What do the suffixes - XR, ER, Chrono, Chronosphere - really mean as it pertains to modified-release antiepileptic drugs?

Abstract

Summary Background: Epilepsy is a disease requiring chronic therapy with antiepileptic drugs (AEDs). Many conventional AEDs currently available have either too rapid an absorption or elimination, requiring the patient to take multiple doses per day, which may adversely impact adherence or cause peak‐related side‐effects. Consequently, some AEDs with immediate‐release characteristics have been modified to prolong absorption and/or reduce peak serum concentration, enabling dosage regimen simplification. Modified‐release (MR) AED formulations have been labelled with various suffixes or names (‘XR, ER, ‐Chrono, ‐Chronosphere’), but such labelling may not adequately distinguish those MR AEDs with the most prolonged absorption or unique formulation characteristics. Such suffixes lack precise definition. Objective: We identified the formulation characteristics of currently available MR AEDs, attempting to distinguish them by suffix designation. Design/methods: Nine MR AED formulations, representing six different AEDs, were characterized, utilizing information from FDA‐approved inserts (2001 +) and published literature. Results: The formulation characteristics of commercially available MR AEDs are quite variable and do not appear to correlate with their brand name suffix. Conclusions: When all MR AEDs are compared, suffix designations do not provide distinguishable information about formulation characteristics. Clarification of MR AED suffix terminology may be warranted.

Assessing bioequivalence of generic modified-release antiepileptic drugs

“…13,14 Manufacturers of generic MR products are permitted to use different delivery technologies than reference products, and these often varied between generic and reference AED formulations. Forty-two generic MR-AED products were evaluated in 97 BE studies, enrolling 3,175 healthy participants.…”

Extended‐release antiepileptic drugs: A comparison of pharmacokinetic parameters relative to original immediate‐release formulations

“…Various innovative drug delivery technologies (e.g., Microtrol technology, OROS, DiffCore, hydrophilic matrix) have been developed to minimize the fluctuations in plasma drug levels seen with IR products (Table 1) (Reed et al., 2010). Medications used to treat a range of disorders have been prepared using these technologies, and the resulting improvements in PK profiles have increased patient adherence through simplified dosing schedules (Saini et al., 2009) and have enabled dose increases in an effort to achieve greater efficacy (Miller et al., 2004; Smith et al., 2004).…”

Generic medicines literacy — minimising the potential for patient confusion

“…Different formulations may also use a suffix to indicate distinguishing properties, such as “dispersible” in Rulide D (Sanofi‐Aventis) or “osmotic release oral system” in Adalat OROS (Bayer Schering). However, these suffixes, while meaningful, can be a source of misunderstanding about dosing intervals and length of action, leading to errors 2 . A standard nomenclature does not exist, even for formulation descriptors.…”

“…The Food and Drug Administration in the United States and the Therapeutic Goods Administration in Australia have developed documents outlining approved medicines terminology, 2 , 3 but there are no official lists of approved suffixes or prefixes. The Institute for Safe Medication Practices, a non‐profit US‐certified patient safety organisation internationally regarded as an expert in medication safety, has recognised this problem and maintains a list of products with drug name suffixes and their meanings 4…”