There are numerous drugs that are prescribed for medicinal purposes in the treatment of acute and chronic conditions or other medical issues and events. Whilst various prescription drugs may also be misused (e.g., benzodiazepines, opiates/opioids, gabapentinoids, etc.), there are a variety of drugs used recreationally [e.g., heroin, cocaine, cannabis, amphetamine-type stimulants (ATS), etc.]. The use of prescription drugs and drugs of abuse can result in therapeutic or desired effects, respectively, along with negative effects that can include adverse effects such as toxic effects. Often the production of these effects primarily depends on the dose consumed and any acquired tolerance to the effects of the drug. However, there can also be tolerance-independent side effects of a physiological (e.g., rashes, headache, etc.) and psychological nature (e.g., depression, other mood changes, memory, and cognitive impairment, etc.).

Diabetes mellitus is a medical condition that has become increasingly more common and diagnosed within the global population, often related to changes in modern society and obesity. It is essentially a metabolic disorder in which the body is unable to appropriately regulate blood glucose levels, leading to an increase in blood glucose produced from the metabolism of sugar [1]. Glucose levels are regulated by the hormone insulin secreted from β-cells of islets of Langerhans in the pancreas. Complications of untreated diabetes are severe and can cause diabetic ketoacidosis, hyperosmolar hyperglycaemic state, or death [2]. Serious long-term complications include cardiovascular disease (high blood pressure leading to increased risk of coronary heart disease), stroke (as well as cerebrovascular disease including transient ischaemic attack), chronic kidney disease (including nephropathy), neuropathy (with associated pain or numbness), limb issues (peripheral vascular disease leading to limb and foot damage and potentially gangrene) and damage to the eyes (including retinopathy, cataracts and glaucoma) [3].

Diabetes occurs either due to the failure of the pancreas to produce enough insulin or the impairment of body cells’ proper permeability in response to insulin secretion. There are three main types of diabetes mellitus: type 1, type 2, and gestational diabetes [3]. Type 1 diabetes or insulin-dependent diabetes (IDD), as previously defined; also known as juvenile or adolescent diabetes, results from the failure of the pancreas to produce enough insulin as a consequence of loss or damage to beta cells caused by an autoimmune response. The cause of this autoimmune response is unknown (idiopathic). Type 2 diabetes originates from body cell resistance to insulin, whereby cells fail to respond to insulin properly. Taking insulin itself may be required by the patient as the disease progresses. This form was previously referred to as “non-insulin-dependent diabetes mellitus” (NIDDM) or “adult-onset diabetes”. Lastly, gestational diabetes occurs when pregnant women without a previous history of diabetes develop high blood glucose levels.

Due to the intended and unintended effects of drugs, the use of drugs by diabetic individuals can create a variety of associated consequences, both directly (i.e. use of drug causing memory impairment which may result in the patient not taking their insulin or anti-diabetic medication) as well as indirectly as part of the patient’s physiological status (i.e. medical and disease state as a result of diabetes and/or other co-morbidities) [4, 5]. Whilst diabetic patients being prescribed drugs (for diabetes itself or other medical issues) may be monitored closely, this may not be the case for individuals that may be using illicit drugs of abuse. Equally, the impact of using such drugs within a diabetic disease state has not been widely discussed within the medical, pharmaceutical, or toxicological literature. The aim of this article is to highlight the potential issues associated with substance use within the medical context of diabetes, including some initial data pertaining to such drugs used by diabetic patients within a drug rehabilitation setting at the National Rehabilitation Center (NRC) in Abu Dhabi, United Arab Emirates (UAE).

Substance use is common amongst many age groups, including individuals suffering from type 1 and type 2 diabetes. In the UK, a questionnaire study found that 29% of young adults (aged 16–30) with type 1 diabetes responded that they regularly used illicit drugs [6]. In terms of type 2 diabetes which is a developmental condition, some studies have suggested that when used alone or in combination, alcohol, and illicit drugs, might be associated with an earlier onset of type 2 diabetes [7]. Aside from the potential adverse impact on self-care through substance use (e.g., poor nutrition, etc.) that may have an effect of inducing or hindering diabetic control, there can be direct physiological effects of substance use and drugs of abuse in particular. Such drugs are typically associated with certain central nervous system (CNS) and pharmacodynamic effects resulting in categorisation as stimulant, depressant, or hallucinogenic in nature [8].

The NRC provides medical care on an in- and out-patient basis within the context of drug rehabilitation in the UAE [13]. For the purpose of this study, the drug history of 62 patients (55 male, 4 female; aged 22–73 years, median 46 years) who suffer from type 1 (n = 18, insulin-dependent) or type 2 (n = 44) diabetes was noted. The types of substances used and the associated frequency proportion of patients are shown in Table 1.

The most frequent substances involved were amphetamines, alcohol, cannabis, and pregabalin with no particular trend for type 1 or type 2 diabetic patients. As tramadol accounted for 40% of total opiates/opioid cases including combined use of tramadol along with heroin, statistics for tramadol were shown separately. Overall, many patients exhibited poly-drug abuse with CNS depressants predominating, often in combination with amphetamines. Not only does this reflect the drug situation in the region but also reflects the potential challenges and contraindications highlighted elsewhere for these substance types [14]. Of particular note was one patient who was a user of synthetic cannabinoids. These are a class of new psychoactive substances (NPS, formerly referred to as “designer drugs”) that have been used within Europe for nearly 20 years but are relatively new for the region. The issue with these particular substances is that they have a particularly complex pharmacological effect that is beyond that of cannabinoids from the cannabis plant due to their interaction with the endocannabinoid system [type 1 cannabinoid (CB₁) and type 2 cannabinoid (CB₂) receptors] [15]. Synthetic cannabinoids exhibit CNS stimulant (i.e. cardiovascular), depressant (i.e. movement and respiratory), and hallucinogenic (i.e. acute and extreme psychosis) effects. Their direct and indirect impacts on diabetes have not been studied, but given the varying physiological and psychological effects, they arguably pose a significant contraindication and due to the frequency of diabetes in the general population, it is likely that many synthetic cannabinoid users are diabetics. Hence, further study of this sub-population would be of benefit.

Given the increased number of diagnoses of diabetes in the global population as well as the continued prevalence of substance use worldwide, there continues to need to be an understanding of the direct and indirect issues associated with glycaemic control and diabetes as a whole. Many drugs of abuse produce psychological and physiological effects that impede an individual’s ability to self-care, coupled with contraindications for dealing with the disease and its wider impact on patient health status and clinical care.