Pharmacokinetic characterisation of transdermal delivery systems

Recent Advances in the Polish Research on Polysaccharide-Based Nanoparticles in the Context of Various Administration Routes

Polysaccharides are the most abundant polymers in nature. They exhibit robust biocompatibility, reliable non-toxicity, and biodegradable character; thus, they are employed in multiple biomedical applications. The presence of chemically accessible functional groups on the backbone of biopolymers (amine, carboxyl, hydroxyl, etc.) makes them suitable materials for chemical modification or drug immobilisation. Among different drug delivery systems (DDSs), nanoparticles have been of great interest in scientific research in the last decades. In the following review, we want to address the issue of rational design of nanoparticle (NP)-based drug delivery systems in reference to the specificity of the medication administration route and resulting requirements. In the following sections, readers can find a comprehensive analysis of the articles published by authors with Polish affiliations in the last few years (2016-2023). The article emphasises NP administration routes and synthetic approaches, followed by in vitro and in vivo attempts toward pharmacokinetic (PK) studies. The 'Future Prospects' section was constructed to address the critical observations and gaps found in the screened studies, as well as to indicate good practices for polysaccharide-based nanoparticle preclinical evaluation.

Recent Advancement of Medical Patch for Transdermal Drug Delivery

Transdermal patches are a non-invasive method of drug administration. It is an adhesive patch designed to deliver a specific dose of medication through the skin and into the bloodstream throughout the body. Transdermal drug delivery has several advantages over other routes of administration, for instance, it is less invasive, patient-friendly, and has the ability to bypass first-pass metabolism and the destructive acidic environment of the stomach that occurs upon the oral ingestion of drugs. For decades, transdermal patches have attracted attention and were used to deliver drugs such as nicotine, fentanyl, nitroglycerin, and clonidine to treat various diseases or conditions. Recently, this method is also being explored as a means of delivering biologics in various applications. Here, we review the existing literatures on the design and usage of medical patches in transdermal drug delivery, with a focus on the recent advances in innovation and technology that led to the emergence of smart, dissolvable/biodegradable, and high-loading/release, as well as 3D-printed patches.

Beneath the Skin: A Review of Current Trends and Future Prospects of Transdermal Drug Delivery Systems

The ideal drug delivery system has a bioavailability comparable to parenteral dosage forms but is as convenient and easy to use for the patient as oral solid dosage forms. In recent years, there has been increased interest in transdermal drug delivery (TDD) as a non-invasive delivery approach that is generally regarded as being easy to administer to more vulnerable age groups, such as paediatric and geriatric patients, while avoiding certain bioavailability concerns that arise from oral drug delivery due to poor absorbability and metabolism concerns. However, despite its many merits, TDD remains restricted to a select few drugs. The physiology of the skin poses a barrier against the feasible delivery of many drugs, limiting its applicability to only those drugs that possess physicochemical properties allowing them to be successfully delivered transdermally. Several techniques have been developed to enhance the transdermal permeability of drugs. Both chemical (e.g., thermal and mechanical) and passive (vesicle, nanoparticle, nanoemulsion, solid dispersion, and nanocrystal) techniques have been investigated to enhance the permeability of drug substances across the skin. Furthermore, hybrid approaches combining chemical penetration enhancement technologies with physical technologies are being intensively researched to improve the skin permeation of drug substances. This review aims to summarize recent trends in TDD approaches and discuss the merits and drawbacks of the various chemical, physical, and hybrid approaches currently being investigated for improving drug permeability across the skin.

Predicting transdermal fentanyl delivery using physics-based simulations for tailored therapy based on the age

Transdermal fentanyl patches are an effective alternative to the sustained release of oral morphine for chronic pain management. Due to the narrow therapeutic range of fentanyl, the concentration of fentanyl in the blood needs to be carefully monitored. Only then can effective pain relief be achieved while avoiding adverse effects such as respiratory depression. This study developed a physics-based digital twin of a patient by implementing drug uptake, pharmacokinetics, and pharmacodynamics models. The twin was employed to predict the in-silico effect of conventional fentanyl transdermal in a 20–80-year-old virtual patient. The results show that, with increasing age, the maximum transdermal fentanyl flux and maximum concentration of fentanyl in the blood decreased by 11.4% and 7.0%, respectively. However, the results also show that as the patient's age increases, the pain relief increases by 45.2%. Furthermore, the digital twin was used to propose a tailored therapy based on the patient's age. This predesigned therapy customized the duration of applying the commercialized fentanyl patches. According to this therapy, a 20-year-old patient needs to change the patch 2.1 times more frequently than conventional therapy, which leads to 30% more pain relief and 315% more time without pain. In addition, the digital twin was updated by the patient's pain intensity feedback. Such therapy increased the patient's breathing rate while providing effective pain relief, so a safer treatment. We quantified the added value of a patient's physics-based digital twin and sketched the future roadmap for implementing such twin-assisted treatment into the clinics.

RETRACTED: Transdermal delivery of flurbiprofen from polyoxypropylene-polyoxyethylene block copolymer stabilized reduced graphene oxide to manage pain in spondylitis: In vitro and in vivo studies

This article has been retracted: please see Elsevier Policy on Article Withdrawal (http://www.elsevier.com/locate/withdrawalpolicy). This article has been retracted at the request of the Editor-in-Chief. Significant similarities were noticed post-publication between this article and the article that was previously published by an apparently unrelated group of authors: Weifan Li, Guangqi Zhang and Xiaoxia Wei, Journal of Biomaterials Applications 35 (2021) 1034 https://doi.org/10.1177/0885328220988462. Moreover, the authors did not respond to the journal request to comment on these similarities and to provide the raw data, and the Editor-in-Chief decided to retract the article. One of the conditions of submission of a paper for publication is that authors declare explicitly that the paper has not been previously published and is not under consideration for publication elsewhere. As such this article represents an abuse of the scientific publishing system. The scientific community takes a very strong view on this matter and apologies are offered to readers of the journal that this was not detected during the submission process.

Transdermal buprenorphine for pain management in children

Pain is one of the main symptoms reported by sick children, particularly by those suffering from cancer. Opioids are very useful in controlling this symptom but they are burdened with significant side effects that limit their use in children. Buprenorphine is a strong opioid that, due to its particular pharmacological characteristics, ensures excellent pain relief with fewer side effects than other opioids. The transdermal formulation allows for good pain control associated with optimal compliance by patients and few limitations on daily life. Unfortunately, transdermal buprenorphine use remains off-label for the control of chronic pain in children; therefore, it is desirable that new studies can validate its use in the paediatric population. This review aims to analyse the clinical advantages of transdermal buprenorphine in the paediatric population and the possible side effects registered in daily clinical practice.

Development of gliclazide ionic liquid and the transdermal patches: An effective and noninvasive sustained release formulation to achieve hypoglycemic effects

Ionic liquids (IL) technology provides a useful platform to achieve the topical delivery of therapeutic agents, because of its capability to improve skin permeability. While the majority of the researches aimed to achieve local action by topical IL delivery, systemic action of therapeutic agents by local topical application has rarely been reported. In the present work, Gliclazide (GLI), a second-generation sulfonylurea drug was transformed into an IL with tributyl(tetradecyl)phosphonium for the first time. The physicochemical properties of this IL were systematically characterized by DSC, TGA, FT-IR, NMR, and HPLC. The transdermal patch based on this IL was further prepared using DURO-TAK®87-4098. The fabricated gliclazide based ionic liquid [P_6,6,6,14][GLI] transdermal patch displayed satisfactory in vitro and in vivo performance. The [P_6,6,6,14][GLI] patch released 88.17% of the loaded drug within a 3-day period in the in vitro dissolution test, confirming its sustained release property. Meanwhile, GLI effectively permeated through the artificial skin from [P_6,6,6,14][GLI] transdermal patch in the in vitro skin permeation test, with the permeation rate and lag time of 16.571 ± 0.328 μg/cm²/h and 3.027 ± 0.154 h respectively. The [P_6,6,6,14][GLI] transdermal patch showed favorable PK profile in rat as compared with GLI oral suspension. The relative bioavailability of GLI reached 92.06% of GLI oral suspension, while the C_max was significantly reduced. Most importantly, [P_6,6,6,14][GLI] transdermal patch demonstrated superior hypoglycemic effect to the oral suspension both in the fasted and fed condition, confirming the feasibility of systemic action by local topical delivery of IL. In addition, the [P_6,6,6,14][GLI] transdermal patch caused no skin irritation based on histopathological analysis.

Clinical pharmacology and dosing regimen optimization of neonatal opioid withdrawal syndrome treatments

In this paper, we review the management of neonatal opioid withdrawal syndrome (NOWS) and clinical pharmacology of primary treatment agents in NOWS, including morphine, methadone, buprenorphine, clonidine, and phenobarbital. Pharmacologic treatment strategies in NOWS have been mostly empirical, and heterogeneity in dosing regimens adds to the difficulty of extrapolating study results to broader patient populations. As population pharmacokinetics (PKs) of pharmacologic agents in NOWS become more well‐defined and knowledge of patient‐specific factors affecting treatment outcomes continue to accumulate, PK/pharmacodynamic modeling and simulation will be powerful tools to aid the design of optimal dosing regimens at the patient level. Although there is an increasing number of clinical trials on the comparative efficacy of treatment agents in NOWS, here, we also draw attention to the importance of optimizing the dosing regimen, which can be arguably equally important at identifying the optimal treatment agent.

Thermoresponsive gating membranes embedded with liquid crystal(s) for pulsatile transdermal drug delivery: An overview and perspectives

Due to the circadian rhythm regulation of almost every biological process in the human body, physiological and biochemical conditions vary considerably over the course of a 24-h period. Thus, optimal drug delivery and therapy should be effectively controlled to achieve the desired therapeutic plasma concentrations and therapeutic drug responses at the required time according to chronopharmacological concepts, rather than continuous maintenance of constant drug concentrations for an extended time period. For many drugs, it is not always necessary to constantly deliver a drug into the human body under disease conditions due to rhythmic variations. Pulsatile drug delivery systems (PDDSs) have been receiving more attention in pharmaceutical development by providing a predetermined lag period, followed by a fast or rate-controlled drug release after application. PDDSs are characterized by a programmed drug release, which may release a drug at repeatable pulses to match the biological and clinical needs of a given disease therapy. This review article focuses on thermoresponsive gating membranes embedded with liquid crystals (LCs) for transdermal drug delivery using PDDS technology. In addition, the principal rationale and the advanced approaches for the use of PDDSs, the marketed products of chronotherapeutic DDSs with pulsatile function designed by various PDDS technologies, pulsatile drug delivery designed with thermoresponsive polymers, challenges and opportunities of transdermal drug delivery, and novel approaches of LC systems for drug delivery are reviewed and discussed. A brief overview of all academic research articles concerning single LC- or binary LC-embedded thermoresponsive membranes with a switchable on-off permeation function through topical application by an external temperature control, which may modulate the dosing interval and administration time according to the therapeutic needs of the human body, is also compiled and presented. In the near future, since thermal-based approaches have become a well-accepted method to enhance transdermal delivery of different water-soluble drugs and macromolecules, a combination of the thermal-assisted approach with thermoresponsive LCs membranes will have the potential to improve PDDS applications but still poses a great challenge.

Transdermal patches: Design and current approaches to painless drug delivery

Use of transdermal patches can evade many issues associated with oral drug delivery, such as first-pass hepatic metabolism, enzymatic digestion attack, drug hydrolysis and degradation in acidic media, drug fluctuations, and gastrointestinal irritation. This article reviews various transdermal patches available in the market, types, structural components, polymer role, and the required assessment tools. Although transdermal patches have medical applications for smoking cessation, pain relief, osteoporosis, contraception, motion sickness, angina pectoris, and cardiac disorders, advances in formulation development are ongoing to make transdermal patches capable of delivering more challenging drugs. Transdermal patches can be tailored and developed according to the physicochemical properties of active and inactive components, and applicability for long-term use. Therefore, a number of chemical approaches and physical techniques for transdermal patch development are under investigation.

The Effect of Low-Dose Nitroglycerin Ointment on Skin Flap Necrosis in Breast Reconstruction after Skin-Sparing or Nipple-Sparing Mastectomy

Background

Skin flap necrosis is a common complication after mastectomy and breast reconstruction. It has been proven that nitroglycerin ointment, as a topical vasodilator, can decrease the rate of skin flap necrosis after mastectomy and breast reconstruction. However, nitroglycerin can cause several side effects, including headache, dizziness, and hypotension. The purpose of this study was to evaluate whether the application of a low dose of nitroglycerin ointment reduced the rate of skin flap necrosis in breast reconstruction after skin-sparing or nipple-sparing mastectomy.

Methods

A total of 73 cases of breast reconstruction after nipple-sparing and skin-sparing mastectomy at our institution from March 2012 to January 2017 were retrospectively studied. Of these patients, 52 received nitroglycerin ointment (4.5 mg) application to the skin around the nipple-areolar complex from August 2015 to January 2017, while 21 received fusidic acid ointment from March 2012 to August 2015. The number of patients who experienced necrosis of the breast skin flap was counted in both groups.

Results

Skin flap necrosis developed in 2 (3.8%) patients who were treated with nitroglycerin ointment and 5 (23.8%) patients who did not receive nitroglycerin ointment treatment. Patients who did not receive nitroglycerin ointment treatment had a significantly higher risk of mastectomy skin flap necrosis than patients who did (odds ratio=7.81; 95% confidence interval, 1.38 to 44.23; P=0.02).

Conclusions

Low-dose nitroglycerin ointment administration significantly decreased the rate of skin flap necrosis in patients who underwent breast reconstruction after skin-sparing or nipple-sparing mastectomy, without increasing the incidence of the side effects of nitroglycerin.

Pharmacokinetics of Memantine after a Single and Multiple Dose of Oral and Patch Administration in Rats

Memantine is a non-competitive N-methyl-D-aspartate (NMDA) receptor antagonist used to treat Alzheimer's disease. We investigated memantine pharmacokinetics after oral, IV and patch administration in rats, and compared memantine pharmacokinetics after multiple- or single-dose oral and transdermal administration. Venous blood was collected at preset intervals in single- and multiple-dose studies. Non-compartmental pharmacokinetics was analysed for all formulations. The oral, IV and patch memantine doses were 10 mg/kg, 2 mg/kg and 8.21 ± 0.89 mg/kg, respectively. The maximum plasma concentration was lower and the half-life longer after patch administration than oral and IV administration. Memantine bioavailability was 41 and 63% for oral and patch administration, respectively. Steady state was achieved around 24 hr for oral and patch administration. The mean AUC increased after oral or patch administration from single to multiple dose. The memantine patch formulation displayed a longer duration of action and lower peak plasma concentration. However, drug exposure was similar to the oral formulation at each dose. Additionally, the memantine patch formulation displayed a smaller interindividual variability and lower accumulation than the oral formulation.

Alternate Routes of Administration of Antidepressant and Antipsychotic Medications

Objective: To review the administration of antidepressant and antipsychotic medications via inhaled, intranasal, buccal, sublingual, transdermal, and rectal routes. Data Sources: A PubMed search was conducted for all data through March 31, 2015 to identify pertinent literature. Search terms included the generic name of each antidepressant and antipsychotic medication in combination with the following terms: alternate routes of administration, inhaled, intranasal, buccal, sublingual, transdermal, and rectal. Study Selection and Data Extraction: English-language case reports, studies, and reviews describing medication administration in human subjects were included. Data Synthesis: Commercially available products that use an alternative route of administration include loxapine for inhalation, asenapine for sublingual administration, and selegiline for transdermal administration. Case reports and studies describe intranasal, sublingual, and transdermal routes of administration of antipsychotic medications as well as buccal, sublingual, transdermal, and rectal administration of antidepressant medications. The concordance between the physicochemical properties possessed by some antipsychotic and antidepressant agents and the physicochemical properties required for nontraditional routes of administration suggest that administration via alternative routes may be feasible for some of these drugs. Further exploration of drug absorption via alternative routes in addition to consideration of patient and formulation factors may yield improvements in medication therapy for patients with psychiatric illnesses. Conclusions: For patients unable to tolerate oral or injectable therapy, administration of psychotropic medications via nontraditional routes may be feasible. The development of alternative routes of drug delivery could prevent discontinuation of needed medication therapy.

Programmable transdermal clonidine delivery through voltage-gated carbon nanotube membranes

Oral dosage forms and traditional transdermal patches are inadequate for complex clonidine therapy dosing schemes, because of the variable dose/flux requirement for the treatment of opioid withdrawal symptoms. The purpose of this study was to evaluate the in vitro transdermal flux changes of clonidine in response to alterations in carbon nanotube (CNT) delivery rates by applying various electrical bias. Additional skin diffusion studies were carried out to demonstrate the therapeutic feasibility of the system. This study demonstrated that application of a small electrical bias (-600 mV) to the CNT membrane on the skin resulted in a 4.7-fold increase in clonidine flux as compared with no bias (0 mV) application. The high and low clonidine flux values were very close to the desired variable flux of clonidine for the treatment of opioid withdrawal symptoms. Therapeutic feasibility studies demonstrated that CNT membrane served as the rate-limiting step to clonidine diffusion and lag and transition times were suitable for the clonidine therapy. Skin elimination studies revealed that clonidine depletion from the skin would not negatively affect clonidine therapy. Overall, this study showed that clonidine administration difficulties associated with the treatment of opiate withdrawal symptoms can be reduced with the programmable CNT membrane transdermal system.

The development of the rotigotine transdermal patch: a historical perspective

The rotigotine transdermal system is a dopamine receptor agonist delivered over a 24-hour period. It is approved for the treatment of idiopathic Parkinson's disease (PD). This article reviews the development of the rotigotine transdermal system, including rotigotine's receptor profile, steady-state pharmacokinetics, and metabolism. Preclinical studies of rotigotine in animal models of PD and proof-of-concept studies in patients with PD are reviewed. These preclinical and clinical studies established this system as an effective method for providing continuous rotigotine delivery across the skin providing the basis for continued clinical development of rotigotine for the treatment of early and advanced PD.

Pharmacokinetics, Tolerability, and Performance of a Novel Matrix Transdermal Delivery System of Fentanyl Relative to the Commercially Available Reservoir Formulation in Healthy Subjects

A novel transdermal formulation of fentanyl-containing dipropylene glycol droplets dispersed in a silicone matrix with a rate-controlling membrane was developed. Healthy male subjects (n = 24) received repeated 72-hour applications of fentanyl (50 mug/h) as the novel matrix and the conventional reservoir formulations in a randomized, 2-way crossover study. Blood samples were collected, and serum concentrations of fentanyl were assayed using liquid chromatography with mass spectrometry detection. The mean area under the curve (AUCtau) and peak concentrations (C(max)) of the matrix formulation were 84 838 pg.h/mL and 1680 pg/mL, respectively. Ratio and 90% confidence intervals of AUCtau and C(max) between the 2 formulations were within 80% to 125%. Adherence of the matrix formulation was higher than the reservoir formulation (62.5 vs 56.2%, P < .0001), without affecting skin irritation. Vital signs and adverse events of the 2 formulations were similar in nature and frequency. The novel matrix formulation displayed enhanced adherence and resulted in similar pharmacokinetics and tolerability as the reservoir formulation.

Pharmacokinetics and Pharmacodynamics of a Transdermal Contraceptive Patch and an Oral Contraceptive

This open-label, randomized, 2-way crossover study characterized the pharmacokinetics and pharmacodynamics of a transdermal contraceptive patch and a norgestimate-containing oral contraceptive. Healthy women (n = 34) applied a patch once weekly for 3 consecutive weeks during each of 2 cycles and received an oral contraceptive for 21 consecutive days during each of 2 cycles. Plasma concentrations of norelgestromin and ethinyl estradiol peaked and waned after daily oral contraceptive administration, whereas they rose and reached steady-state levels after first patch application. Norelgestromin exposure was similar; ethinyl estradiol exposure was higher for the patch than oral contraceptive. Hepatic estrogenic activity, assessed by hepatic globulin synthesis, was similar for corticosteroid-binding globulin and corticosteroid-binding globulin-binding capacity and higher for sex hormone-binding globulin for the patch versus oral contraceptive. The clinical significance of the differences in pharmacokinetic and pharmacodynamic profiles between the patch and oral contraceptive is not fully known. No serious adverse events or discontinuations due to adverse events were recorded.

In-vitro and in-vivo transdermal iontophoretic delivery of tramadol, a centrally acting analgesic

Objectives

The feasibility of transdermal delivery of tramadol, a centrally acting analgesic, by anodal iontophoresis using Ag/AgCl electrodes was investigated in vitro and in vivo.

Methods

To examine the effect of species variation and current strength on skin permeability of tramadol, in-vitro skin permeation studies were performed using porcine ear skin, guinea-pig abdominal skin and hairless mouse abdominal skin as the membrane. In an in-vivo pharmacokinetic study, an iontophoretic patch system was applied to the abdominal skin of conscious guinea pigs with a constant current supply (250 µA/cm2) for 6 h. An intravenous injection group to determine the pharmacokinetic parameters for estimation of the transdermal absorption rate in guinea pigs was also included.

Key findings

The in-vitro steady-state skin permeation flux of tramadol current-dependently increased without significant differences among the three different skin types. In the in-vivo pharmacokinetic study, plasma concentrations of tramadol steadily increased and reached steady state (336 ng/ml) 3 h after initiation of current supply, and the in-vivo steady-state transdermal absorption rate was 499 µg/cm2 per h as calculated by a constrained numeric deconvolution method.

Conclusions

The present study reveals that anodal iontophoresis provides current-controlled transdermal delivery of tramadol without significant interspecies differences, and enables the delivery of therapeutic amounts of tramadol.

Formulation and evaluation of press coated tablets for pulsatile drug delivery using hydrophilic and hydrophobic polymers

The aim of present investigation was to develop press coated tablet for pulsatile drug delivery of ketoprofen using hydrophilic and hydrophobic polymers. The drug delivery system was designed to deliver the drug at such a time when it could be most needful to patient of rheumatoid arthritis. The press coated tablets containing ketoprofen in the inner core was formulated with an outer shell by different weight ratio of hydrophobic polymer (micronized ethyl cellulose powder) and hydrophilic polymers (glycinemax husk or sodium alginate). The release profile of press coated tablet exhibited a lag time followed by burst release, in which outer shell ruptured into two halves. Authors also investigated factors influencing on lag time such as particle size and viscosity of ethyl cellulose, outer coating weight and paddle rpm. The surface morphology of the tablet was examined by a scanning electron microscopy. Differential scanning calorimeter and Fourier transformed infrared spectroscopy study showed compatibility between ketoprofen and coating material.

Origin of pain in migraine: evidence for peripheral sensitisation

Migraine is the most common neurological disorder, and much has been learned about its mechanisms in recent years. However, the origin of painful impulses in the trigeminal nerve is still uncertain. Despite the attention paid recently to the role of central sensitisation in migraine pathophysiology, in our view, neuronal hyperexcitability depends on activation of peripheral nociceptors. Although the onset of a migraine attack might take place in deep-brain structures, some evidence indicates that the headache phase depends on nociceptive input from perivascular sensory nerve terminals. The input from arteries is probably more important than the input from veins. Several studies provide evidence for input from extracranial, dural, and pial arteries but, likewise, there is also evidence against all three of these locations. On balance, afferents are most probably excited in all three territories or the importance of individual territories varies from patient to patient. We suggest that migraine can be explained to patients as a disorder of the brain, and that the headache originates in the sensory fibres that convey pain signals from intracranial and extracranial blood vessels.

Nitroglycerin headache and nitroglycerin-induced primary headaches from 1846 and onwards: a historical overview and an update

Nitroglycerin (NTG) (glyceryl trinitrate) was synthesized by the Italian chemist Ascanio Sobrero in Paris in 1846. A very unstable explosive, Alfred Nobel while working on explosives, combined it with Kiselguhr and patented it as dynamite in 1867. NTG was introduced in 1879 in medicine in the treatment of angina pectoris by the English doctor William Murrell. NTG-induced headache was quickly recognized as an important adverse event both in the industrial use of NTG, where it was used to produce dynamite, as well as in the use of NTG as drug. This review traces the evolution of our understanding of NTG headache.

Rotigotine transdermal delivery for the treatment of Parkinson's disease

BACKGROUND

Rotigotine is a non-ergot dopamine agonist that has been developed as a new transdermal formulation, and is indicated for use in early (USA and Europe) and advanced (Europe only) Parkinson's disease (PD). The potential advantages of the rotigotine patch include immediacy of effect onset as intestinal absorption in unneeded, constant drug delivery, and ease of use via application of a once-daily adhesive patch. An interesting element of this profile is constant drug delivery, which may avoid pulsatile dopaminergic stimulation, which has been postulated to be related to the development of motor complications.

OBJECTIVE

To consider the evidence surrounding the profile of rotigotine and, in particular, whether its constant delivery system offers significant benefits to the treatment of early and advanced PD.

METHODS

Source material was identified using a PubMed search for the term 'rotigotine' (up to March 2008). The review focuses only on publications related to the rotigotine indication for PD.

RESULTS/CONCLUSION

The rotigotine transdermal patch demonstrates clinical efficacy, alongside a tolerability profile that appears to be well within the range of that observed with other non-ergot dopamine agonists. The once-daily patch formulation may favour compliance but, in similarity with the other theoretical advantages of constant drug delivery (for example reduced emergence of motor complications, improved tolerance to peripheral AEs), requires further detailed study.

[Transdermal therapeutic systems for drug administration]

Transdermal therapeutic systems, or transdermal patches, facilitate controlled release of active ingredients through the skin and into the systemic circulation. Drugs administered through such systems escape first pass metabolism and steady state is maintained similar to a continuous intravenous infusion for up to several days. Few pharmacologically active substances can currently be administered through transdermal patches and production is technically demanding. Research is ongoing to improve the systems and expand the indications. This article gives a brief overview over principles behind various transdermal patch types, as well as the advantages and disadvantages of transdermal therapeutic systems.

Transdermal drug pharmacokinetics in man: Interindividual variability and partial prediction

A database of human dermatopharmacokinetic parameters of 12 transdermal patches is established. The effect of system design, application site, and metabolism on pharmacokinetic data is discussed, and interindividual variability of data and its possible sources evaluated. Using multiple regression analysis, two equations based on drugs physicochemical characteristics are suggested for partial prediction of peak plasma concentration (C(max)) after patch application. Patch application presumably decreases variance as rub-off, wash and exfoliation steps are diminished. The results showed that interindividual variation, in terms of coefficient of variation (CV) of C(max), is inversely correlated with drugs molecular weight and lipophilicity in the range of 200<MW<400 and 1.6<logK(oct)<4.3. Multiple regression analysis of C(max) against physichochemical parameters demonstrated the prominent contribution of hydrogen bonding acceptability of the molecules on their maximal plasma concentration after patch administration. The findings suggest that the serum concentration profile for transdermal therapeutic systems (TTS) is a net result of the system performance, drug absorption and elimination. Thus, the variability in serum concentration is a function of variability of each process involved. This should be noted in explanation of effect of molecular features of drugs on their plasma concentration profile.

Rotigotine transdermal system for the treatment of Parkinson's disease

BACKGROUND

Levodopa has been the cornerstone of the treatment of Parkinson's disease (PD) for >30 years, but long-term levodopa therapy is associated with development of such motor complications as motor fluctuations, dyskinesias, and drug-induced involuntary movements. Rotigotine is a dopamine agonist with high affinity for the D(2) receptor. Rotigotine transdermal system, the first such system approved by the US Food and Drug Administration for the management of PD, has been formulated to deliver a consistent concentration of drug to the bloodstream with the goal of minimizing the complications associated with pulsatile dosing.

OBJECTIVE

This article reviews the clinical pharmacology, pharmacokinetic and pharmacodynamic properties, tolerability, and efficacy of rotigotine transdermal system in the treatment of PD.

METHODS

MEDLINE (1966-April 2008) and International Pharmaceutical Abstracts (1971-April 2008) were searched using the term rotigotine. All prospective, randomized clinical efficacy trials in humans were included. The reference lists of the identified articles were reviewed for additional publications.

RESULTS

In clinical trials, rotigotine transdermal system at doses ranging from 4.5 to 67 mg/d was associated with significant clinical benefit in patients with early and advanced PD. In 4 randomized, doubleblind, placebo-controlled trials of 6 months' duration, patients receiving rotigotine transdermal system had significant improvements on the Unified Parkinson's Disease Rating Scale (UPDRS) part II (activities of daily living) that ranged from -0.3 to -4.2, compared with +0.92 to -2 for placebo (P < 0.001, rotigotine transdermal system vs placebo). In one trial that included pramipexole as an active comparator, the change in UPDRS II at 6 months was -4.2 in the rotigotine transdermal system group and -4.6 in the pramipexole group (P = NS, rotigotine transdermal system vs pramipexole). Changes on the UPDRS III (motor examination) at 6 months ranged from -3.58 to -8.7 with rotigotine transdermal system, compared with +0.38 to -4.3 in the placebo group and -10.3 in the pramipexole group (P < 0.001 vs placebo; P = NS vs pramipexole). The change in "off" time at 6 months ranged from -2.1 to -2.7 hours with rotigotine transdermal system, compared with -0.9 hour with placebo and -2.8 hours with pramipexole (P < 0.001 vs placebo; P = NS vs pramipexole). The proportion of patients achieving a >30% reduction in "off" time ranged from 55.1% to 59.7% of patients receiving rotigotine transdermal system, compared with 34.5% to 35.0% of patients receiving placebo and 67.0% of patients receiving pramipexole (P<0.001 vs placebo; P = NS vs pramipexole). The most commonly reported adverse event was application-site reaction, occurring in 9% to 46% of patients receiving rotigotine transdermal system, compared with 5% to 13% of patients receiving placebo. Other adverse events occurring in >20% of patients receiving rotigotine transdermal system were somnolence(8%\2-33%)and nausea(12%-49%). Less than 5% of patients assigned to rotigotine transdermal system discontinued study medication because of an adverse drug event.

CONCLUSIONS

The available evidence suggests that rotigotine transdermal system was effective compared with placebo in decreasing morbidity in patients with early and advanced PD. The most commonly reported adverse events associated with rotigotine transdermal system were application-site reaction, nausea, and somnolence. Additional clinical trials are needed to determine the long-term tolerability profile of rotigotine transdermal system and its clinical efficacy and tolerability compared with oral dopamine agonists.

A randomized, open, parallel group, multicenter trial to investigate analgesic efficacy and safety of a new transdermal fentanyl patch compared to standard opioid treatment in cancer pain

A new 72-hour transdermal fentanyl matrix patch has been designed, which has a 35%-50% reduction of the absolute fentanyl content compared with other currently available transdermal fentanyl patches that are using the matrix technology. The new patch has previously been shown to be pharmacokinetically bioequivalent to the marketed fentanyl patch. To determine noninferiority in efficacy in cancer patients and to compare safety, a clinical trial comparing the new fentanyl patch with standard oral or transdermal opioid treatment was planned. The design was an open, parallel group, multicenter trial, in which 220 patients were randomized to receive either the fentanyl patch or standard opioid treatment for 30 days. The primary efficacy variable, pain intensity (PI) on a 0-10-point numerical rating scale, was recorded once daily. The primary endpoint was the relative area under the curve of PI expressed as a percentage of the maximum possible PI area under the curve. Any adverse events were recorded; four tolerability endpoints, constipation, nausea, daytime drowsiness, and sleeping disturbances, were assessed daily. Noninferiority was shown; the upper 95% confidence interval limits of the mean difference in relative PI area under the curve between the fentanyl patch and standard opioid treatment were less than 10% for both the intention-to-treat and per-protocol populations. Scores for the tolerability endpoints were similar in the treatment groups. The new fentanyl matrix patch with a lower drug load was found noninferior and as safe as established standard oral and transdermal opioid treatment.

Transdermal treatment options for neurological disorders: impact on the elderly

As people grow old, their need for medications increases dramatically because of the higher incidence of chronic pain, diabetes mellitus, cardiovascular and neurological diseases in the elderly population. Furthermore, the elderly require special consideration with respect to drug delivery, drug interactions and adherence. In particular, patients with chronic neurological diseases often require multiple administration of drugs during the day to maintain constant plasma medication levels, which in turn increases the likelihood of poor adherence. Consequently, several attempts have been made to develop pharmacological preparations that can achieve a constant rate of drug delivery. For example, transdermal lisuride and apomorphine have been shown to reduce motor fluctuations and duration of 'off' periods in advanced Parkinson's disease, while rotigotine allows significant down-titration of levodopa without severe adverse effects. Thus, parkinsonian patients with long-term levodopa syndrome or motor disorders during sleep could benefit from use of transdermal lisuride and apomorphine. Moreover, transdermal dopaminergic drugs, particularly rotigotine, seem the ideal treatment for patients experiencing restless legs syndrome or periodic limb movement disorder during sleep, disorders that are quite common in elderly people or in association with neurodegenerative diseases. Unlike dopaminergic drugs, transdermal treatments for the management of cognitive and behavioural dysfunction in patients with Parkinson's disease and Alzheimer's disease have inconsistent effects and no clearly established role. Nevertheless, because of their favourable pharmacological profile and bioavailability, the cholinesterase inhibitors tacrine and rivastigmine are expected to show at least the same benefits as oral formulations of these drugs, but with fewer severe adverse effects. Transdermal delivery systems play an important role in the management of neuropathic pain. The transdermal lidocaine (lignocaine) patch is recommended as first-line therapy for the treatment of postherpetic neuralgia. Furthermore, in patients with severe persistent pain, transdermal delivery systems using the opioids fentanyl and buprenorphine are able to achieve satisfactory analgesia with good tolerability, comparable to the benefits seen with oral formulations. Transdermal administration is the ideal therapeutic approach for chronic neurological disorders in elderly people because it provides sustained therapeutic plasma levels of drugs, is simple to use, and may reduce systemic adverse effects. Several transdermal delivery systems are currently under investigation for the treatment of Parkinson's disease, Alzheimer's disease and neuropathic pain. Although most transdermal delivery systems treatments cannot be considered as first-line therapy at present, some of them provide clear advantages compared with other routes of administration and may become the preferred treatment in selected patients. In general, however, most transdermal treatments still require long-term evaluation in large patient groups in order to optimise dosages and evaluate the actual incidence of local and systemic adverse effects.

Enhancement of transdermal delivery of theophylline using microemulsion vehicle

A microemulsion vehicle had been studied as a possible matrix for transdermal delivery of theophylline. The existence of microemulsion regions were investigated in pseudo-ternary phase diagrams, and various microemulsion formulations were prepared using oleic acid, Cremophor RH40/Labrasol (1:2) and water. The optimal formulation of the microemulsion was evaluated in vitro using Franz diffusion cells. The droplet size of microemulsion was characterized by photo correlation spectroscopy. Pharmacokinetic study in vivo was conducted using rabbits, and the results indicated that AUC(0-->infinity) of transdermal administration was 1.65-fold higher than that of oral solution administration. These studies showed that microemulsion system of theophylline might be promising vehicles for the transdermal delivery of theophylline.

Identification of exposure pathways for opioid narcotic analgesics in pharmaceutical production workers

The protection of workers from the potential harmful effects of active pharmaceutical ingredients (APIs) poses a significant challenge for the drug manufacturing industry. The actual pathways through which pharmaceutical production workers are exposed to potent drugs and the processes resulting in actual uptake are up till now virtually unknown. In this study, a detailed exposure assessment survey was conducted in a pharmaceutical 'primary manufacturing' production facility during which environmental and biological exposure monitoring for potent opioid narcotic drugs was performed. On the occasion of multiple consecutive production days, personal half-shift air samples were collected and hand wipes were taken at the end of each half-shift and analysed for fentanyl. All environmental samples showed detectable amounts of fentanyl (>0.1 ng per sample), indicating a potential for both inhalation and dermal exposure. Spatial distribution of fentanyl dermal contamination was further investigated by means of patch samplers placed on five anatomical regions of the body. Body locations showing the highest level of fentanyl contamination were identified as the hands, the neck and lower arms. The effective uptake of fentanyl was demonstrated by the detection of this opioid in urine samples of the workers involved. Individual and group-level analysis of combined external and internal fentanyl exposure measures revealed a positive and significant correlation between fentanyl hand exposure and urinary excretion, while it seemed that the effect of inhalation exposure was largely due to its correlation with dermal exposure. The results of the established individual linear and mixed effects models strongly suggest that in most workers the dermal pathway is actually the primary route of fentanyl exposure.

Controlled systemic delivery of indomethacin using membrane-moderated, cream formulation-based transdermal devices

The present study was carried out to design a viable and practically effective transdermal systems of indomethacin using cream-based drug reservoirs and suitable rate controlling membranes. As vehicles, a more lipophilic base (F(1)) and a cream formulation containing predominant aqueous phase (F(2)) were chosen to study the influence of vehicle nature and role of permeation enhancers that increases thermodynamic activity and to provide diffusible species of drug to skin. Rate controlling membranes of cellulose acetate (CA) and ethyl cellulose (EC) with polyvinyl pyrollidine and hydroxypropyl methyl cellulose were used to design transdermal devices. In vivo, effective plasma concentrations of indomethacin are maintained up to 24 hr whereas oral formulation showed only up to 8 hr. Although the plasma drug levels between both EC films differ insignificantly, PVP film showed a better pharmacokinetic profile. The pharmacodynamic performance of the transdermal devices exhibited good anti-inflammatory activity over 24 hr compared with orally administered indomethacin. In vivo studies indicate the superiority of CA films over the EC films. Further, enhancement may be achieved with other classic enhancers/enhancement strategies with such devices containing aqueous cream vehicle and the optimum membranes.

Pharmacokinetics and pharmacodynamics in clinical use of scopolamine

The alkaloid L-(-)-scopolamine [L-(-)-hyoscine] competitively inhibits muscarinic receptors for acetylcholine and acts as a nonselective muscarinic antagonist, producing both peripheral antimuscarinic properties and central sedative, antiemetic, and amnestic effects. The parasympatholytic scopolamine, structurally very similar to atropine (racemate of hyoscyamine), is used in conditions requiring decreased parasympathetic activity, primarily for its effect on the eye, gastrointestinal tract, heart, and salivary and bronchial secretion glands, and in special circumstances for a CNS action. Therefore, scopolamine is most suitable for premedication before anesthesia and for antiemetic effects. This alkaloid is the most effective single agent to prevent motion sickness. Scopolamine was the first drug to be made commercially available in a transdermal therapeutic system (TTS-patch) delivering alkaloid. Recently, pharmacokinetic data on scopolamine in different biozlogic matrices were obtained most efficiently using liquid chromatographic-tandem mass spectrometric (LC-MS/MS) or gas chromatography online coupled to mass spectrometry. Pharmacokinetic parameters are dependent on the dosage form (oral dose, tablets; parenteral application; IV infusion; SC and IM injection). Scopolamine has a limited bioavailability if orally administered. The maximum drug concentration occurs approximately 0.5 hours after oral administration. Because only 2.6% of nonmetabolized L-(-)-scopolamine is excreted in urine, a first-pass metabolism is suggested to occur after oral administration of scopolamine. Because of its short half-life in plasma and dose-dependent adverse effects (in particular hallucinations and the less serious reactions, eg, vertigo, dry mouth, drowsiness), the clinical use of scopolamine administered orally or parenterally is limited. To minimize the relatively high incidence of side effects, the transdermal dosage form has been developed. The commercially available TTS-patch contains a 1.5-mg drug reservoir and a priming dose (140 microg) to reach the steady-state concentration of scopolamine quickly. The patch releases 0.5 mg alkaloid over a period of 3 days (releasing rate 5 microg/h). Following the transdermal application of scopolamine, the plasma concentrations of the drug indicate major interindividual variations. Peak plasma concentrations (Cmax) of approximately 100 pg/mL (range 11-240 pg/mL) of the alkaloid are reached after about 8 hours and achieve steady state. During a period of 72 hours the plaster releases scopolamine, so constantly high plasma levels (concentration range 56-245 pg/mL) are obtained, followed by a plateau of urinary scopolamine excretion. Although scopolamine has been used in clinical practice for many years, data concerning its metabolism and the renal excretion in man are limited. After incubation with beta-glucuronidase and sulfatase, the recovery of scopolamine in human urine increased from 3% to approximately 30% of the drug dose (intravenously administered). According to these results from enzymatic hydrolysis of scopolamine metabolites, the glucuronide conjugation of scopolamine could be the relevant pathway in healthy volunteers. However, scopolamine metabolism in man has not been verified stringently. An elucidation of the chemical structures of the metabolites extracted from human urine is still lacking. Scopolamine has been shown to undergo an oxidative demethylation during incubation with CYP3A (cytochrome P-450 subfamily). To inhibit the CYP3A located in the intestinal mucosa, components of grapefruit juice are very suitable. When scopolamine was administered together with 150 mL grapefruit juice, the alkaloid concentrations continued to increase, resulting in an evident prolongation of tmax (59.5 +/- 25.0 minutes; P < 0.001). The AUC0-24h values of scopolamine were higher during the grapefruit juice period. They reached approximately 142% of the values associated with the control group (P < 0.005). Consequently, the related absolute bioavailabilities (range 6% to 37%) were significantly higher than the corresponding values of the drug orally administered together with water (range 3% to 27%). The effect of the alkaloid on quantitative electroencephalogram (qEEG) and cognitive performance correlated with pharmacokinetics was shown in studies with healthy volunteers. From pharmacokinetic-pharmacodynamic modeling techniques, a direct correlation between serum concentrations of scopolamine and changes in total power in alpha-frequency band (EEG) in healthy volunteers was provided. The alkaloid readily crosses the placenta. Therefore, scopolamine should be administered to pregnant women only under observation. The drug is compatible with nursing and is considered to be nonteratogenic. In conclusion, scopolamine is used for premedication in anesthesia and for the prevention of nausea and vomiting associated with motion sickness. Pharmacokinetics and pharmacodynamics of scopolamine depend on the dosage form. Effects on different cognitive functions have been extensively documented.

Switching from reservoir to matrix systems for the transdermal delivery of fentanyl: a prospective, multicenter pilot study in outpatients with chronic pain

Matrix systems for transdermal fentanyl will replace the reservoir systems in Europe. In an industry-independent, prospective, multicenter pilot study, 46 outpatients with chronic pain were asked to assess pain intensity, sleep interference, adverse events, and multiple secondary parameters during administration of the last reservoir and the first two matrix patches. There was no difference in pain intensity, sleep interference, and the rate of adverse events between both systems. Self assessment on a 6-step numeric rating scale (1 = very good, 6 = insufficient) comparing the two systems (reservoir vs. matrix) showed that skin compatibility (2.6 vs. 1.5), adhesive properties (3.2 vs. 1.8), wearability/comfort (2.8 vs. 1.5), and general satisfaction (2.5 vs. 1.8) improved significantly with the new matrix technology. At study endpoint, 91% of patients preferred the matrix system for future use. The new fentanyl matrix system is characterized by a high level of general satisfaction, ease of use, patient acceptance, and improved skin compatibility. Reservoir and matrix systems appear to have comparable efficacy and safety so that outpatients can be switched directly from the reservoir to the matrix system without difficulties and new dose titration.

Omeprazole Absorption from a Compounded Transdermal Formulation in Healthy Volunteers

OBJECTIVE

To evaluate the plasma concentration versus time profile of omeprazole following the administration of a compounded transdermal gel formulation in healthy volunteers.

DESIGN

Single-dose transdermal pharmacokinetic (PK) study including a comparison with historical data from an oral PK study.

SETTING

Academic clinical research center.

PARTICIPANTS

Eight healthy volunteers between 18 and 50 years of age.

INTERVENTIONS

Omeprazole gel 40 mg (0.8 mL) was applied to the ventral surface of the forearm covering an area of 7 x 15 cm without an occlusive dressing. Blood samples were collected just before application and then at 1, 2, 3, 4, 6, and 8 hours. Plasma concentrations of omeprazole were determined using a validated liquid chromatography tandem mass spectrometry method.

MAIN OUTCOME MEASURES

PK parameters (maximal plasma concentration [C(max)], the time of C(max), [T(max)], the area under the omeprazole concentration versus time curve from 0 to 8 hours, the elimination rate constant, and the half-life of the elimination phase) following transdermal administration, compared with historical controls who had received an oral omeprazole 40 mg dose during a previous study.

RESULTS

Of the eight volunteers, five had undetectable plasma omeprazole concentrations throughout the 8-hour study, precluding a complete PK analysis. For the three volunteers with detectable plasma omeprazole concentrations, the values ranged from 0.204 to 0.552 ng/mL. Including values of 0 for the patients with undetectable levels, the mean (+/- SD) C(max) was 0.153 +/- 0.241 ng/mL, and the T(max) in patients with detectable levels occurred at approximately 6 hours. The plasma concentrations following transdermal administration were approximately 1,000-fold lower than those observed with oral dosing.

CONCLUSION

Transdermal absorption from a single dose of the omeprazole gel formulation used in this study was poor. This transdermal gel formulation is clearly not bioequivalent to the oral capsule.

Safety, Tolerability, and Efficacy of Continuous Transdermal Dopaminergic Stimulation with Rotigotine Patch in Early-Stage Idiopathic Parkinson Disease

Rotigotine is a new dopamine agonist with transdermal patch formulation for the treatment of Parkinson disease. The aim of this study was to investigate safety and efficacy of rotigotine in patients with early-stage Parkinson disease. In this open-label, dose-escalation, safety and efficacy study, 31 patients in the early stages of idiopathic Parkinson disease received rotigotine to a maximum of 18.0 mg/day. Of the 29 patients who completed the 28-day treatment phase, 24 were maintained at the maximum dose level. The drug was well tolerated, and skin reactions were mild. A statistically significant improvement in UPDRS I, II, and III scores was observed from baseline to end of treatment for the 29 subjects who completed the trial. Mean improvement (+/- standard deviation) was -0.41 +/- 0.78 on UPDRS I (P = 0.0078), -2.76 +/- 3.31 on UPDRS II (P = 0.0001), and -4.62 +/- 5.32 on UPDRS III (P < 0.0001). When results were stratified by maximum dose achieved, significant improvements were seen on all 3 subscores for patients achieving the maximum dose. These data suggest that rotigotine is a safe, well-tolerated, and effective treatment for early-stage Parkinson disease.

Transdermal delivery of naloxone: skin permeation, pharmacokinetic, irritancy and stability studies

The current investigation aims to evaluate ex vivo, in vivo performance, stability and irritancy potential of a transdermal formulation of naloxone (NLX) developed at our laboratory at different concentrations (10, 20 and 30mg/g of gel) in a transdermal reservoir patch. Ex vivo permeation studies were performed by employing porcine and rat skins. In vivo performance was assessed in Sprague-Dawley rats by single and multiple application of the patch. Further stability of the formulation was established for 3 months at accelerated stability conditions as per ICH guidelines. Amongst the barriers used the rat skin was found to be more permeable than the porcine epidermis and the flux across each barrier increased with increasing thermodynamic activity of drug in the gel. Based on ex vivo data, the surface area (SA) of the patch was predicted to be 39.6 cm(2) in order to achieve therapeutic blood levels. Upon single dose administration, the steady-state levels were maintained from 4-48 h, which proves the clear advantage of transdermal delivery system over the current mode of administration, i.e., intravenous (i.v.) bolus which is effective upto a maximum of 1.5h. Upon multiple dose administration, the sustained steady state for 12h, even after patch removal proves the formation of drug depot in the skin. The formulations were found to be stable with respect to NLX assay and penetration enhancer efficacy upto 3 months under accelerated stability conditions. The alteration of penetration barrier function, as evidenced by increased trans epidermal water loss (TEWL) was not accompanied by any significant amount of skin irritation measured using laser doppler velocimetry (LDV). The developed transdermal delivery system of NLX is efficacious, stable and safe upon single and multiple dose applications each lasting for 48 h.

Drug delivery across the skin

Since the introduction of the first through the skin (TTS) therapeutic in 1980, a total of 34 TTS products have been marketed and numerous drugs have been tested by more than 50 commercial organisations for their suitability for TTS delivery. Most of the agents which have been tested have had low molecular weights, due to the impermeability of the skin barrier. This barrier resides in the outermost skin layer, the stratum corneum. It is mechanical, anatomical, as well as chemical in nature; laterally overlapping cell multi-layers are sealed by tightly packed, intercellular, lipid multi-lamellae. Chemical skin permeation enhancers increase the transport across the barrier by partly solubilising or extracting the skin lipids and by creating hydrophobic pores. This is often irritating and not always well-tolerated. The TTS approach allows drugs (< 400 kDa in size) to permeate through the resulting pores in the skin, with a short lag-time and subsequent steady-state period. Drug bioavailability for TTS delivery is typically below 50%, avoiding the first pass effect. Wider, hydrophilic channels can be generated by skin poration, with the aid of a small electrical current (> 0.4 mA/cm2) across the skin (iontophoresis) or therapeutic ultrasound (few W/cm2; sonoporation). High-voltage (> 150 V, electroporation) widens the pores even more and often irreversibly. These standard poration methods require experience and equipment and are therefore, not practical; at best, charged/small molecules (< or = 4000 kDa in size) can be delivered efficiently across the skin. In spite of the potential harm of gadget-driven skin poration, this method is used to deliver molecules which conventional TTS patches are unable to deliver, especially polypeptides. Lipid-based drug carriers (liposomes, niosomes, nanoparticle microemulsions, etc.) were proposed as alternative, low-risk delivery vehicles. Such suspensions provide an improved drug reservoir on the skin, but the aggregates remain confined to the surface. Conventional carrier suspensions increase skin hydration and/or behave as skin permeation enhancers. The recently developed carriers; Transferomes, comprise pharmaceutically-acceptable, established compounds and are thought to penetrate the skin barrier along the naturally occurring transcutaneous moisture gradient. Transfersomes are believed to penetrate the hydrophilic (virtual) channels in the skin and widen the former after non-occlusive administration. Both small and large hydrophobic and hydrophilic molecules are deliverable across the stratum after conjugation with Transfersomes. Drug distribution after transdermal delivery probably proceeds via the lymph. This results in quasi-zero order kinetics with significant systemic drug levels reached after a lag-time of up to a few hours. The relative efficiency of TTS drug delivery with Transfersomes is typically above 50 %; with the added possibility of regional drug targeting.

Transdermal delivery of imipramine hydrochloride: Development and evaluation (in vitro andin vivo) of reservoir gel formulation

The in vitro permeation studies of imipramine hydrochloride (IMH) reported earlier from our laboratory showed that a combination of menthol (2.5% w/v) and oleic acid (2.5% w/v) worked well in terms of safety and efficacy. The main objective of this study was to evaluate the in vivo performance of this combination; in order to do that, penetration enhancers were incorporated in a hydro-alcoholic gel of hydroxypropylmethyl cellulose along with IMH and used as the drug matrix in a reservoir transdermal patch. A stability study of IMH gel was performed at 40 degrees C/75% RH for 2 months. The results of this study indicate that gels of IMH stored at 40 degrees C/75% RH turned yellow brown in 2 months and the small change in viscosity of gel at 40 degrees C/75% RH had an insignificant effect on the release rate of IMH from the gel (p>0.05). The in vivo performance of the gel was tested in rats using a reservoir transdermal patch, which consisted of a backing membrane, drug matrix and retaining membrane with an area of 12.5 cm2. Plasma concentrations of 3 microg/ml of IMH were achieved and in a histopathological study 24 h occlusion was found to be safe.

Formulation design of double-layer in the outer shell of dry-coated tablet to modulate lag time and time-controlled dissolution function: studies on micronized ethylcellulose for dosage form design (VII)

The dry-coated tablet with optimal lag time was designed to simulate the dosing time of drug administration according to the physiological needs. Different compositions of ethylcellulose (EC) powder with a coarse particle (167.5 microm) and several fine particles (< 6 microm), respectively, were mixed to formulate the whole layer of the outer shell of dry-coated tablets. The formulations containing different weight ratios of coarse/fine particles of EC powders or 167.5 microm EC powder/excipient in the upper layer of the outer shell to influence the release behavior of sodium diclofenac from dry-coated tablet were also explored. The results indicate that sodium diclofenac released from all the dry-coated tablets exhibited an initial lag period, followed by a stage of rapid drug release. When the mixture of the coarse/fine particles of EC powders was incorporated into the whole layer, the lag time was almost the same. The outer shell broke into 2 halves to make a rapid drug release after the lag time, which belonged to the time-controlled disruption of release mechanism. When the lower layer in the outer shell was composed of 167.5 microm EC powder and the upper layer was formulated by mixing different weight ratios of 167.5 microm and 6 microm of EC powders, the drug release also exhibited a time-controlled disruption behavior. Its lag time might be freely modulated, depending on the amount of 6 microm EC powder added. Once different excipients were respectively incorporated into the upper layer of the outer shell, different release mechanisms were observed as follows: time-controlled explosion for Explotab, disruption for Avicel and spray-dried lactose, erosion for dibasic calcium phosphate anhydrate, and sigmoidal profile for hydroxypropyl methylcellulose.

Pharmacokinetic Profile and Efficacy of a Fentanyl Transdermal Delivery System for Acute Postoperative Pain after Intra-abdominal Gynecologic Surgery for Cancer

PURPOSE

This prospective, randomized, single-blind study evaluated the efficacy and pharmacokinetic profile of a transdermal delivery system for fentanyl to provide relief of acute postoperative pain in patients undergoing intra-abdominal gynecologic surgery for cancer.

METHODS

Forty female patients were randomized to either transdermal fentanyl 50 microg/hour (n = 20) or transdermal placebo (n = 20). Transdermal systems were placed 1 hour preoperatively and removed 25 hours later. Pain control was supplemented with a nonopioid drug, bupivacaine 0.125-0.25%, administered through an epidural catheter via patient-controlled epidural analgesia. Serum fentanyl concentrations, bupivacaine consumption, pain scores [visual analog scale (VAS)], sedation rating score, adverse events, and physiological parameters were recorded for 48 hours postoperatively.

RESULTS

The minimum effective concentration of fentanyl in serum (0.63 ng/mL) was achieved at 11.3 +/- 4.9 hours after application, and serum concentrations remained above this level until 13 hours after removal. The TTS-F group had lower VAS pain scores and a significant 66% reduction in utilization of bupivacaine compared with placebo. Pain scores were significantly correlated with serum fentanyl concentration (P = 0.025). All physiological parameters fluctuated within normal range and no differences were observed between treatments. Adverse events were similar between the groups with only the incidence of local erythema significantly higher in the TTS-F group (30% vs. 5%, P < 0.05), and sedation scores were significantly higher in the TTS-F group during the immediate postoperative period.

CONCLUSION

The transdermal therapeutic system for administration of fentanyl, combined with epidural administration of a nonopioid analgesic such as bupivacaine is effective in controlling postoperative pain after gynecologic surgery. Additionally, the safety/tolerability of this regimen was similar to placebo plus bupivacaine.

Transdermal buprenorphine

Buprenorphine is a low molecular weight, lipophilic, opioid analgesic. Recently, a transdermal matrix patch formulation of buprenorphine has become available in three dosage strengths designed to release buprenorphine at 35, 52.5 and 70 micro g/h over a 72-hour period. At least satisfactory analgesia with minimal requirement for rescue medication (</=0.2 mg/day sublingual buprenorphine) was achieved by 34-50% of patients with chronic pain treated with transdermal buprenorphine 35, 52.5 or 70 micro g/h and 31% of placebo recipients, in one double-blind, placebo-controlled, randomised trial. In one trial involving patients unsuccessfully treated with weak opioids or morphine, 36.6% and 47.5% of buprenorphine 35 micro g/h and 52.5 micro g/h recipients, respectively, experienced at least satisfactory analgesia and received </=0.2 mg/day of sublingual buprenorphine compared with 16.2% of placebo recipients (both p </= 0.032). The requirement for rescue medication was reduced from baseline in >50% of patients treated with transdermal buprenorphine, in two trials. Furthermore, despite the availability of rescue medication to all patients, those receiving transdermal buprenorphine tended to experience greater pain relief, reduced pain intensity and longer pain-free sleep. Transdermal buprenorphine was generally well tolerated. Systemic adverse events were typical of opioid treatment or were attributable to the underlying disease.

Feline penile erection induced by topical glans penis application of combination alprostadil and SEPA (Topiglan)

The objective of this study was to evaluate the efficacy of topically applied prostaglandin E1 (PGE(1))+5% SEPA (soft enhancement of percutaneous absorption) on the glans penis in a feline erection model. Erectile response after glans penis administration of PGE(1)+5% SEPA cream (Topiglan, MacroChem Co., Lexington, MA, USA) was compared to the erectile response after intracavernosal administration of the triple-drug combination (1.65 mg papaverine, 25 microg phentolamine, and 0.5 microg PGE(1)). The placebo cream and increasing concentrations (0.25%, 2.5 mg/ml; 0.5%, 5 mg/ml; and 1%, 10 mg/ml) of PGE(1)+5% SEPA were applied in a total volume of 0.1 ml via a plastic needle-less syringe. The control triple-drug combination was administrated intracavernosally via a 30-gauge needle at the completion of each experiment to serve as a control reference. With each application of placebo, PGE(1)+SEPA, and the triple-drug combination, changes in intracavernosal pressure and systemic blood pressure were continuously monitored. Topical application of PGE(1)+SEPA induced increases in intracavernosal pressure in a dose-dependent manner, with minimal effects on systemic blood pressure. The increases obtained with 1% PGE(1) Topiglan cream were similar to the intracavernosal pressure values elicited by the standard intracavernosal triple-drug combination. These data demonstrate that topical glans penis application of PGE(1)+SEPA can induce an erectile response in cats with minimal systemic adverse effects. Oral pharmacological agents are the first-line treatment for male ED. Studies investigating the effectiveness of noninvasive modalities such as topical therapy should continue, because these agents have the potential to avoid the systemic effects commonly seen with oral therapies. Additionally, topical therapy may also benefit patients who are unresponsive to oral agents or have explicit contraindications. Topical PGE(1) application to the glans penis may become an important treatment option in selected patients suffering from erectile dysfunction.