Microneedle-assisted delivery of verapamil hydrochloride and amlodipine besylate

Contents lists available at European Journal of Pharmaceutics and Biopharmaceutics Microneedle-assisted delivery of verapamil hydrochlorideand amlodipine besylate Monika Kaur Kevin B. Ita ,, Inna E. Popova , Sanjai J. Parikh , Daniel A. Bair a College of Pharmacy, Touro University, Mare Island-Vallejo, CA, USAb Department of Land, Air and Water Resources, University of California, Davis, CA, USA The aim of this project was to study the effect of stainless steel solid microneedles and microneedle roll- Received 28 August 2013 ers on percutaneous penetration of verapamil hydrochloride and amlodipine besylate.
Accepted in revised form 14 October 2013 Available online 28 October 2013 yl-pentanenitrile is a calcium channel blocker agent that regulates high blood pressure by decreasingmyocardial contractilty, heart rate and impulse conduction. Amlodipine, (R, S)-2-[(2-aminoethoxy) Transdermal drug delivery calcium channel blocker that is used for the management of hypertension and ischemic heart disease.
Passive penetration of verapamil and amlodipine across the skin is low. In vitro studies were performed with microneedle-treated porcine ear skin using vertical static Franz diffusion cells (PermeGear, Heller- town, PA, USA). The receiver chamber contained 5 ml of PBS (pH7.4) and was constantly maintained at Transcutaneous flux 37 °C temperature with a water circulation jacket. The diffusion area of the skin was 1.77 cm2. The donorcompartment was loaded with 1 ml of the solution containing 2.5 mg/ml of amlodipine besylate. Thedonor chamber was covered with parafilm to avoid evaporation. Passive diffusion across untreated por-cine skin served as control. Aliquots were taken every 2 h for 12 h and analyzed by liquid chromatogra-phy–mass spectrometry. Transcutaneous flux of verapamil increased significantly from 8.75 lg/cm2/h to49.96 lg/cm2/h across microneedle-roller treated porcine skin. Percutaneous flux of amlodipine besylatefollowing the use of stainless steel microneedles was 22.39 lg/cm2/h. Passive flux for the drug was1.57 lg/cm2/h. This enhancement of amlodipine flux was statistically significant. Transdermal flux ofamlodipine with microneedle roller was 1.05 lg/cm2/h in comparison with passive diffusion flux of0.19 lg/cm2/h. The difference in flux values was also statistically significant. Stainless steel solid micro-needles and microneedle rollers increased percutaneous penetration of verapamil hydrochloride andamlodipine besylate. It may be feasible to develop transdermal microneedle patches for these drugs.
Ó 2013 Elsevier B.V. All rights reserved.
hypertension is usually caused by another condition such as kidneydisease or tumors .
to the American Heart Association about 76.4 million Several approaches have been used to manage hypertension.
people over age of 20 and older have high blood pressure in the Angiotensin converting enzyme (ACE) inhibitors are used to lower United States . According to the World Health organization, sub- the vasoconstrictor angiotensin II. Angiotensin receptor blockers optimal BP (>115 mmHg SBP) is responsible for 62% of cerebrovas- act on AT1 and AT2 receptors to interrupt the action of angiotensin cular disease and 49% of ischemic heart disease Environmental II . Calcium channel blockers (CCBs) are antihypertensive agents factors or genetics usually predispose individuals to hypertension.
used to mediate the transport of calcium in cardiac and vascular High sodium intake, lack of exercise, stress levels or obesity can cells. CCBs help relax blood vessels to reduce the workload of the result in high blood pressure. Essential hypertension can go undiagnosed as it does not have identifiable cause. Secondary In this study, two antihypertensive drugs, verapamil and amlo- dipine, were investigated for transdermal drug delivery. Verapamil,2-(3, 4-dimethooxyphenyl)-5-[2-(3,4 dimethoxyphenyl) ethyl-methyl-amino]-2-propan-2-yl-pentanenitrile, is a calcium channel ⇑ Corresponding author. College of Pharmacy, Touro University, 1310 Club Drive, Mare Island-Vallejo, CA 94592, USA. Tel.: +1 7076385994; fax: +1 7076385266.
blocking agent. It is used in treatment of hypertension, angina pec- E-mail address: (K.B. Ita).
toris and supraventricular arrhythmias . Increased calcium 1 Present address: Department of Plant, Soil and Entomological Sciences, University channel blockers concentration in the plasma would result of Idaho, Moscow, ID, USA.
0939-6411/$ - see front matter Ó 2013 Elsevier B.V. All rights reserved.
M. Kaur et al. / European Journal of Pharmaceutics and Biopharmaceutics 86 (2014) 284–291 improved cardiovascular condition. Transdermal delivery of verap- and then drug loaded patch is applied for the penetration of the amil will increase the concentration of the systemic verapamil that drug across the skin. This mechanism is known as ‘poke and patch'.
would increase therapeutic efficacy. Amlodipine, (R, S)-2-[(2- Solid microneedles create microchannels that can remain open for period of 72 h under occlusive conditions . In vivo studies have methoxycarbonyl-6-methyl-1, 4-dihydropyridine, is also a calcium been conducted that showed that solid stainless steel microneedle channel blocker that is used to treat hypertension and ischemic application followed by insulin patch lowered blood glucose levels Amlodipine partition coefficient in two different phases was re- rollers (dermarollers) are stainless steel micronee- ported in the literature. The two phases were n-octanol/water and dle-embedded cylindrical surface that rolls over the skin to create n-octanol/phosphate buffer saline. Log K values obtained were 2.96 micropores. Badran et al. studied the effect on microneedle length and 3.09, respectively Verapamil partition coefficient (log P) and chemical penetration enhancers on the transdermal penetra- value obtained using octanol and water was 3.8 The permeabil- tion of hydrophilic drug molecules across full thickness human ity of these drugs across the skin is low. Several strategies have skin. The hydrophilic substances investigated in the experiment been used to overcome the excellent barrier properties of the stra- were carboxyfluorescein and radiolabeled mannitrol. Micropores tum corneum to enhance transdermal drug delivery. One approach created by dermarollers were visualized using light microscopy is the application of microneedles to increase percutaneous and scanning electron microscopy (SEM). Skin treated with derma- roller had higher transepidermal water loss values in comparison Transdermal microneedles create micron sized pores in the skin with intact skin .
to enhance delivery of the drug across the skin. Micron sized nee- aim of the present study was to investigate microneedle- dles are ideal for patient adherence as they do not stimulate nerves mediated transdermal delivery of antihypertensive agents – verap- that are associated with pain. Microneedles improve patient com- amil hydrochloride and amlodipine besylate across pig skin.
pliance as patient with needle phobia will be more likely to apply Stainless steel microneedles and microneedle rollers were used the patch because of its painlessness. Additionally, patients can in our investigation to determine transcutaneous fluxes of administer the drug by themselves . Microneedle-mediated verapamil and amlodipine across pig skin. This paper focuses on drug delivery only disrupts the stratum corneum and epidermis microneedle-assisted transdermal delivery of verapamil hydro- but it does not reach nerve fibers and blood vessels in the dermis chloride and amlodipine besylate through porcine ear skin.
Patients with gastrointestinal tract irritation are more likelyto benefit from the use of microneedle mediated patches as the 2. Materials and methods drug gets directly into systemic circulation. Furthermore, drugswith poor absorption rate and instability are ideal for transdermal 2.1. Chemicals and reagents drug delivery Transdermal drug delivery is beneficial to pa-tients with chronic conditions such as diabetes. Furthermore, it is buffered saline (PBS), verapamil hydrochloride and useful for patients that have poor adherence as they are taking amlodipine besylate were purchased from Sigma Aldrich Co. (St.
multiple medications or going through illness where they simply Louis, MO, USA). Porcine ears were obtained from Animal Technol- forget to take the medication at the right time such as those suffer- ogies (Tyler, TX, USA). Double distilled ionized water was prepared ing from Alzheimer's disease. Microneedle-mediated transdermal using NanoPure Infinity Ultrapure water purification system.
drug delivery reduces skin irritation Factors that affect the diffusion rate across the skin are micro- 2.2. Stainless steel microneedles needle density, microneedle length, number of applications anddrug concentrations. According to Gomaa et al., increase in the stainless steel microneedle arrays (manufactured microneedle density led to increase in the level of drug penetration by NanoBioSciences LLC, Sunnyvale, CA) were supplied by Stanford across the skin The studies also demonstrated that applica- University Biomaterials and Advanced Drug Delivery Laboratory.
tion of longer microneedles increased the drug diffusion through These were used to create microchannels in porcine skin for trans- skin. Multiple applications of the microneedles and higher concen- dermal drug delivery. Microneedle rollers were purchased from tration of the drug solution in the donor chamber of the Franz ver- New Skin Care Collection, Tallahassee, Florida, USA.
tical cells led to an increase in transdermal drug delivery.
Hollow microneedles are designed with channels that deliver medications and extract biological fluids . Controlled drug diffu- 2.3. Skin preparation sion is achievable with hollow microneedles where drug deliveryrate can range from fast to slow diffusion and it can be used for Animal Care and Use Committee (IACUC), Touro time-dependent delivery across the skin. Hollow microneedles University, Mare Island-Vallejo, CA approved the experiments.
can be fabricated from glass, polymer and metal. Insulin delivery Pig ears were obtained from Animal Technologies (Tyler, Texas, through hollow microneedles was shown to reduce the blood glu- USA). Skin pieces were thawed at room temperature and cleaned cose levels in type 1 diabetic patients . During hollow micronee- with tap water. An electric clipper was used to trim pig ear hairs.
dle application, upper layer of the skin is disrupted and the drug is An electric dermatome (Robbin's Instruments, Chatham, NJ, USA) released into the skin. This is known as ‘poke and flow' . These was used to section the skin to a thickness of 550 lm. Porcine ears microneedles are used to deliver liquid drugs across the skin as it is were then stored at a temperature of 20 °C for no longer than two facilitated by pressure-driven flow months before use.
Solid microneedles are applied to skin with pressure that cre- ates micron sized holes in the skin for penetration of the drug 2.4. Diffusion studies across the skin Silicon, polymers, metal and ceramic are exam-ples solid microneedles. Metals such as stainless steel have been vitro permeation experiments were conducted using vertical used to create needles (i.e. hypodermic needles) for decades .
Franz diffusion cells. Microneedle-treated porcine skin, derma- Furthermore, stainless steel microneedles provide good mechani- tomed to 550 lm was mounted on the donor chambers of three cal strength and are easy to cut with laser beam . Microchan- cells having an area of 1.77 cm2. Three cells with untreated pig skin nels are created after insertion and removal of the microneedles, served as controls. The volume of the diffusion cells was 12 ml. The

M. Kaur et al. / European Journal of Pharmaceutics and Biopharmaceutics 86 (2014) 284–291 upper donor chamber and lower receiver chamber of the Franz ver- verapamil hydrochloride and amlodipine besylate. The micronee- tical cell were fastened together by means of a clamp, along with dles had a density 187 needles/cm2 and each microneedle was skin between the two chambers. 2 ml of verapamil solution 500 lm long.
(50 mg/ml) or amlodipine besylate (2.5 mg/ml) was loaded onto DermaRoller is a device that contains microneedles mounted on donor chambers and covered with Parafilm. Aliquots of the recep- cylindrical surface that rolls over the skin. There were 540 micro- tor solution were collected at the interval of 2 h for a 12 h period.
needles mounted on cylindrical drum that were 500 lm in length.
The samples were stored at 4 °C until analysis by liquid chroma- The images () were collected using HTC one-X camera.
tography–mass spectrometry (LC–MS). Receptor chambers were Scanning electron microscopy was used to visualize the stain- replenished by an equal volume of fresh phosphate buffer solution.
less steel microneedles and microconduits. The top view shows All of the six receptor chambers contained a magnetic stirrer to that microneedles were aligned symmetrically. The image from maintain constant concentration.
the side view shows that needles are sharp-tipped. SEM image ofsingle microneedle determines the length and width of the micro- 2.5. LC–MS analysis Microconduits created across pig skin by microneedles deter- S/MS analysis was performed using an Agilent mine the disruption of the stratum corneum, which acts as an series 1200 HPLC with diode-array and Agilent 6320 Ion Trap mass excellent barrier to transdermal penetration. It also shows that spectrometer detector (Agilent Technologies, Palo Alto, CA). Chro- microneedles successfully penetrated the skin to create microp- matographic separation was carried out on the reverse-phase Agi- ores. demonstrates that microchannels are symmetrical lent Zorbax Eclipse Plus C18 (100  2.1 mm, 3.5 lm) analytical across porcine skin. Single microconduit has diameter of 100 lm column, which was protected by a guard column with the same that allows diffusion of small hydrophilic molecules ).
stationary phase (12.5  4.6 mm, 5 lm) (Agilent Technologies, PaloAlto, CA). Column temperature was set at 40 °C, and autosamplertemperature was set at 4 °C. The mobile phase consisted of 0.1% In vitro permeation studies formic acid in water (solvent A), and 0.1% formic acid in methanol(solvent B). The gradient was performed at 0.4 ml/min with an ini- In vitro permeation experiments were conducted to study the tial condition of 10% of mobile phase B for 2 min. Mobile phase B transdermal delivery of two antihypertensive agents – verapamil was increased to 90% at 3 min and held at 90% B to 8 min. Calibra- hydrochloride and amlodipine besylate. The experiments were tion curve standards were freshly prepared in PBS buffer solution.
performed on porcine skin using stainless steel microneedles.
The MS data were collected in the positive ESI MS/MS mode. Neb- Porcine skin was used to investigate transdermal drug delivery be- ulizer temperature was 350 °C, nebulizer pressure was 50 psi, and cause it is a good model of human skin. Pig ear skin was mounted the drying gas flow rate was 10.0 l/min. Compounds were quanti- between donor and receiver compartment, where the drug was fied in positive ESI MS/MS mode by quantifying specific parent ion.
loaded into the donor chamber and aliquots were collected from UV spectra were collected for each compound.
receiver chamber. Liquid chromatography–mass spectrometry(LC–MS) was used to determine the concentration of the drug in 2.6. Characterization of the microneedles and microconduits – SEM the samples. Cumulative amount versus time graphs for passivediffusion and microneedle-mediated diffusion were plotted electron microscopy (SEM) was performed at the Elec- tron Microscopy Laboratory, Department of Medical Pathology andLaboratory Medicine, School of Medicine, University of California atDavis. SEM was used to visualize stainless steel microneedles and Transdermal drug flux the microchannels created in porcine skin. The device wasmounted onto an aluminum stub using DUCO cement mix with Flux values were determined using steady-state portion of the carbon shavings (for conductivity), sputter coated with gold using cumulative amount versus time curves . Percutaneous pen- a PELCO SC-7 coater and viewed on the FEI XL 30 scanning electron etration of the drug across non-treated pig skin (controlled skin) microscope. Skin was fixed with Karnovsky's fixative in 0.1 M so- was low. Passive transdermal drug flux for verapamil hydrochlo- dium phosphate buffer then washed with 0.1 M sodium phosphate.
ride and amlodipine besylate were 8.75 lg/cm2/h and 1.57 lg/ Dehydration was accomplished in increasing concentrations of cm2/h respectively. In our study, transdermal flux of verapamil ethanol through 100% ethanol and critical point dried in a Tousimis after DermaRoller application was 49.96 lg/cm2/h () while 931.GL Autosamdri critical point dryer. The mites were mounted transcutaneous flux of amlodipine besylate following solid micro- on aluminum stubs and sputter coated with gold using a PELCO needle application was 22.39 lg/cm2/h (Drug flux value SC-7 coater. The samples were viewed on an FEI XL30 TMP SEM.
for amlodipine besylate following passive diffusion was 0.19 lg/cm2/h when compared to flux value obtained (1.05 lg/cm2/h) fol- 2.7. Statistical analysis lowing twelve passes of stainless steel microneedle roller ( software was used for statistical analysis. Mann– Whitney rank sum test was used to determine the statistical signif-icance of data obtained from the experiments. Mean of replicatemeasurements (n = 3) with corresponding standard errors (SE)was used to plot the graphs.
3.1. Characterization of microneedles and microconduits Fig. 1a. Stainless steel microneedles, density 187 microneedles/cm2 and 500 lm in steel microneedles were applied onto porcine skin to length. (For interpretation of the references to color in this figure legend, the reader study percutaneous penetration of antihypertensive drugs – is referred to the web version of this article.)

M. Kaur et al. / European Journal of Pharmaceutics and Biopharmaceutics 86 (2014) 284–291 Fig. 1b. DermaRoller, total-540 microneedles. (For interpretation of the referencesto color in this figure legend, the reader is referred to the web version of thisarticle.) Fig. 2b. Displays side view of microneedles.
Fig. 1c. Closer view of cylindrical drum of DermaRoller. (For interpretation of thereferences to color in this figure legend, the reader is referred to the web version ofthis article.) Fig. 2c. Visualized single microneedles.
Fig. 2a. Shows top view of stainless steel microneedles using SEM.
Fig. 3a. Shows microchannels created by using scanning electron microscopy.
Our results indicate that enhanced permeation of verapamil hydrochloride was statistically significant after the application of dose of the drug is administered at once. With transdermal patches, microneedle roller. For amlodipine besylate, there was also statisti- there is gradual release of the active ingredient.
cally significant enhancement in transdermal fluxes when solid and medications are administered transdermally, the drug microneedle rollers were used. Stainless steel solid microneedles passes through the stratum corneum, epidermis and dermis. The and microneedle rollers were successfully used to breach the epider- stratum corneum which is the thin (15–20 lm) and outermost mis creating microchannels that allowed percutaneous penetration layer of the epidermis poses a major obstacle for transdermal across pig ear skin. Transcutaneous drug delivery is beneficial for pa- absorption. This layer is made up of corneocytes filled with keratin tients who face limitations posed by oral or parental drug adminis- embedded in a lipid matrix. The lipid matrix consists of ceramides, tration such as first-pass metabolism, gastric irritation and erratic cholesterol and free fatty acids. Dermis is the innermost layer that absorption . Furthermore, transdermal drug delivery is more contains nerves, blood vessels, lymph vessels, hair follicles, seba- advantageous in comparison with bolus delivery method, where full ceous glands and sweat glands Meyer et al. showed that M. Kaur et al. / European Journal of Pharmaceutics and Biopharmaceutics 86 (2014) 284–291 Fig. 6. Shows passive and microneedle-assited transdermal permeation of amlo- Fig. 3b. Visualize the presence of single microscope using scanning electron dipine besylate after microneedle roller application across pig ear skin (500 lm length, 540 density). (For interpretation of the references to color in this figurelegend, the reader is referred to the web version of this article.) Fig. 7a. Displays drug flux of verapamil through passive (non-treated skin,controlled) diffusion and microneedle roller treated pig skin (p-value < 0.05). (For Fig. 4. Shows passive diffusion and microneedle-mediated diffusion of verapamil interpretation of the references to color in this figure legend, the reader is referred with microneedle roller across pig skin. (For interpretation of the references to color to the web version of this article.) in this figure legend, the reader is referred to the web version of this article.) Fig. 7b. Displays transdermal flux of amlodipine desylate through passive (non-treated skin, controlled) and microneedle-treated skin after application of solid Fig. 5. Displays transdermal penetration of amlodipine across non-treated skin and microneedles (stainless steel solid microneedles, 500 lm length, and density of microneedle-treated skin after solid microneedle was applied (stainless steel solid 187 microneedle/cm2) (p-value < 0.05). (For interpretation of the references to color microneedle, 500 lm length, and density of 187 microneedle/cm2). (For interpre- in this figure legend, the reader is referred to the web version of this article.) tation of the references to color in this figure legend, the reader is referred to theweb version of this article.) porcine ear skin has structural characteristics similar to human ducted. Elmahjoubi et al. demonstrated a successful disruption of skin. Light microscopy, transmission electron microscopy and cryo the stratum corneum by measuring transepidermal water loss scanning electron microscopy methods were used to observe stra- using Aquaflux probe. Transepidermal water loss (TEWL) measures tum superficiale dermidis of pig ear skin. The results reported by the water vapor flux crossing the skin into external environment the authors show that pig skin can be used as a model for human integument. In addition, they also reported the storage conditions Different strategies have been used to increase transdermal per- for pig skin at temperature 4 °C . Our pig skin samples were meation of the molecules such as iontophoresis, sonophoresis and kept at the same temperature before permeation studies were con- chemical penetration enhancers. Iontophoresis uses mild electric M. Kaur et al. / European Journal of Pharmaceutics and Biopharmaceutics 86 (2014) 284–291 variables were increased-number of microneedle arrays, micronee-dle length and drug concentration in the donor chamber .
our experiment, stainless steel dermarollers and micronee- dles were utilized to study the transcutaneous penetration ofverapamil hydrochloride and amlodipine besylate. Digital imagesof stainless steel microneedles and dermarollers are shown inOur results demonstrated increased transdermal drugdelivery of verapamil hydrochloride and amlodipine besylate inin vitro percutaneous experiments. In addition, scanning electronmicroscopy was used to visualize microneedles. Li et al. usedSEM technique to characterize maltose microneedles and metaldermarollers. The authors also investigated transcutaneous perme-ation of human Immunoglobulin G across hairless rat skin Park et al. demonstrated improvement in the transdermal absorp- Fig. 7c. Shows transdermal flux of amlodipine besylate across porcine skin using tion of acetylsalicylic acid across human and porcine cadaver skin microneedle rollers (p-value < 0.05). (For interpretation of the references to color in using microneedle roller. Microneedle rollers create multiple inser- this figure legend, the reader is referred to the web version of this article.) tions as the roller rotates across the skin . Zhou et al. showedenhancement in the penetration of insulin on microneedle-roller current to deliver charged molecules across the skin. Ita and Banga treated rat skin. The results obtained showed that longer length showed increased transcutaneous absorption of penbutolol sulfate microneedle rollers led to increased reduction of blood glucose le- across porcine using iontophoresis. Anodal iontophoresis was used vel in comparison with shorter microneedle. The characterization to demonstrate enhancement in transdermal delivery of penbuto- of the microchannels was performed using Evan's blue staining lol sulfate because the molecule is positively charged Yamam- oto et al. studied in vitro and in vivo permeation of naloxone by our investigation, microconduits were visualized using scan- anodal iontophoresis. Anodal iontophoresis involves transfer of ning electron microscope. The presence of micropores was showed positively charged molecule across the epidermal barrier by using that microneedles penetrated the stratum corneum. Kumar et al.
electrorepulsion. The investigators reported enhancement of conducted experiments to test transdermal delivery of calcein in vitro transdermal diffusion of naloxone across pig and rat skin and human growth hormone across porcine skin using maltose using iontophoresis, which was proportional to current intensity.
microneedles. The presence of microchannels was shown by meth- In addition, in vivo Iontophoretic patches were able to delivery nal- ylene blue staining. In addition, they also determined the unifor- oxone across dorsal skin of a rat . Even though iontophoresis mity among the micropores through calcein imaging Banga allows increase in transdermal penetration of small and hydro- et al. showed that microchannels created in the skin after the philic molecules, it can only deliver molecules smaller than application of the microneedles are large enough to allow the pen- 13 kDa . Wang et al. also discussed about skin irritation caused etration of wide range of molecules as they are in nanometer by iontophoresis at higher electric voltage .
dimensions. Disruption of the stratum corneum after microneedle Another most commonly used technique used to investigate application was confirmed by histological sectioning of skin sam-ples .
transdermal permeation studies is the use of chemical penetration hydrochloride and amlodipine besylate have low enhancers . Chemical enhancers are substances that are used penetration rates across the skin. Xie et al. conducted experiments to increase the permeability of the skin. Puglia et al. demonstrated that showed transdermal delivery of calcein and bovine serum effects of polyunsaturated fatty acids (PUFA) and chemical enhanc-ers on permeation of atenolol across human skin The results of albumin, which have small molecular structure and hydrophilic the experiment showed increase in atenolol permeation flux with nature, respectively. Franz diffusion cells were used to study calce- PUFA and transcutol penetration enhancers. Two polyunsaturated in and BSA diffusion across rat skin using coated microneedles fatty acids tested in their experiments were eicosapentaenoic acid Park et al. also showed transdermal delivery of calcein, bovine ser- (EPA) and docosahexaenoic acid (DHA), which increased transder- um albumin and macromolecular proteins using biodegradable mal absorption of atenolol. Lee et al. also investigated the transcu- microneedles (also known as polymeric microneedles) across hu- taneous absorption of lidocaine across pig skin and human skin man cadaver skin. Successful percutaneous penetration of calcein after chemical penetration enhancers were applied. Application of and human growth hormone across pig skin have been reported N-methyl pyrrolidone (NMP) and isopropyl myristate (IPM) where calcein represents a small molecular weight molecule and showed significant increase in transdermal absorption of lidocaine, hGH acts as a larger molecule of 22 kDa .
which improved permeation profile by increasing drug solubility channel blockers are antihypertensive agents used to and partitioning into the skin. Although chemical penetration manage high blood pressure. To maintain normal blood pressure, enhancers improve percutaneous absorption of the molecules, L-type voltage gated calcium channels play an important role as many of them cause skin irritations at higher concentrations .
they regulate constriction of the vascular smooth muscle and car- Our experiment involved the use of microneedles to investigate diac muscle. Verapamil and amlodipine are L-type calcium channel the transport of antihypertensive agents across porcine skin. Sev- blockers that belong to distinct chemical classes, phenylalkylam- eral variables effect the percutaneous penetration of the molecule ines and dyhydropyridines, respectively Verapamil has low across the skin such as microneedle length, microneedle density, bioavailability where only 10–20% of the verapamil dose get and insertion force and insertion time. In addition, microneedle fab- absorbed from the digestive tract into circulatory system in rication material and design also impacts transcutaneous delivery unchanged form On the other hand, amlodipine has a of the molecules. In most studies, it has been proven that increased bioavailability of 65%, longer half-life and it takes longer for the microneedle length and microneedle density enhance permeation concentration to reach maximum because of high tissue affinity of the molecules across epidermis. Li et al. studied transdermal Even though amlodipine has benefits if taken orally, it still delivery of antibodies using maltose microneedles. It was proven poses limitations to patients due to gastric irritation, erratic that human IgG delivery was increased when the following absorption and an initial high plasma concentration.
M. Kaur et al. / European Journal of Pharmaceutics and Biopharmaceutics 86 (2014) 284–291 hypertensive patients have poor adherence to existing Adamson and Pat Kysar of the Electron Microscopy Laboratory, medications. Most of the tablets are taken in the oral form that Department of Medical Pathology and Laboratory Medicine, School passes through liver to get metabolized, known as first pass metab- of Medicine, University of California at Davis for technical assis- olism effect. In addition, oral medications have higher risk of ad- tance and Touro University, California for financial support.
verse effects due to variable absorption profile. Patients onchronic conditions are required to take medication on daily basisto manage their condition. Most of them are on therapy that re- quires taking medication twice or three times a day. Sometimes,patients miss doses of their medications due to amnesia. This can be resolved with transdermal patches. Furthermore, patients' com- pliance decreases with parental route of drug administration be- cause of needle phobia or needle pain usually caused by conventional hypodermic needles. Li et al. reported that pain in- duced by microneedles of length 500–1500 lm is relatively low compared to hypodermic needles .
of transdermal delivery include stable plasma con- centrations. Administration of the drugs through transdermal patches is free of pain, avoids the risk of transmission of blood borne pathogen and allows patient compliance due to ease of use, especially for elder patients. Microneedle-mediated transder- mal drug delivery reduces the chance of infections and skin irrita- tions Gomaa et al. studied transcutaneous penetration of low molecular weight heparin nadroparin calcium using dissolvable microneedles. Since LMWH are large molecules, hydrophilic and have low bioavailability, they are administered parentally. Parental route of drug administration is associated with pain, and safety is- sues. According to National patient safety agency, 2716 incidents were reported related to safety concerns. Transdermal drug deliv- ery has proven to be better alternative for administration of LMWH as successful percutaneous delivery was reported by the authors results of our study show that the increase in transdermal flux of verapamil hydrochloride across porcine skin following the application of microneedle roller was statistically significant (p < 0.05). Amlodipine besylate flux also increased significantly after application of solid microneedles and microneedle rollers (p < 0.05). Further in vitro studies will be conducted to test other variables that effect transdermal dug flux such as microneedle de- sign, length, density, and drug concentrations. In addition, different techniques such as iontophoresis, sonophoresis and chemical enhancers can be combined with microporation to study the effect on percutaneous penetration of these antihypertensive agents. Fu- ture studies would also involve in vivo studies to investigate the efficiency of transdermal drug delivery systems for verapamil hydrochloride and amlodipine besylate.
iated transdermal drug delivery is beneficial for patients with chronic conditions such as hypertension, diabetes and Alzheimer's disease. Transdermal patches are convenient for patients as it allows for self-administration and it is a pain-free process that produces no biohazardous waste. Due to these advan- tages, it has the capability to improve patient's adherence to phar- macotherapy. The results of this study show that application of stainless steel microneedles increased transdermal delivery of verapamil hydrochloride and amlodipine besylate across porcine ear skin. These results show that transdermal patches can be devel- oped for these antihypertensive drugs.
The authors are grateful to Dr. Jayakumar Rajadas of Stanford University Biomaterials and Advanced Delivery Laboratory for the supply of Adminpatch stainless steel microneedle arrays; Grete M. Kaur et al. / European Journal of Pharmaceutics and Biopharmaceutics 86 (2014) 284–291

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