Effect of permeation enhancers and organic acids on the skin permeation of indapamide

Co-amorphous formation of piroxicam-citric acid to generate supersaturation and improve skin permeation

The objective of this study was to prepare a co-amorphous formulation of piroxicam (PIR), a non-steroidal anti-inflammatory drug, and citric acid (CA), and evaluate its skin permeation ability. A spray-drying method was employed to prepare the co-amorphous formulation and its physical properties were characterized. X-ray powder diffraction and thermal analysis confirmed a homogeneous amorphous state, and the infrared spectra revealed intermolecular interactions between PIR and CA, suggesting formation of a co-amorphous formulation of PIR and CA. The PIR-CA co-amorphous formulation exhibited no crystallization for 60 days at 4/25/40°C with silica gel. The PIR-CA co-amorphous formulation increased the solubility of PIR in polyethylene glycol 400 compared with that of the pure drug, and physical mixture (PM) of PIR and CA, confirming a supersaturated state in the formulation. The PIR-CA co-amorphous formulation demonstrated higher skin permeation than PIR alone or PM of PIR and CA, and the flux value was consistent with the degree of saturation. Thus, the increase in the skin permeation of PIR from the PIR-CA co-amorphous formulation directly depended on the increased thermodynamic activity by supersaturation in the absence of interactions between the drug and co-former in the vehicle.

Novel skin penetrating berberine oleate complex capitalizing on hydrophobic ion pairing approach

Berberine hydrochloride (Brb) is a well-known herbal drug that holds a great promise in the recent years thanks to its various pharmacological actions. Currently, Brb is extensively researched as a natural surrogate with evidenced potentiality against numerous types of skin diseases including skin cancer. However, Brb's high aqueous solubility and limited permeability hinder its clinical topical application. In the current work, to enhance Brb's dermal availability, hydrophobic ion pairing approach was implemented combining the privileges of altering the solubility characteristics of Brb and the nanometric size that is usually gained during the ion pairing precipitation process. Sodium oleate (SO) was selected as the complexing agent due to its low toxicity and skin penetrating characteristics. Ion paired berberine oleate complex (Brb-OL) was prepared by simple precipitation technique. Brb-OL complex formation was confirmed by differential scanning calorimetry (DSC), infrared spectroscopy (IR), X-ray powder diffraction (XRD) and saturation solubility studies. It was found that Brb-OL complex formed at stoichiometric binding between oleate and Brb had an average particle size of 195.9 nm and zeta potential of -53.6 mV. The proposed Brb-OL showed 251-fold increase in saturation solubility in n-octanol which confirmed the augmented lipid solubility of the complex compared with free drug. Comparative in-vitro release study showed that Brb-OL complex had much slow and sustained release profile compared to that of free Brb. Furthermore, ex-vivo permeation study using rat skin revealed the enhanced skin permeation of ion-paired Brb-OL complex compared with free Brb. In-vivo study on healthy rats confirmed that topical application of hydrogels enriched with Brb-OL had superior skin penetration and deposition than free Brb as revealed by confocal microscope. Conclusively, ion pair formation between Brb and oleate lead to the formation of more lipophilic Brb-OL complex with nanometric particle size which is expected to be a major progressive step towards the development of a topical berberine formulation.

The advantages of combination therapy on hypertension: development of immediate release perindopril-indapamide tablet and assessment of bioequivalence studies

Hypertension has a major associated risk for organ damage and mortality, which is further heightened in patients with prior cardiovascular events, comorbid diabetes mellitus, microalbuminuria and renal impairment. Convers Plus tablet including perindopril erbumine (PE), which is an angiotensin converting enzyme (ACE) inhibitor, and indapamide, which is diuretic, was designed as a combined tablet to succes in the treatment of hypertension. Physico-pharmaceutical properties and characterization studies were evaluated in vitro conditions. Later on in vivo study was planned as a cross-designed, randomized, open-labeled, single-dose, single-center study via peroral route in 24 healthy male subjects. In this study, bioequivalence with primary pharmacokinetical target parameters reference (Bipreterax 4/1.25 mg Tablet-S.A.Servier Benelux N.V.) and test (Convers Plus 4/1.25 mg Tablet-ARGESAN Pharmaceutical Company) tablets have been found bioequivalent. The results of pharmacokinetic parameters for perindopril, perindoprilat and indapamide were found as Cmax = 23.179 µg/mL, tmax = 0.729 h, t1/2 = 1.429 h; AUC0-t = 26.998 µgs/mL, AUC0-inf = 27.117 µgs/mL; Cmax = 1.834 µg/mL, tmax = 8.792 h, t1/2 = 40.699 h; AUC0-t = 54.828 µgs/mL, AUC0-inf = 77.113 µgs/mL; Cmax = 18.994 µg/mL, tmax = 3.417 h, t1/2 = 16.626 h and AUC0-t = 385.829 µgs/mL, AUC0-inf = 410.728 µgs/mL respectively. In conclusion, physico-pharmaceutical properties and results of clinical trials show that Convers Plus tablets have been found as bioequivalent for perindopril, perindoprilat and indapamide in terms of AUC and Cmax, in 90% confidence limits.

Nanoemulsion-based gel formulation of diclofenac diethylamine: design, optimization, rheological behavior and in vitro diffusion studies

Chronic oral administration of the non-steroidal anti-inflammatory drug, diclofenac diethylamine (DDEA), is often associated with gastrointestinal ulcers and bleeding. As an alternative to oral administration, a nanoemulsion-based gel (NE gel) formulation of DDEA was developed for topical administration. An optimized formulation for the o/w nanoemulsion of oil, surfactant and cosurfactant was selected based on nanoemulsion mean droplet size, clarity, stability, and flowability, and incorporated into the gelling agent Carbopol® 971P. Rheological studies of the DDEA NE gel were conducted and compared to those of conventional DDEA gel and emulgel. The three gels exhibited an elastic behavior, where G' dominated G″ at all frequencies, indicating the formation of strong gels. NE gel exhibited higher G' values than conventional gel and emulgel, which indicated the formation of a stronger gel network. Strat-M® membrane, a synthetic membrane with diffusion characteristics that are well correlated to human skin, was used for the in vitro diffusion studies. The release of DDEA from conventional gel, emulgel and NE gel showed a controlled release pattern over 12 h, which was consistent with the rheological properties of the gels. DDEA release kinetics from the three gels followed super case II transport as fitted by Korsmeyer-Peppas model.

Cocrystals of Hydrochlorothiazide: Solubility and Diffusion/Permeability Enhancements through Drug-Coformer Interactions

Hydrochlorothiazide (HCT) is a diuretic and a BCS class IV drug with low solubility and low permeability, exhibiting poor oral absorption. The present study attempts to improve the physicochemical properties of the drug using a crystal engineering approach with cocrystals. Such multicomponent crystals of HCT with nicotinic acid (NIC), nicotinamide (NCT), 4-aminobenzoic acid (PABA), succinamide (SAM), and resorcinol (RES) were prepared using liquid-assisted grinding, and their solubilities in pH 7.4 buffer were evaluated. Diffusion and membrane permeability were studied using a Franz diffusion cell. Except for the SAM and NIC cocrystals, all other binary systems exhibited improved solubility. All of the cocrystals showed improved diffusion/membrane permeability compared to that of HCT with the exception of the SAM cocrystal. When the solubility was high, as in the case of PABA, NCT, and RES cocrystals, the flux/permeability dropped slightly. This is in agreement with the expected interplay between solubility and permeability. Improved solubility/permeability is attributed to new drug-coformer interactions. Cocrystals of SAM, however, showed poor solubility and flux. This cocrystal contains a primary sulfonamide dimer synthon similar to that of HCT polymorphs, which may be a reason for its unusual behavior. Hirshfeld surface analysis was carried out in all cases to determine whether a correlation exists between cocrystal permeability and drug-coformer interactions.

Transdermal permeation of Kaempferia parviflora methoxyflavones from isopropyl myristate-based vehicles

Kaempferia parviflora (K. parviflora) rhizomes have long been used in traditional folk medicines and as general health-promoting agents. Several biological activities of K. parviflora, especially its anti-inflammatory effect, are due to its major constituents, methoxyflavones. However, the oral bioavailability of these methoxyflavones has been shown to be low. The aim of this study was to investigate the permeation behaviors of K. parviflora methoxyflavones from isopropyl myristate (IPM)-based vehicles. We studied the effects of ethanol and propylene glycol (PG) as the hydrophilic, solvent-type vehicles as well as fatty acids as the permeation enhancers. A permeation experiment was performed in vitro, using side-by-side diffusion cells through the full thickness of pig ear skin. The solubility and permeation of methoxyflavones were able to be modified by choice and ratio of vehicles. The ethanol/IPM vehicle was shown to be more effective in enhancing the solubility and permeation of methoxyflavones when compared to the PG/IPM vehicle. Regarding an optimal balance between solubility or affinity to vehicle and skin to vehicle partition coefficient, the ethanol/IPM vehicle in the ratio of 1:9 maximized the flux. Among the investigated fatty acids, oleic acid showed the greatest enhancing effect on the permeation of methoxyflavones, indicating that saturated fatty acids are less effective than unsaturated fatty acids. Long chain fatty acids increased diffusion coefficient parameter and shortened the lag time. The number of carbon atoms and double bonds of fatty acids did not show direct relation to the profile of permeation of methoxyflavones.

Transdermal delivery of angiotensin II receptor blockers (ARBs), angiotensin-converting enzyme inhibitors (ACEIs) and others for management of hypertension

CONTEXT

Angiotensin II receptor blockers (ARBs), angiotensin-converting enzyme inhibitors (ACEIs) are some of the most commonly prescribed medications for hypertension.

OBJECTIVE

Most of all conventional dosage forms of ARBs and ACEIs undergo extensive first-pass metabolism, which significantly reduces bioavailability. Majority of ARBs and ACEIs are inherently short acting due to a rapid elimination half-life. In addition, oral dosage forms of ARBs and ACEIs have many high incidences of adverse effects due to variable absorption profiles, higher frequency of administration and poor patient compliance.

METHODS

Many attempts have been made globally at the laboratory level to investigate the skin permeation and to develop transdermal therapeutic systems of various ARBs, ACEIs and other anti-hypertensives, to circumvent the drawbacks associated with their conventional dosage form.

RESULTS

This manuscript presents an outline of the transdermal research specifically in the area of ARBs, ACEIs and other anti-hypertensives reported in various pharmaceutical journals.

CONCLUSION

The transdermal delivery has gained a significant importance for systemic treatment as it is able to avoid first-pass metabolism and major fluctuations of plasma levels typical of repeated oral administration. As we can experience from this review article that transdermal delivery of different ARBs and ACEIs improves bioavailability as well as patient compliance by many folds. In fact, the rationale development of some newer ARBs, ACEIs and other anti-hypertensives transdermal systems will provide new ways of treatment, circumventing current limitations for conventional dosage forms.

Effect of chemical enhancers in transdermal permeation of alfuzosin hydrochloride

The objective of the present study is to explore the efficient chemical penetration enhancer among the various enhancers available in overcoming the stratum corneum barrier in transdermal delivery of Alfuzosin hydrochloride (AH). The different enhancers were incorporated in 2% Carbopol gel which was selected as a control and evaluated by in vitro diffusion studies through dialysis membrane and permeation through the rat abdominal skin using Keshary-Chien diffusion cells. All the enhancers increased the release rate through the dialysis membrane when compared with control except oleic acid which decreased the release rate but showed maximum solubility of the drug. Among the various enhancers Transcutol 20% and tween-20 (2%) showed the highest cumulative amount (Q(24)) of 702.28 ± 6.97 μg/cm(2) and 702.74 ± 7.49 μg/cm(2), respectively. A flux rate of 31.08 ± 0.21 μg/cm(2)/hr by Transcutol 20% and 30.38 ± 0.18 μg/cm(2)/hr by tween-20 (2%) was obtained. Transcutol 20% showed decreased lag time of 0.13 ± 0.05 hr. The lowest skin content of 342.33 ± 5.30 μg/gm was seen with oleic acid 2.5%. Maximum enhancement of flux by 3.94-fold was obtained with transcutol 20%. Primary skin irritation studies were performed with rabbit. Histopathological studies of transcutol 20% showed marked changes such as degeneration and infiltration of mononuclear cells in dermis indicating the effect of transcutol on the skin. Among the different enhancers transcutol is efficient in enhancing transdermal delivery of AH.

The control of skin-permeating rate of bisoprolol by ion-pair strategy for long-acting transdermal patches

A moderate drug permeating rate (flux) is desirable for long-acting transdermal patches. In this work, a novel simple method of controlling bisoprolol (BSP) flux by ion-pair strategy was initiated. Different ion-pair complexes including bisoprolol maleate (BSP-M), bisoprolol tartarate, bisoprolol besilate, and bisoprolol fumarate were prepared and their fluxes through rabbit abdominal skin were determined separately in vitro. Furthermore, permeation behavior from isopropyl myristate, solubility index in pressure-sensitive adhesives, determined by DSC, and n-octanol/water partition coefficient (log P) were investigated to illustrate the mechanism of drug permeation rate controlling. The results showed that compared to free BSP (J = 25.98 ± 2.34 μg/cm(2)/h), all BSP ion-pair complexes displayed lower and controllable flux in the range of 0.11 to 4.19 μg/cm(2)/h. After forming ion-pair complexes, the capability of BSP to penetrate through skin was weakened due to the lowered log P and increased molecule weight. Accordingly, this study has demonstrated that the flux of BSP could be controlled by ion-pair strategy, and among all complexes investigated, BSP-M was the most promising candidate for long-acting transdermal patches.

Systemic delivery of antihypertensive drugs via skin

Hypertension is a chronic disease with one of the highest chances of causing death, and long-term treatment is required. The antihypertensive drugs used in the treatment are generally administered orally. The limitations of the oral route make transdermal delivery of drugs more attractive. The transdermal route offers numerous advantages including avoidance of systemic first-pass metabolism and high patient compliance. The transdermal therapeutic systems, popularly known as ‘patches’, deliver drugs across the skin with a constant release rate. However, skin is a unique membrane having excellent barrier properties. Either chemical enhancers or physical methods such as iontophoresis and electroporation have been used to provide effective plasma drug concentrations. This review article focuses on the approaches to enhance skin permeability of antihypertensive drugs for the optimization of transdermal therapeutic systems of these drugs and the research studies intended for the optimization of transdermal dosage forms of antihypertensive drugs are summarized.