The obtained data with the two used parameters in this DUS seems to show different results and conclusions, so that both the classification by importance of consumption (expressed as packs/1000/year) and the percentage of each subgroup based on DID varied considerably (Table 2). This is because the two used parameters have different purposes. The use of the “sold units” indicator provides information on the guidelines for the use of a specific therapeutic subgroup within a defined geographical area, in our case, the island of La Gomera and its townships. For example, the tramadol-acetaminophen combination from N02AJ subgroup is the number one option throughout the island and townships, while hydromorphone and oxycodone are the least consumed, barely representing 0.5% of the total. The second option is the N02AX subgroup (tramadol) followed by fentanyl and / or buprenorphine, this order varies in some townships. All they show an increase in the consumption of tramadol in combination with dexketoprofen, displacing the natural opium derivatives. This difference in behavior is due to variations in the number of sold units that do not have to reflect a real variation in consumption.
At the island level, the tramadol-acetaminophen combination represents 63.35% of the total sold units, while in DID it represents 34.73%. Tramadol ranks second in both the number of sold units and its contribution to DID. Natural opium derivatives (subgroup N02AA) represent 4.30% of total consumption (and fourth place in order of consumption), being 5.19% in DID, thus ranking last. Buprenorphine represents only 1.33% of the sold unit´s total, lower than morphine and oxycodone-naloxone, but it ranks third in its contribution to DID with 15.75%. For fentanyl, we have a percentage of 6.29% in the number of sold units, around 10% with respect to tramadol-acetaminophen, in comparison with 14.87% in DID, occupying the fourth position for DID.
Although data expressed in DID provides more accurate information on opioid consumption than simply using the number of sold units, the unexpected findings invite us to analyze the problem from other point of view, for example, by analyzing data on strong or weak opioids separately. Opioids are classified in two groups-the weak (tramadol in monotherapy and combinations) and the strong opioids (the remainders). The data analysis based on this classification shows that the weak opioids are the most consumed, especially, those presentations with lower-dose and lower number of units per package. So, tramadol in combination with acetaminophen for a dose of 37.5/325mg and 20 tablets, covered 74.13% of the total, compared to 13.25% for the presentation of 60 tablets. The remaining correspond to the great dose (75/650mg), although its percentage is decreasing. The most frequent dose and presentation for tramadol was 50 mg and 20 tablets, about 30%, in comparison with 15% of the 100 mg dose and 20 tablets. The oral solution pharmaceutical form also has a relevant and not insignificant role, an average of 13.3%.
In the case of strong opioids, the low-dose and low-unit for package is not always the most consumed form. In the case of fentanyl, the formulations with 400µg dose, 30 tablets, and the patches, especially, 12µg/h and 25µg/h doses and five units are the most frequent. Fentanyl under the form of nasal spray is minority due to its addiction problems (AEMPS, 2020b). A similar situation was observed with buprenorphine, the patches and tablets being the pharmaceutical preparations the most consumed, representing 55% of the total. At present, the consumption of both pharmaceutical forms is very similar.
In the case of natural opium derivatives, we find that the first choice for morphine is tablets with 10mg doses and 12 or 60 units per packages; the oxycodone-naloxone combination predominate the high doses (10mg/5mg and 20mg/10mg) with 28 units per package. Hydromorphone consumed, around 80%, as tablets, 30 units and high-dose (8mg). In all cases, the high-dose was the first option.
The consumption of weak opioids (as DID) in Spain represents 68.28% of the total; tramadol in combination with acetaminophen was the most consumed, indicated in the treatment of moderate to severe intensity pain, whereas tramadol in monotherapy was the second option in severe pain. This tendency in consumption of tramadol is not an isolated event. The use of tramadol has increased worldwide during the last decades. For example, in Denmark, it increased twice its use from 2011 to 2013, (Muller et al. 2019), although a decline in tramadol use was observed from 2014 to 2019 (Sorensen et al. 2021).
In contrast, strong opioids represent 31.72% of the total, being fentanyl with 16.10% of the total, the most outstanding, followed by tapentadol (4.95%), buprenorphine (4.62%), oxycodone combined with naloxone (3.49%) and morphine (1.58%). All of them are prescript for the treatment of pain with very precise indications. Fentanyl is indicated for cancer patients with breakthrough pain or buprenorphine is indicated for the treatment of moderate to severe cancer pain and severe pain that does not respond to non-opioid analgesics (Dowell et al. 2016). A recent study reports a relevant use of fentanyl in noncancer patients (González-Bermejo et al. 2021). The easy administration of transdermal and transmucosal formulations could explain the increase in fentanyl consumption, particularly in Western and Northern European countries and also in Spain (Bosetti et al. 2019; González-Bermejo et al. 2021). Oxycodone-naloxone is indicated for the treatment of severe pain that can only be adequately treated with analgesics opioid, which explains its consumption.
If we compare these data with those obtained in the island of La Gomera we find a different consumption pattern. The weak opioids (as DID) represent 58.67% of the total, tramadol with acetaminophen being the most frequent, with 34.73%, approximately 10 points lower than in Spain whereas the percentage of tramadol in monotherapy is slightly higher in La Gomera (19.96 vs 17.58). The remainder corresponds to tramadol-dexketoprofen, which is three times higher in La Gomera than the nationwide level. However, the percentage of strong opioids represent 41.33%, higher than those observed at the nationwide, 31.72%. In this case, fentanyl and buprenorphine are the most consumed, approximately, an average of 15% of the total each. Between the natural opium derivatives have the morphine (1.83%) and oxycodone-naloxone (2.71%), although their percentages vary slightly, but their net contribution is the same, around 5%. The consumption of oxycodone, hydromorphone and pethidine barely represent 0.36% of the total, while in Spain reached values close to 1%.
This difference in consumption pattern could be related with sociodemographic characteristics and health-related factors among others. Approximately, the half of the population in La Gomera is located in the main city with a high economic level with great access to all essential services, whereas the population in the smallest townships is very disperse, far-away to essential service and oldest people. The proportions of 65 + aged people are 21.4% of the population of La Gomera, the second oldest in the Canary Islands after the island of El Hierro with 22.3% (Istac, 2020). The older people report more pain conditions, especially musculoskeletal pain, and more likely to be prescribed with opioids than younger population (Zin et al. 2014). This creates a dilemma for clinicians, they should prescribe the less potent opioids but with a few adverse effects. However, poorly controlled pain is a public health issue and the personal, familiar and societal cost cannot be measured, especially, at the older age group. All these factors should consider in the therapeutic strategy and if this fails to yield the desired results and/or the quality of patient life is additionally burdened, the overall strategy must be reviewed (O’Brien et al. 2017).
The use of health areas as criteria does not provide any relevant or additional information to those obtained when we refer to the townships for both indicators. This fact has been also observed on the island of El Hierro and the island of Fuerteventura, Canary Island (data not shown).