Verapamil-Loaded Cubosomes for Enhancing Intranasal Drug Delivery: Development, Characterization, Ex Vivo Permeation, and Brain Biodistribution Studies

Abstract

Verapamil hydrochloride (VRP), an antihypertensive calcium channel blocker drug has limited bioavailability and short half-life when taken orally. The present study was aimed at developing cubosomes containing VRP for enhancing its bioavailability and targeting to brain for cluster headache (CH) treatment as an off-label use. Factorial design was conducted to analyze the impact of different components on entrapment efficiency (EE%), particle size (PS), zeta potential (ZP), and percent drug release. Various in-vitro characterizations were performed followed by pharmacokinetic and brain targeting studies. The results revealed the significant impact of glyceryl monooleate (GMO) on increasing EE%, PS, and ZP of cubosomes with a negative influence on VRP release. The remarkable effect of Poloxamer 407 (P407) on decreasing EE%, PS, and ZP of cubosomes was observed besides its influence on accelerating VRP release%. The DSC thermograms indicated the successful entrapment of the amorphous state of VRP inside the cubosomes. The design suggested an optimized formulation containing GMO (50% w/w) and P407 (5.5% w/w). Such formulation showed a significant increase in drug permeation through nasal mucosa with high E_r value (2.26) when compared to VRP solution. Also, the histopathological study revealed the safety of the utilized components used in the cubosomes preparation. There was a significant enhancement in the VRP bioavailability when loaded in cubosomes owing to its sustained release favored by its direct transport to brain. The I.N optimized formulation had greater BTE% and DTP% at 183.53% and 90.19%, respectively in comparison of 41.80% and 59% for the I.N VRP solution.

Introduction

Verapamil hydrochloride (VRP) is classified as calcium channel blocker prescribed for hypertension, cardiac arrhythmia, angina, etc. [1]. It is also reported as a concomitant therapy for the management of cluster headache (CH) as an off-label use [2, 3]. As reported, it significantly reduced cluster attack frequency and decreased the requirement for ineffective treatments [4]. CH is an extremely severe unilateral headache which strikes many times a day and is associated with ipsilateral autonomic symptoms. Its daily attacks may continue for hours and present as a series (cluster cycle) that may remain for months. This cycle may be followed by a remission period with no apparent symptoms for months or years [5]. Therefore, VRP is prescribed as a first-line prophylactic treatment to decrease the CH severity and reduce the episodes’ frequency during the cluster period [2, 6, 7].

VRP is reported to have poor oral bioavailability (20–35%) related to its hepatic first pass metabolism [8]. Regarding the high solubility and short half-life of VRP, it is a good opportunity to formulate VRP in sustained release preparations for enhancing its bioavailability and extending its pharmacological effect [9].

The intranasal (I.N) route has been elicited as a safe pathway for the effective and rapid management of the CH attacks which are frequently accompanied with severe nausea or vomiting, since the oral administration of drugs may be accompanied by poor gastrointestinal absorption [10]. Consequently, the I.N route, by transporting the drugs along the olfactory sensory neurons, can offer an appealing alternative to oral route [11]. Being non-invasive and painless with no requirements of sterility regulations and physician interventions makes the I.N route promising for drug delivery, especially when targeting the central nervous system. The limitations concerned with the rapid mucociliary clearance can be solved by using mucoadhesive delivery systems for prolonging the contact time with the nasal mucosa [12]. Several nano-colloidal systems proved their efficiency to deliver drugs from the nose directly to the brain, for examples, liposomes [13], niosomes [14], polymeric micelles [15], cubosomes [16], etc. They can physically shield drugs from degradation resulting in boosting their penetration through the nasal mucosa and prolonging their residence at the absorption site [17].

Cubosomes are exceptional nano-colloidal delivery systems whose attractive assembly with a considerable size (10–500 nm) allows them to highly encapsulate many hydrophilic, lipophilic, or amphiphilic drugs [18]. Moreover, biocompatibility, low toxicity, thermodynamic stability, and bioadhesiveness of cubosomes with controlled release properties promote the nasal drug delivery [16]. Glyceryl monooleate (GMO) is an amphiphilic non-toxic and non-irritant polar lipid which can be self-assembled as a honeycomb-like network forming three-dimensional (3D) cubic nano-structures capable for encapsulating the drug candidates [19, 20]. In addition, the presence of non-ionic block copolymers, such as Poloxamer 407 (P407) can enhance the cubosomal stability by preserving the bi-continuous internal structure of cubosomes [21]. Corresponding to the bioadhesion features of cubosomes and their structure resembling the human biomembranes [22], they were selected in our study to examine their capability to encapsulate VRP and the possibility of drug targeting to the brain via the I.N route.

The organized Design of experiments (DoE) system is used to study the relation between various factors and their influence on the experimental outputs [23]. One of its distinctive tools is the factorial design which is more preferred for prediction of responses owing to its flexibility concerning the studied factors and the experimental runs [24]. The optimization technique can be offered leading to producing an innovative product having eligible characteristics [25, 26]. Therefore, three-levels factorial design was followed in this study to differentiate between the factors that can influence the studied responses and the appropriate level of each factor that can exhibit a better optimized output.

Our study aimed at developing nano-structured cubosomes containing VRP using factorial design to study the impact of changing the components’ concentrations on the properties of cubosomes. Various in-vitro characterizations of optimized formulation were conducted. In comparison to the pure VRP solution, the ex-vivo drug permeation through nasal sheep mucosa was studied for the optimized formulation to examine the VRP diffusion through the nasal membrane. Additionally, the optimized formulation was evaluated for its safety, efficacy, and suitability for the I.N administration with assessment of the VRP bioavailability in the rat plasma and its biodistribution into brain.

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Materials

VRP was kindly supplied by Arabian Drug Co., Cairo, Egypt. GMO was gifted by Gattefossé, Saint-Priest, France. P407 was purchased from Sigma Chemical Co., St. Louis, MO, USA. Other solvents and chemicals were of high analytical grade.

Faisal, M.M., Gomaa, E., Ibrahim, A.E. et al. Verapamil-Loaded Cubosomes for Enhancing Intranasal Drug Delivery: Development, Characterization, Ex Vivo Permeation, and Brain Biodistribution Studies. AAPS PharmSciTech 25, 95 (2024). https://doi.org/10.1208/s12249-024-02814-w

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