In recent decades, the development of effective therapies with minimal adverse effects has become a major challenge in the pharmaceutical field. In this context, the industry has invested in innovative drug delivery systems, taking into account factors such as the dosage form, excipients, physicochemical properties of the active pharmaceutical ingredient, and the route of administration. The oral route stands out due to its simplicity, low cost, and high patient acceptance, accounting for more than half of the marketed formulations [1,2].

Despite its popularity, oral administration faces limitations related to the physiological variability of the gastrointestinal tract (GIT), such as gastric emptying time, the absorption window, and the site of drug release. Many drugs are primarily absorbed in the upper small intestine and may be poorly absorbed or degraded throughout the GIT. In this context, modified-release systems—especially gastroretentive drug delivery systems (GRDDS)—have gained prominence [3,4].

GRDDS aim to prolong gastric retention time (GRT), facilitating controlled and localized drug release. These systems are particularly beneficial for drugs with a limited absorption window, instability in alkaline pH, or local action in the stomach. Strategies employed include floating, bioadhesive, expandable and magnetic retention mechanisms [[5], [6], [7]].

Floating systems are widely studied due to their ability to remain suspended in gastric contents and being emptied last, extending GRT and optimizing drug release. They are classified into effervescent systems, which produce CO2 upon contact with gastric acid, and non-effervescent systems, based on hydrophilic polymers that expand with gastric fluids. Both approaches aim to reduce the relative density of the dosage form, maintaining it within the gastric region.

Extending GRT offers important clinical benefits: it improves the bioavailability of drugs with restricted absorption, stabilizes plasma levels, reduces adverse effects, and increases treatment adherence. Drugs such as metronidazole, ranitidine, levodopa, ciprofloxacin, furosemide, and gabapentin are examples of substances that benefit from this technology [8,9].

Among clinical applications, the treatment of *Helicobacter pylori* infections stands out, a bacterium associated with various gastrointestinal diseases, such as ulcers and gastric cancer. GRDDS use has proven effective in ensuring localized and prolonged antibiotic release in the stomach.

The effectiveness of GRDDS is influenced by physiological factors, particularly gastric motility regulated by the migrating motor complex (MMC), which is active during fasting and suppressed postprandially [10]. The MMC comprises four phases of peristaltic activity, with phase III being the most likely for expelling solid dosage forms. Interindividual variability of the MMC presents a challenge for the predictability of GRDDS. Therefore, detailed knowledge of gastric physiology is essential for developing systems effectively adapted to patient profiles [11,12].

Thus, evaluating GIT motor function in the context of drug absorption is essential and may significantly impact drug bioavailability. Therefore, simultaneous monitoring of pharmacokinetic parameters, motility and localization of FFS are important.

Several non-invasive monitoring methods using magnetic resonance imaging and superconducting interference devices have been employed to assess GIT. Among these, the monitoring of magnetic markers (MMM) has gained attention. When MMM is combined with pharmacokinetic data, the method is referred to as pharmacomagnetography (PMG). This approach provides valuable information on the relationship between drug absorption from pellets and their transit through the GIT [13,14].

The alternating current biosusceptometry (ACB) system is an alternative biomagnetic technique for evaluating GRDDS in PMG studies. ACB measures the magnetic susceptibility of magnetic markers and GRDDS using alternating magnetic fields, offering real-time information on their transit through the GIT. The ACB technique provides real-time imaging of biological systems, allows for the monitoring of changes over time, is non-invasive, does not require a magnetically shielded environment, is portable, does not use ionizing radiation and has a lower cost compared to other imaging techniques [[15], [16], [17], [18]].

In summary, gastroretentive drug delivery systems represent a promising strategy to overcome the physiological barriers of the GIT and enhance the therapeutic performance of various drugs, particularly those with low solubility, instability in alkaline pH, or absorption limited to the stomach and the proximal small intestine.

This study aimed to use pharmacomagnetography to evaluate the gastrointestinal transit and pharmacokinetic profile of a floating magnetic prolonged-release tablet administered to healthy volunteers under different prandial states (fasted/fed). A study was performed using metronidazole as a model drug using pharmacomagnetography evaluation based on the ACB technique.