narcotic drugs in Canada and US (12,545 DDD/ 29,500 DDD=42.5%, DDD= Daily Defined Doses) and then 2) by population, to estimate values for the 15-49 years age group, which scaled down the ratios to 3.8:1 and 10.9:1, respectively. Canadian and US average consumption of narcotic drugs for the years 2002-2004 were obtained from the INCB (17) (Table XIV http://www.incb.org/pdf/e/tr/nar/2005/narcotics_part4_tables.pdf).

To estimate the number of non-medical PO users in the general population for the 15-49 years age group, these ratios were multiplied by a recent estimate (based on the key informants survey (18) of Canadian illegal opioid users between 15-49 years) in order to determine a lower and an upper range of non-medical PO users in the general population in Canada. Lower and upper limit estimation was based on the assumption that the proportion of the heroin abusing population with or without treatment within the entire non-medical PO using population would be more or less similar in North America.

Number of regular illegal opioid and/or non-medical PO users among the street drug using population

Two complementary approaches were used for this estimation. The first approach (for methodology, see ref. 19) is based on the fact that the opioid-related overdose mortality rate tends to stay consistently between 1% and 2% per annum (see a meta-analysis (20,21)). Based on this assumption, we calculated back from overdose deaths to the street drug using population in Canada. It has been shown in the past that coroners' data give a more realistic picture of overdose deaths in Canada than the official mortality statistics of Statistics Canada, (22) which seem to miss a considerable portion of drug-attributable overdoses. Provincial chief coroners reported 958 overdose deaths (excluding suicidal cases) in Canada in 2002. Unfortunately, most of the Chief Coroners' reports did not have age/sex specifications for drug overdose. When these data were not available, we statistically estimated these distributions according to sex-age group distributions of Canada available from Statistics Canada. (23)

[FIGURE 1 OMITTED]

The second approach was based on a provincial key informants survey aimed to determine the prevalence of regular illegal opioid and/or non-medical PO users in Canada that was conducted between December 2003 and April 2004. Illegal opioid use was defined as the regular use of at least one type of opioid which was not medically prescribed to the user or not used as prescribed. The survey was sent to 35 select key informants in all provinces and territories of Canada who were requested to base their estimates on the best available provincial statistics. In total, 18 informants (5 ministerial officials, 4 field researchers, 7 drug addiction programme coordinators and 2 treatment consultants) sent back their completed questionnaires (for detailed methodology, see ref.18).

Distribution and trends of non-medical PO users, heroin users, and both in the street drug using population

The distribution and trends of usage of opioids were examined by using data from the multi-site Canadian OPICAN cohort. (24,25) This study assessed local samples of illegal opioid (and other) drug abusers in Vancouver, Edmonton, Toronto, Quebec City, Montreal, Fredericton and St. John's between 2002 (baseline) and 2005 (3rd follow-up), involving a sample of 585 participants. The main eligibility criteria for participation in the OPICAN cohort were: 1) having abused illegal opioids for a minimum of 1 year on the majority of days in the week, and 2) not having been in a drug treatment program in the previous 6 months.

Self-reported use in the past 30 days of the following POs was included: Demerol, Dilaudid, Methadone (illegal from street), Morphine, OxyContin, Percocet, and Tylenol 3 or 4.

To carry out the distribution of street opioid abuse by subgroups: POs-only, heroin-only, and combined POs and heroin, the proportions from the above three user types within the street drug using population of the OPICAN cohort estimates were applied to the midpoint estimate of the number of regular illegal opioid and/or non-medical PO users (based on provincial coroners' reports).

RESULTS

Number of non-medical PO users in the general population

It was estimated that in Canada there were between 321,000 to 914,000 non-medical PO users between the ages of 15 and 49 years in the year 2003. Among select provinces, British Columbia was found to have the highest rate of non-medical PO users per 100,000 population, followed by Alberta, Ontario and Quebec (Table 1).

Number of regular illegal opioid and/or non-medical PO users among the street drug using population

Based on coroners' data, it was estimated that within the street drug using population, there were between 48,000 and 96,000 (with a calculated midpoint of 72,000 persons) regular illegal opioid and/or non-medical PO users between the ages of 15 and 49 years in Canada in 2003 (Figure 1). There was only a small variation in the estimated population rates (Table 2).

Use of the second method based on the results of the key informants survey yielded similar results. Estimates for select provinces totalled more than 80,000 people with regular illegal opioid and/or non-medical PO use between the ages of 15 and 49 years in Canada (Table 2). The mean value was approximately 500 people per 100,000 population. Note that the final estimate was based on coroners' data (above), which was the more conservative estimate and also had more empirical support as compared to the subjective key informant estimates.

Based on proportions from the OPICAN cohort (non-medical PO users 48.9%; heroin users 27.8%; and combined non-medical PO and heroin users 23.2%), and applying these proportions with a midpoint estimate of number of regular illegal opioid and/or non-medical PO users of 71,850 (based on provincial coroners' reports; Table 2), it was estimated that more individuals used non-medical POs (35,000) than heroin (20,000) or the combination of the two (17,000) in Canada in 2003 (Figure 1).

Heroin use was highly prevalent in the large cities of Vancouver (71%) and Montreal (48%) while the non-medical PO use was highly prevalent among the respondents in three other cities, Edmonton (89%), Quebec City (88%) and Toronto (75%). The highest proportion of combined heroin and non-medical PO use was found among respondents in Montreal (37%), followed by Toronto (24%), Vancouver (22%), Quebec City (12%), and Edmonton (11%) (Figure 2).

Trends of non-medical PO users, heroin users, and both in the street drug using population

Data from the OPICAN survey showed that between 2002 and 2005 in Canada, there was an overall increase of 24.3% in the proportion of respondents who used non-medical POs only, with a 6.5% and 7.5% decrease in the proportion of heroin only users and combined non-medical PO and heroin users, respectively (all statistics were significant at p<0.001) (Table 3).

The highest relative increase non-medical PO only use was observed among respondents in Edmonton (23.9%, p<0.05). The relative proportion of heroin only use decreased significantly among respondents in both Montreal (13.9%, p<0.05) and Vancouver (14.8%, p<0.05).

DISCUSSION

This study has several limitations. First, the validity of the estimates depends on various assumptions. For example, the estimation of non-medical PO use in the general population in Canada was based in part on US data. In addition, the lower and upper limit estimation was based on the assumption that the proportion of the heroin abusing population with or without treatment within the entire non-medical PO using population would be more or less similar in North America.

Furthermore, the OPICAN data were obtained by self-report, a method subject to potential biases, though widely noted to be relatively accurate, even on sensitive topics such as drug use. (26,27) The data from key informants might also be subjective and biased with their own impressions or influenced by personal relationship between informants and researcher. (28,29)

This study estimated that in Canada in 2003, among the general population, there were between 321,000 to 914,000 non-medical PO users and, among the street drug using population, there were about 72,000 non-medical PO users, heroin users or both. Important information is lacking on the proportion of individuals who use these drugs regularly for non-medical use, and what proportion qualifies for dependence. However, even if only a small minority of the non-medical prescription users are dependent, this number would match the street drug abusers.

There are more non-medical PO users than heroin users today because of the apparent ease of acquiring these pharmaceuticals. Thus, the stereotype of the "addict" is changing into a broader definition affecting a larger part of our society.

Based on the observed increase in the population of PO users in the recent past in Canada, survey research is urgently needed to determine, as accurately as possible, the extent and patterns of non-medical PO use and identify those populations most at risk for abusing POs. In addition, in-depth studies need to be carried out that address the leaking out of prescription drugs from the medical system into illegal drug markets and finding ways to reduce such leakage. The next important step is to develop appropriate prevention programs without undermining access to pain treatment.

In addition, there are several strategies that come to mind which aim to prevent prescription drug abuse and need to be urgently implemented in Canada. These include: prescription drug monitoring programs, reduction of improper prescribing practices, education at all levels (including physicians, pharmacists, and the public), elimination of internet drug pharmacies, provision of warning labels on all controlled substance prescriptions, and development of non-opioid treatment of chronic pain.

Received: March 11, 2008

Accepted: September 25, 2008

REFERENCES

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(3.) Compton W, Volkow N. Major increases in opioid analgesic abuse in the United States: Concerns and strategies. Drug Alcohol Depend 2006;81:103-7.

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(5.) Zancy J, Bigelow G, Compton P, Foley K, Iguchi M, Sannerud C. College on problems of drug dependence taskforce on prescription opioid non-medical use and abuse: Position statement. Drug Alcohol Depend 2003;69:215-32.

(6.) International Narcotics Control Board (INCB). Report of the International Narcotics Control Board for 2005. Vienna, Austria, 2006.

(7.) Compton WM, Volkow ND. Abuse of prescription drugs and the risk of addiction. Drug Alcohol Depend 2006;83(Suppl 1):S4-S7.

(8.) Haydon E, Rehm J, Fischer B, Monga N, Adlaf E. Prescription drug abuse in Canada and the diversion of prescription drugs into the illicit drug market. Can J Public Health 2005;96(6):459-61.

(9.) Manchikanti L. Prescription drug abuse: What is being done to address this new drug epidemic? Pain Physician 2006;9:287-321.

(10.) Martin TL, Woodall KL, McLellan BA. Fentanyl-related deaths in Ontario, Canada: Toxicological findings and circumstances of death in 112 cases (2002-2004). J Anal Toxicol 2006;30:603-10.

(11.) Paulozzi L, Budnitz D, Xi Y. Increasing deaths from opioid analgesics in the United States. Pharmacoepidemiol Drug Saf 2006;15(9):618-27.

(12.) American Psychiatric Association. Diagnostic and Statistical Manual of Mental Disorders, 4th edition, Primary Care. Washington, DC: American Psychiatric Association, 2000.

(13.) SAMHSA. Prevalence and recent trends in misuse of prescription drugs. U.S. Department of Health and Human Services, SAMHSA, Office of Applied Studies, National Survey on Drug Use and Health, 2002, 2003, and 2004. 2006.

(14.) ONDCP. Policy paper: Opioid agonist treatment. Washington, DC: Office of National Drug Control Policy (ONDCP), 1999.

(15.) Rubinkam M. Heroin addicts clamor for scarce medicine. Washington Post, April 28, 2005.

(16.) NIDA. Research report series, National Institute on Drug Abuse. Baltimore, MD: NIDA, 2005.

(17.) International Narcotics Control Board. Report of the International Narcotics Control Board for 2005. Vienna, Austria, 2005.

(18.) Popova S, Rehm J, Fischer B. An overview of illegal opioid use and health services utilization in Canada. Public Health 2006;120(4):320-28.

(19.) Fischer B, Rehm J. The case for a heroin substitution treatment trial in Canada. Can J Public Health 1997;88:367-70.

(20.) Rehm J. Modes de consommation et repartition des drogues en Suisse. In: Fahrenkrug H, Rehm J, Muller R (Eds.), Drogues illegales en Suisse 1990-1993. La situation dans les cantons et en Suisse. Zurich: Seismo, 1995;13-34.

(21.) WHO. The World Health Report 2002: Reducing risks, promoting healthy life. Geneva: WHO, 2002.

(22.) Single E, Rehm J, Robson L, Van Truong M. The relative risks and aetiologic fractions of different causes of death and disease attributable to alcohol, tobacco and illicit drug use in Canada. CMAJ 2000;162(12):1669-75.

(23.) Rehm J, Baliunas D, Brochu S, Fischer B, Gnam W, Patra J, et al. The costs of substance abuse in Canada 2002. Ottawa, ON: Canadian Centre on Substance Abuse, 2006.

(24.) Fischer B, Rehm J, Brissette S, Brochu S, Bruneau J, El-Guebaly N, et al. Illicit opioid use in Canada: Comparing social, health and drug use characteristics of untreated users in five cities (OPICAN study). J Urban Health 2005;82(2):250-66.

(25.) Fischer B, Manzoni P, Rehm J. Comparing injecting and non-injecting illicit opioid users in a multi-site Canadian sample (OPICAN cohort). Eur Addict Res 2006;12(4):230-39.

(26.) Bonin J, Fournier L, Blais R, Perreault M, White N. Are the responses of clients with psychiatric and addiction disorders using services for the homeless valid? Can J Psychiatry 2007;52(12):798-802.

(27.) Darke S. Self-report among injecting drug users: A review. Drug Alcohol Depend 1998;51:253-63.

(28.) Gilchrist VJ. Key informant interviews. In: Crabtree BF, Miller WL (Eds.), Doing Qualitative Research. Thousand Oaks, CA: Sage Publications, 1992.

(29.) Marshall MN. The key informant technique. Family Practice 1996;13:92-97.

Svetlana Popova, MD, PhD, [1-3] Jayadeep Patra, PhD, [1,4] Satya Mohapatra, PhD, [1] Benedikt Fischer, PhD, [1,2,5] Jurgen Rehm, PhD [1,2,6,7]

Author Affiliations

[1.] Centre for Addiction and Mental Health, Toronto, ON

[2.] Department of Public Health Sciences, University of Toronto, Toronto, ON

[3.] Faculty of Social Work, University of Toronto, Toronto, ON

[4.] Department of Human Development and Applied Psychology, University of Toronto, Toronto, ON

[5.] Centre for Addictions Research of British Columbia, University of Victoria, Victoria, BC

[6.] Addiction Research Institute, Zurich, Switzerland

[7.] Epidemiological Research Unit, Clinical Psychology and Psychotherapy, Technische Universitat Dresden, Germany

Correspondence: S. Popova, Centre for Addiction and Mental Health, 33 Russell Street, Room T510, Toronto, ON M5S 2S1, Tel: 416-535-8501, ext. 4558, Fax: 416260-4156, E-mail: lana_popova@camh.net

Acknowledgements: This study was supported in part by funding from the Canadian Institutes of Health Research. This contribution was also based on research within the framework of the Second Canadian Study on Social Costs of Substance Abuse, which has received funding from the Canadian Centre on Substance Abuse. In addition, the current study was also in part financially supported by a contract of Schering-Plough Canada to the Centre for Addiction and Mental Health. The authors would also like to thank Sandy Maksimowska and Dolly Baliunas for their thorough review of an earlier version of this manuscript.

Table 1. Number of Non-medical PO Users among the General Population
in Select Provinces and Canada 2003 (15-49 years) Based on US Data

Provinces    Population       Regular Illegal      Non-medical
                              Opioid and/or        PO Users
                              Non-medical          (lower limit)
                              PO Users *            [dagger]

Alberta        1,726,518            10,000               38,307
British        2,142,038            20,000               76,613
Columbia
Ontario        6,366,193            30,000              114,920
Quebec         3,814,456            10,000               38,307
Canada         16,372,157           83,800              321,009

Provinces    Non-medical      Non-medical PO       Non-medical PO
             PO Users         Users (lower         Users (upper
             (upper limit)    limit) per 100,000   limit) per 100,000
             [dagger]         Population           Population

Alberta         109,058              2219                 6317
British         218,116              3577                10,183
Columbia
Ontario         327,174              1805                 5139
Quebec          109,058              1004                 2859
Canada          913,905              1961                 5582

* Based on provincial key informant data (18)
[dagger] Based on the US data (see methodology)

Table 2. Number of People with Regular Illegal Opioid and-or Non-
medical PO Use among the Street Drug Using Population in Select
Provinces and Canada (15-49 years of age), 2002-2003

                                  AB

                      M            F          Total            M

Population of      817,585        801,510    1,619,095      989,575
Canada

Number of               74             22           96           96
overdose
deaths *

Lower estimate        3710           1100            4810       4790
(number of
regular illegal
opioid and/or
non-medical
PO users) *

Upper estimate       7410         2210            9620         9570
(number of
regular
illegal
opioid and/or
non-medical
PO users) *

Midpoint             5560         1655            7215         7180
estimate
(number of
regular illegal
opioid and/or
non-medical
PO users) *

Midpoint             680          206              446          726
estimate
per 100,000
population *

Total                6660         3330          10,000       13,320
number of
regular
illegal
opioid and/or
non-medical PO
users [dagger]

Number of            2622         1124            3745          490
non-medical
PO-only users
[double dagger]

Number of               0            0              -          9072
heroin-only
users
[double dagger]

Number of            571          245              816         2547
non-medical PO
and heroin
users
[double dagger]

Total number of      3193         1368            4561       12,109
non-medical PO,
heroin  users
and both
[double dagger]

                      BC                                    ON

                      F          Total          M            F

Population of      1,014,450    2,004,025    2,898,570    2,966,410
 Canada

Number of                 29          125          275           85
overdose
deaths *

Lower estimate          1480         6250       13,750         4270
(number of
regular illegal
opioid and/or
non-medical
PO users) *

Upper estimate          2950       12,500       27,500         8500
(number of
regular
illegal
opioid and/or
non-medical
PO users) *

Midpoint                2215         9375       20,625         6385
estimate
(number of
regular illegal
opioid and/or
non-medical
PO users) *

Midpoint                 218          468          712          215
estimate
per 100,000
population *

Total                   6660       20,000       19,980         9990
number of
regular
illegal
opioid and/or
non-medical PO
users [dagger]

Number of                210          700         6713         2877
non-medical
PO-only users
[double dagger]

Number of               3888       12,960          154           66
heroin-only
users
[double dagger]

Number of               1091         3638         3689         1581
non-medical PO
and heroin
users
[double dagger]

Total number of         5189       17,298       10,556         4524
non-medical PO,
heroin  users
and both
[double dagger]
                                               QC

                    Total          M            F          Total

Population of      5,864,980    1,848,070    1,850,890    3,698,960
 Canada

Number of                360          179           55          234
overdose
deaths *

Lower estimate        18,000         8970         2750       11,720
(number of
regular illegal
opioid and/or
non-medical
PO users) *


Upper estimate        36,000       17,940         5510       23,440
(number of
regular
illegal
opioid and/or
non-medical
PO users) *

Midpoint              27,000       13,455         4130       17,580
estimate
(number of
regular illegal
opioid and/or
non-medical
PO users) *

Midpoint                 460          728          223          475
estimate
per 100,000
population *

Total                 30,000         6660         3330       10,000
number of
regular
illegal
opioid and/or
non-medical PO
users [dagger]

Number of               9590         3259         1397         4655
non-medical
PO-only users
[double dagger]

Number of                220         4774         2046         6820
heroin-only
users
[double dagger]

Number of               5270         3975         1703         5678
non-medical PO
and heroin
users
[double dagger]

Total number of       15,080       12,007         5146       17,153
non-medical PO,
heroin  users
and both
[double dagger]
                                 Canada

                      M            F          Total

Population of      7,669,070    7,770,165   15,439,235
 Canada

Number of                733          225          958
overdose
deaths *

Lower estimate        36,650       11,250       47,900
(number of
regular illegal
opioid and/or
non-medical
PO users) *

Upper estimate        73,300       22,500       95,800
(number of
regular
illegal
opioid and/or
non-medical
PO users) *

Midpoint              54,975       16,875       71,850
estimate
(number of
regular illegal
opioid and/or
non-medical
PO users) *

Midpoint                 717          217          465
estimate
per 100,000
population *

Total                 55,811       27,905       83,800
number of
regular
illegal
opioid and/or
non-medical PO
users [dagger]

Number of             24,500       10,500       35,000
non-medical
PO-only users
[double dagger]

Number of             14,000         6000       20,000
heroin-only
users
[double dagger]

Number of             11,900         5100       17,000
non-medical PO
and heroin
users
[double dagger]

Total number of       50,400       21,600       72,000
non-medical PO,
heroin  users
and both
[double dagger]

* Based on provincial coroners reports (23)

([dagger]) Based on provincial key informant data (18)

([double dagger]) Sum estimated based on provincial coroners reports
and distribution estimated based on 2005 OPICAN
cohort

PO-prescription opioids

AB-Alberta; BC-British Columbia; ON-Ontario; QC-Quebec

Table 3. Trends of Usage of Non-medical PO-only, Heroin-only,
and Both in the Street Drug Using Population in Edmonton (Alberta),
Vancouver (British Columbia), Toronto (Ontario), Montreal and
Quebec City (Quebec) in the 2002 and 2005 Assessments

                 Edmonton    Montreal    Quebec

POs-only           23.9%       -4.0%       3.5%
Heroin-only          -        -13.9%         -
Combined POs      -17.4%      -16.8%      -10.9%
and heroin

                 Toronto     Vancouver   Overall
POs-only
Heroin-only        -0.8%       0.0%        24.3%
Combined POs       -1.6%      -14.8%       -6.5%
and heroin         -9.6%       -8.2%       -7.5%

Notes:

McNemar test used for significance testing (alpha = 0.05)

Bold numbers show statistical significance

Positive % shows drug abuse increase, whereas negative %
indicates decrease in drug abuse in 2005

- = data were not available for 2005 assessment