The World Health Organization (WHO) defines medication adherence to treatment as “the degree to which the person’s behavior corresponds with the agreed recommendations from a healthcare provider” [1]. Adherence means that patients and physicians work together to enhance patient health by taking into account the medical opinion and patient lifestyle, values, and treatment preferences [2].

Medication non-adherence is a complicated and multifaceted healthcare issue. Non-adherent patients may decide to stop taking their medication or not to start treatment at all. Patients may also take higher or lower doses than prescribed or not respect the timing advised [3]. Thus, non-adherence can be caused by the inability of patients to take their recommended treatment due to capacity and resource constraints (problems of accessing prescriptions, medication shortages, cost, and competing demands) [4].

Furthermore, medication availability and affordability are a critical priority issue in low- and middle-income countries, where medication shortage represents a significant public health problem and affordability is considered a serious concern to any healthcare system since it affects patient health and imposes a financial burden on patients, clinicians, and healthcare systems [5]. Strategies that address medication shortage depend on the country’s economic situation and include increased reporting systems, policy changes, medication shortage platforms, and expedited medication approval [6].

Several studies and working groups have examined medication shortage mitigation and management solutions [7,8,9]. A recent survey, based on semi-structured interviews during the COVID-19 period in Michigan hospitals, provided insights to help develop and manage medication shortages [10]. Several studies were also conducted in Arab countries. Two explored the extent of medication shortages in Jordanian hospitals [11] and the opinion of Egyptian physicians on medication shortages [12]. The third evaluated medication shortages in large hospitals in Riyadh using the European Association of Hospital Pharmacists medication shortage questionnaire [13]. However, all these studies did not take into account patient adherence to treatment, despite the shortage issue.

Since the events of October 2019, Lebanon has been experiencing one of the world's worst economic crises, with its currency rapidly devaluating, losing more than 90% of its value. The country's health sector has been negatively impacted by the financial crisis [14], especially given that around half of the population has no health coverage, while the other half is covered by institutions also enduring financial barriers. In 2020, the COVID-19 pandemic and the Beirut port massive explosion aggravated the issue tenfold, putting even more strain on an already struggling healthcare system [14].

While unemployment and financial troubles decrease patient capacity to purchase medications, the shortage of foreign currencies has led the government to gradually lift subsidization on many essential goods, including medications, while other basic goods like food and clothing are becoming more and more expensive, and difficult to acquire [15]. The worse the crisis, the higher the shortage. Indeed, whenever the item is available, it is out of reach of the average individual. In this challenging context, many Lebanese started panic buying and hoarding available medications [14]. The situation has worsened with medications smuggled out of the country and the market flooded with substandard drugs. Consequently, many essential medications have run out, and there could be further shortages of others, while the local industry is having difficulty trying to cope with the new context. Thus, many Lebanese spend time searching the country and beyond for necessary medications [14].

Understanding medication shortages could help create a management plan that includes clear rules and processes for information collection, decision-making, cooperation, and timely communication. However, measuring adherence is critical for researchers and physicians since an inaccurate estimation can lead to several issues that are both costly and harmful. Furthermore, this measure is complex since the parameters of acceptable adherence must be carefully defined and sometimes individually tailored [16]. Several instruments are available for these measures, but they should be valid, reliable, and change-sensitive [17]. In Lebanon, the Lebanese Medication Adherence Scale (LMAS) has been previously developed to measure medication adherence, considering socioeconomic and cultural factors [18]. It was initially validated among hypertensive patients [18] and then in patients with other chronic illnesses in Lebanon [19,20,21], all before the current crisis and medication shortage.

Based on the above, there is a need for a new scale that assesses the effect of medication shortage on adherence. The objective of the current study is to develop and validate a scale to evaluate the harmful impact of medication shortage among the general Lebanese population and assess its correlates and association with medication adherence.