The most abused prescription opioid in our study was
buprenorphine. Its abuse profile was rather similar to that of
methadone, consistent with previous findings [22]. Findings
mostly involved younger age groups, implying drug abuse. The
proportion of abuse for both these drugs was over 80%, with
buprenorphine abuse most common in the age group 20–29, and
methadone abuse peaking among those slightly older, 30–39.
Concentrations of buprenorphine and methadone were low also
among abusers. Buprenorphine and methadone abuse is also
common in other countries. In France, in contrast to Finland,
buprenorphine involves more misuse, intravenous use, and illicit
acquisition than does methadone [23]. Diversion and methadone
leakage from opioid maintenance treatment for abuse purposes are
problems in Norway [24], where both methadone and buprenorphine findings in accidental drug intoxications have increased. In
contrast to Finland, methadone was found in Norwegian bodies
20 times as often as was buprenorphine, despite the fact that
buprenorphine seizures outnumbered those from methadone
[25]. A small portion of all cases of abuse of buprenorphine and
methadone involves prescriptions. Abuse of buprenorphine in
Finland mainly results from smuggled tablets bought on the street.
Although the proportion of methadone abuse in our study was
high, methadone findings were somewhat uncommon. As a pain
medication, methadone use in Finland is rare; in opioid maintenance treatment buprenorphine–naloxone is more frequently used
(in 2011, 0.48 DDD/1000 inhabitants/day [12]) than is methadone
(0.14 DDD/1000 inhabitants/day [12]). Rather than abuser preferences, the dominance of buprenorphine among Finnish drug
abusers may reflect drug availability. In preventing the abuse
problem, regulation of drug availability is vital.
Tramadol was by its figures the second most abused prescription opioid, with an abuse percentage of 29% of all tramadolrelated deaths. This abuse figure was somewhat less than that
reported from the Swedish adverse drug reactions database, where
39% of tramadol-dependent patients were involved in past or
current drug abuse [26]. Our tramadol findings were most
common in those aged 20–39, about 10 years younger than the
31–50 reported in Sweden [26]. The young age profile of deceased
Finnish tramadol abusers and the marked increase in tramadol
seizures by Finnish Customs indicate that tramadol may have a
substantial abuse potential to which health-care professionals
must be alert. Opioids, even weak ones, should be prescribed with
caution and only for valid indications, and evaluation of medication validity during opioid treatment is essential.
Consumption of another weak opioid codeine (in 2011,
10.1 DDD/1000 inhabitants/day [12]) was over three times as high
as that of tramadol (3.0 DDD/1000 inhabitants/day [12]), but in our
data, codeine findings were only 1.5 times as frequent as were
tramadol findings. Codeine was, though, the most frequent opioid
detected in our material. Its abuse involved 16% of the postmortem
codeine cases. A 2009 French survey utilising questionnaires from
pharmacies detected codeine abuse during the past month in 7.5%
of codeine cases [27]. The codeine abuser profile mainly resembled
that of tramadol, consistent with previous findings [22]. Concomitant other opioids and alcohol were common in codeine- and
tramadol-abuser deaths, and drug concentrations were quite high
both among abuser and other cases. Codeine is available only as a
combination product with paracetamol or ibuprofen, or in cough
syrup combinations. No over-the-counter codeine products are
available in Finland, except for some low-concentration cough
syrups. Consuming large doses of codeine combination products
may lead to toxic effects from other substances, a fact which may
somewhat reduce the abuse liability of codeine.
Fentanyl and oxycodone abuser profiles were rather similar.
Abuse of them both was concentrated in young men aged 20–39. No
oxycodone nor fentanyl abuse occurred in those aged above
50. Abusers were somewhat younger than in Australia, where both
oxycodone and fentanyl consumption has been increasing among
the elderly, but there, abusers have mainly been men aged 30–49
[28,29]. Compared with the other opioids studied, fentanyl caused,
in our study, the highest proportions of fatal poisonings and
accidental deaths. This suggests that abuse of this very potent drug
may involve increased risk of fatality. The consumption of
oxycodone (in 2011, 1.4 DDD/1000 inhabitants/day [12]) and
fentanyl (1.2 DDD/1000 inhabitants/day [12]) has notably increased in Finland since the early 2000s [30], but these two were the
least-abused opioids among our cases. In Australia, use of injected
opioids, highly associated with drug abuse and roughly comparable
to our definition of abuse, involved 27% of the oxycodone-related
deaths [28], and as high as 54% of the fentanyl-related deaths
[29]. Oxycodone and fentanyl prescriptions in Australia have
increased, but predominantly as low-dose formulations for older
people, at least in part reflecting appropriate pain treatment
[28,29]. In Finland, as well, decreased morphine consumption in
pain treatment may explain at least some increase in consumption
of other strong opioids [30]. In the United States, however,
increased oxycodone prescription was associated with similar
increases in self-reported non-medical use and increases in
emergency-department visits [31]. Despite the worldwide problem
of opioid abuse, its manifestations vary, and further monitoring at
the national level is important for developing preventive strategies.
Many substance-abuse studies are population-based and
depend on self-reported answers to questionnaires. Substance
abusers usually rarely participate in such studies and underreport
their own abuse. Considering this, one benefit from our study is the
unequivocal identification of specific drugs and their blood
concentrations. As all the postmortem toxicology cases involved
routine screening for opioids by appropriate analytical methods,
opioids were registered regardless of the quality of background
information. Each case underwent individual investigation, first
identifying all 2088 opioid-related cases, and second, assessing the
opioid abuse among these cases by case histories and autopsy and
laboratory findings. Our study has, however, some limitations.
Death certificates were occasionally inadequate in terms of
background information, and some abuser cases were possibly
classified as other use because of inaccurate information. Deaths
associated with suspected drug abuse among young individuals
were regularly subject to medico-legal examination, but medicinal
use of opioids may remain somewhat underestimated due to a
lower autopsy rate among older people. Our abuse proportions
hence reflect the situation among the living, rather than providing
accurate prevalence figures for the Finnish population overall.
Prescription drug abuse is neither safe for an individual nor is it
a minor health problem for society. In connection with the ageing
of the European population, demand for opioid analgesics will
increase, with higher amounts of drugs produced and distributed,
obviously leading to a larger street supply. For Finnish Customs,
the smuggling of medicines and designer drugs is their largest
current problem [32], a problem that is escalating. During 2011,
the quantity of buprenorphine seized was more than sevenfold
that of 2010, and the quantity of other medicines seized doubled
[32]. In future, abuse of medicinal drugs may surpass illicit drug
use and lead to a higher number of drug deaths [33]. Abuser deaths
in our study proved mostly accidental, and the relatively low blood
drug concentrations indicated intravenous abuse. The main
preventive measure against opioid abuse and opioid-related
mortality is prescribing addictive medications cautiously. Furthermore, after the death of someone with opioid medication, the
bereaved should receive proper information on disposal of any
remaining medications. Health care professionals as well as the
public should be enlightened about the increasing problem of
prescription drug abuse.