A review of the clinical pharmacokinetics of opioids, benzodiazepines, and antimigraine drugs delivered intranasally

Demystifying the potential of lipid-based nanocarriers in targeting brain malignancies

Drug targeting for brain malignancies is restricted due to the presence of the blood-brain barrier (BBB) and blood-brain tumor barrier (BBTB), which act as barriers between the blood and brain parenchyma. Certainly, the limited therapeutic options for brain malignancies have made notable progress with enhanced biological understanding and innovative approaches, such as targeted therapies and immunotherapies. These advancements significantly contribute to improving patient prognoses and represent a promising shift in the landscape of brain malignancy treatments. A more comprehensive understanding of the histology and pathogenesis of brain malignancies is urgently needed. Continued research focused on unraveling the intricacies of brain malignancy biology holds the key to developing innovative and tailored therapies that can improve patient outcomes. Lipid nanocarriers are highly effective drug delivery systems that significantly improve their solubility, bioavailability, and stability while also minimizing unwanted side effects. Surface-modified lipid nanocarriers (liposomes, niosomes, solid lipid nanoparticles, nanostructured lipid carriers, lipid nanocapsules, lipid-polymer hybrid nanocarriers, lipoproteins, and lipoplexes) are employed to improve BBB penetration and uptake through various mechanisms. This systematic review illuminates and covers various topics related to brain malignancies. It explores the different methods of drug delivery used in treating brain malignancies and delves into the benefits, limitations, and types of brain-targeted lipid-based nanocarriers. Additionally, this review discusses ongoing clinical trials and patents related to brain malignancy therapies and provides a glance into future perspectives for treating this condition.

The Safety of High-Dose Intranasal Fentanyl in the Pediatric Emergency Department

OBJECTIVES

This study aimed to determine if the use of intranasal (IN) fentanyl in the pediatric emergency department of 2 to 5 μg/kg at doses greater than 100 μg is associated with adverse events in pediatric patients.

METHODS

We performed a retrospective chart review of patients receiving IN fentanyl at an urban, tertiary care emergency department in Memphis, TN, from January 1, 2011, to December 31, 2017. All adverse events documented through the hospital's voluntary safety reporting system involving IN fentanyl were reviewed to determine patient outcomes.

RESULTS

A total of 3205 patients received greater than 100 μg of IN fentanyl during the study period from 2011 to 2017. The average (SD) patient age was 13.7 (2.65) years, ranging from 5 to 18 years. The mean (SD) initial dose was 162 (30) μg ranging from 102 to 265 μg (2 doses were given greater than 200 μg in the study period). Initial average (SD) dose for weight was 2.62 (0.5) μg/kg. A total of 13 adverse events were documented, with only 3 occurring at doses greater than 100 μg. No patients required the reversal agent naloxone or invasive respiratory support.

CONCLUSIONS

To our knowledge, this is the first study using doses greater than 100 μg of IN fentanyl in a pediatric population. Our results indicate that fentanyl can be safely administered at doses of greater than 100 μg without any clinically significant adverse outcomes observed for 7 years of use. It is our hope that this information will increase utilization of IN fentanyl for treatment of acute pain in emergency departments and in the prehospital setting.

Mucoadhesive and mucus-penetrating interpolyelectrolyte complexes for nose-to-brain drug delivery

Nasal administration offers a possibility of delivering drugs to the brain. In the present work, nasal drug delivery systems were designed based on cationic Eudragit® EPO (EPO) and anionic Eudragit® L100-55 (L100-55) methacrylate copolymers. Two types of nanocarriers were prepared using interpolyelectrolyte complexation between these polymers. The first type of nanoparticles was prepared by forming interpolyelectrolyte complexes between unmodified EPO and L100-55. The second type of nanoparticles was formed through the complexation between PEGylated L100-55 and EPO. For this purpose, PEGylated L100-55 was synthesized by chemical conjugation of L100-55 with O-(2-aminoethyl)polyethylene glycol. The mucoadhesive properties of these nanoparticles were evaluated ex vivo using sheep nasal mucosa. Nanoparticles based on EPO and L100-55 exhibited mucoadhesive properties towards nasal mucosa, whereas PEGylated nanoparticles were non-mucoadhesive hence displayed mucus-penetrating properties. Both types of nanoparticles were used to formulate haloperidol and their ability to deliver the drug to the brain was evaluated in rats in vivo.

Time Is Brain: Acute Control of Repetitive Seizures and Status Epilepticus Using Alternative Routes of Administration of Benzodiazepines

Time plays a major role in seizure evaluation and treatment. Acute repetitive seizures and status epilepticus are medical emergencies that require immediate assessment and treatment for optimal therapeutic response. Benzodiazepines are considered the first-line agent for rapid seizure control. Thus, various routes of administration of benzodiazepines have been studied to facilitate a quick, effective, and easy therapy administration. Choosing the right agent may vary based on the drug and route properties, patient’s environment, caregiver’s skills, and drug accessibility. The pharmacokinetic and pharmacodynamic aspects of benzodiazepines are essential in the decision-making process. Ultimately, agents and routes that give the highest bioavailability, fastest absorption, and a modest duration are preferred. In the outpatient setting, intranasal and buccal routes appear to be equally effective and more rapidly administered than rectal diazepam. On the other hand, in the inpatient setting, if available, the IV route is ideal for benzodiazepine administration to avoid any potential absorption delay. In this article, we will provide an overview and comparison of the various routes of benzodiazepine administration for acute control of repetitive seizures and status epilepticus.

Nanomaterial-based blood-brain-barrier (BBB) crossing strategies

Increasing attention has been paid to the diseases of central nervous system (CNS). The penetration efficiency of most CNS drugs into the brain parenchyma is rather limited due to the existence of blood-brain barrier (BBB). Thus, BBB crossing for drug delivery to CNS remains a significant challenge in the development of neurological therapeutics. Because of the advantageous properties (e.g., relatively high drug loading content, controllable drug release, excellent passive and active targeting, good stability, biodegradability, biocompatibility, and low toxicity), nanomaterials with BBB-crossability have been widely developed for the treatment of CNS diseases. This review summarizes the current understanding of the physiological structure of BBB, and provides various nanomaterial-based BBB-crossing strategies for brain delivery of theranostic agents, including intranasal delivery, temporary disruption of BBB, local delivery, cell penetrating peptide (CPP) mediated BBB-crossing, receptor mediated BBB-crossing, shuttle peptide mediated BBB-crossing, and cells mediated BBB-crossing. Clinicians, biologists, material scientists and chemists are expected to be interested in this review.

One should avoid retro-orbital pharmacokinetic sample collections for intranasal dosing in rats: Illustration of spurious pharmacokinetics generated for anti-migraine drugs zolmitriptan and eletriptan

Because of the avoidance of first pass metabolic effects due to direct and rapid absorption with improved permeability, intranasal route represents a good alternative for extravascular drug administration. The aim of the study was to investigate the intranasal pharmacokinetics of two anti-migraine drugs (zolmitriptan and eletriptan), using retro-orbital sinus and jugular vein sites sampling. In a parallel study design, healthy male Sprague-Dawley (SD) rats aged between 8 and 12weeks were divided into groups (n=4 or 5/group). The animals of individual groups were dosed intranasal (~1.0mg/kg) and oral doses of 2.1mg/kg of either zolmitriptan or eletriptan. Serial blood sampling was performed from jugular vein or retro-orbital site and plasma samples were analyzed for drug concentrations using LC-MS/MS assay. Standard pharmacokinetics parameters such as T_max, C_max, AUC_last, AUC_0-inf and T_1/2 were calculated and statistics of derived parameters was performed using unpaired t-test. After intranasal dosing, the mean pharmacokinetic parameters C_max and AUC_inf of zolmitriptan/eletriptan showed about 17-fold and 3-5-fold higher values for retro-orbital sampling as compared to the jugular vein sampling site. Whereas after oral administration such parameters derived for both drugs were largely comparable between the two sampling sites and statistically non-significant. In conclusion, the assessment of plasma levels after intranasal administration with retro-orbital sampling would result in spurious and misleading pharmacokinetics.

Intranasal fentanyl for initial treatment of vaso-occlusive crisis in sickle cell disease

BACKGROUND

Analgesia administration for children with vaso-occlusive crises is often delayed in the emergency department. Intranasal fentanyl (INF) has been shown to be safe and effective in providing rapid analgesia for other painful conditions. Our objective was to determine if children with a vaso-occlusive crisis (VOC) who received initial treatment with INF compared to placebo achieved a greater decrease in pain score after 20 min.

PROCEDURE

This was a randomized, double-blind, placebo-controlled trial. Children with sickle cell disease, 3-20 years old, not taking daily opiates were eligible for the study. Subjects who presented to the emergency department with a pain score ≥6 were randomized to either a single dose of INF (2 μg/kg, maximum 100 μg) or an equivalent volume of intranasal saline. Pain scores were obtained using a modified Wong-Baker FACES pain scale prior to the administration of study drug and at 10, 20, and 30 min afterward. Additional analgesic medication was given per standard protocol.

RESULTS

Forty-nine subjects completed the study (24 fentanyl and 25 placebo). Subjects who received INF had a greater decrease in median pain score at 20 min compared to placebo (2 [interquartile range, (IQR) 0.5-4] vs. 1 [IQR 0-2], P = 0.048), but not at 10 or 30 min. There were no serious adverse events in either group.

CONCLUSION

Children who received INF had a greater decrease in pain score at 20 min compared to those who received placebo. Further studies should evaluate how to best incorporate INF into the emergency care of a child with a VOC.

Strategies for transporting nanoparticles across the blood-brain barrier

The existence of blood-brain barrier (BBB) hampers the effective treatment of central nervous system (CNS) diseases. Almost all macromolecular drugs and more than 98% of small molecule drugs cannot pass the BBB. Therefore, the BBB remains a big challenge for delivery of therapeutics to the central nervous system. With the structural and mechanistic elucidation of the BBB under both physiological and pathological conditions, it is now possible to design delivery systems that could cross the BBB effectively. Because of their advantageous properties, nanoparticles have been widely deployed for brain-targeted delivery. This review paper presents the current understanding of the BBB under physiological and pathological conditions, and summarizes strategies and systems for BBB crossing with a focus on nanoparticle-based drug delivery systems. In summary, with wider applications and broader prospection the treatment of brain targeted therapy, nano-medicines have proved to be more potent, more specific and less toxic than traditional drug therapy.

Comparative Effectiveness of Intranasal Dexmedetomidine-Midazolam versus Oral Chloral Hydrate Targeting Moderate Sedation during Pediatric Transthoracic Echocardiograms

Objective  To compare efficacy and safety of two moderate sedation regimens for transthoracic echocardiography (TTE): intranasal dexmedetomidine-midazolam (DM) versus oral chloral hydrate (CH) syrup. Method  This was a retrospective cohort of 93 children under 4 years of age receiving moderate sedation with either DM or CH for TTE from January 2011 through December 2014. Measurements and Main Results  Forty-nine patients received oral CH and 44 received the intranasal combination of DM. The demographics between groups were similar except the DM patients were slightly older and heavier (each p  < 0.05). Failure rate between groups did not reach statistical significance (CH 14.3% vs. DM 6.8%; p  = 0.324). Total sedation to discharge time was similar between groups (CH 89.4 minutes vs. DM 89.6 minute; p  = 0.97). Cardiopulmonary data did reveal a significantly lower heart rate (101.9 vs. 91.7; p  < 0.001) and respiratory rate (23.4 vs. 21.0, p  = 0.03) in the DM group, but no difference in blood pressure measurements or echo determined shortening fraction. Conclusion  These data support the use of intranasal DM as a safe and efficacious method of moderate sedation for children undergoing TTE.

Intranasal ketamine for acute traumatic pain in the Emergency Department: a prospective, randomized clinical trial of efficacy and safety

BACKGROUND

Ketamine has been well studied for its efficacy as an analgesic agent. However, intranasal (IN) administration of ketamine has only recently been studied in the emergency setting. The objective of this study was to elucidate the efficacy and adverse effects of a sub-dissociative dose of IN Ketamine compared to IV and IM morphine.

METHODS

A single-center, randomized, prospective, parallel clinical trial of efficacy and safety of IN ketamine compared to IV and IM morphine for analgesia in the emergency department (ED). A convenience sample of 90 patients aged 18-70 experiencing moderate-severe acute traumatic pain (≥80 mm on 100 mm Visual Analog Scale [VAS]) were randomized to receive either 1.0 mg/kg IN ketamine, 0.1 mg/kg IV MO or 0.15 mg/kg IM MO. Pain relief and adverse effects were recorded for 1 h post-administration. The primary outcome was efficacy of IN ketamine compared to IV and IM MO, measured by "time-to-onset" (defined as a ≥15 mm pain decrease on VAS), as well as time to and degree of maximal pain reduction.

RESULTS

The 3 study groups showed a highly significant, similar maximal pain reduction of 56 ± 26 mm for IN Ketamine, and 59 ± 22 and 48 ± 30 for IV MO and IM MO, respectively. IN Ketamine provided clinically-comparable results to those of IV MO with regards to time to onset (14.3 ± 11.2 v. 8.9 ± 5.6 min, respectively) as well as in time to maximal pain reduction (40.4 ± 16.3) versus (33.4 ± 18), respectively.

CONCLUSIONS

IN ketamine shows efficacy and safety comparable to IV and IM MO. Given the benefits of this mode of analgesia in emergencies, it should be further studied for potential clinical applications.

TRIAL REGISTRATION

Retrospectively registered on 27 June 2016. ClinicalTrials.gov ID: NCT02817477.

Optimal Volume of Administration of Intranasal Midazolam in Children: A Randomized Clinical Trial

STUDY OBJECTIVE

The optimal intranasal volume of administration for achieving timely and effective sedation in children is unclear. We aimed to compare clinical outcomes relevant to procedural sedation associated with using escalating volumes of administration to administer intranasal midazolam.

METHODS

We conducted a randomized, single-blinded, 3-arm, superiority clinical trial. Children aged 1 to 7 years and undergoing laceration repair requiring 0.5 mg/kg intranasal midazolam (5 mg/mL) were block-randomized to receive midazolam using 1 of 3 volumes of administration: 0.2, 0.5, or 1 mL. Procedures were videotaped, with outcome assessors blinded to volume of administration. Primary outcome was time to onset of minimal sedation (ie, score of 1 on the University of Michigan Sedation Scale). Secondary outcomes included procedural distress, time to procedure start, deepest level of sedation achieved, adverse events, and clinician and caregiver satisfaction.

RESULTS

Ninety-nine children were enrolled; 96 were analyzed for the primary outcome and secondary outcomes, except for the outcome of procedural distress, for which only 90 were analyzed. Time to onset of minimal sedation for each escalating volume of administration was 4.7 minutes (95% confidence interval [CI] 3.8 to 5.4 minutes), 4.3 minutes (95% CI 3.9 to 4.9 minutes), and 5.2 minutes (95% CI 4.6 to 7.0 minutes), respectively. There were no differences in secondary outcomes except for clinician satisfaction with ease of administration: fewer clinicians were satisfied when using a volume of administration of 0.2 mL.

CONCLUSION

There was a slightly shorter time to onset of minimal sedation when a volume of administration of 0.5 mL was used compared with 1 mL, but all 3 volumes of administration produced comparable clinical outcomes. Fewer clinicians were satisfied with ease of administration with a volume of administration of 0.2 mL.

Effect of solubility enhancement on nasal absorption of meloxicam

Besides the opioids the standard management of the World Health Organization suggests NSAIDs (non-steroidal anti-inflammatory drugs) alone or in combination to enhance analgesia in malignant and non-malignant pain therapy. The applicability of NSAIDs in a nasal formulation is a new approach in pharmaceutical technology. In order to enhance the nasal absorption of meloxicam (MX) as an NSAID, its salt form, meloxicam potassium monohydrate (MXP), registered by Egis Plc., was investigated in comparison with MX. The physico-chemical properties of the drugs (structural analysis, solubility and dissolution rate) and the mucoadhesivity of nasal formulations were controlled. In vitro and in vivo studies were carried out to determine the nasal applicability of MXP as a drug candidate in pain therapy. It can be concluded that MX and MXP demonstrated the same equilibrium solubility at the pH5.60 of the nasal mucosa (0.017mg/ml); nonetheless, MXP indicated faster dissolution and a higher permeability through the synthetic membrane. The animal studies justified the short T_max value (15min) and the high AUC of MXP, which is important in acute pain therapy. It can be assumed that the low mucoadhesivity of MXP spray did not increase the residence time in the nasal cavity, and the elimination from the nasal mucosa was therefore faster than in the case of MX. Further experiments are necessary to prove the therapeutic relevance of this MXP-containing innovative intranasal formulation.

Development and gamma-scintigraphy study of Hibiscus rosasinensis polysaccharide-based microspheres for nasal drug delivery

OBJECTIVE

This work describes the application of natural plant polysaccharide as pharmaceutical mucoadhesive excipients in delivery systems to reduce the clearance rate through nasal cavity.

METHODS

Novel natural polysaccharide (Hibiscus rosasinensis)-based mucoadhesive microspheres were prepared by using emulsion crosslinking method for the delivery of rizatriptan benzoate (RB) through nasal route. Mucoadhesive microspheres were characterized for different parameters and nasal clearance of technetium-99m ((99m)Tc)-radiolabeled microspheres was determined by using gamma-scintigraphy.

RESULTS

Their Fourier transform infrared spectroscopy (FTIR) and X-ray diffraction (XRD) studies showed that the drug was stable during preparation of microspheres. Aerodynamic diameter of microspheres was in the range 13.23 ± 1.83-33.57 ± 3.69 µm. Change in drug and polysaccharide ratio influenced the mucoadhesion, encapsulation efficiency and in-vitro release property. Scintigraphs taken at regular interval indicate that control solution was cleared rapidly from nasal cavity, whereas microspheres showed slower clearance (p < 0.005) with half-life of 160 min.

CONCLUSION

Natural polysaccharide-based microspheres achieved extended residence by minimizing effect of mucociliary clearance with opportunity of sustained delivery for longer duration.

Brain Uptake of Neurotherapeutics after Intranasal versus Intraperitoneal Delivery in Mice

There is a growing global prevalence of neurodegenerative diseases such as Alzheimer's disease and dementia. Current treatment for neurodegenerative diseases is limited due to the blood brain barrier's ability to restrict the entry of therapeutics to the brain. In that context, direct delivery of drugs from nose to brain has gained emerging interest as an important alternative to oral and parenteral routes of administration. Although there are considerable reports showing promising results after intranasal drug delivery in various disease-models and investigatory human clinical trials, there are very few studies showing a detailed pharmacokinetics with regard to the uptake and retention of intranasally delivered material(s) within specific brain regions, which are critical determining factors for dosing conditions and optimal treatment regimen. This investigation compared a time-dependent brain uptake and resident time of various radiolabeled candidate neurotherapeutics after a single bolus intranasal or intraperitoneal administration in mice. Results indicate that the brain uptake of intranasally delivered therapeutic(s) is > 5 times greater than that after intraperitoneal delivery. The peak uptake and resident time of all intranasally delivered test therapeutics for all brain regions is observed to be between 30min-12h, depending upon the distance of brain region from the site of administration, followed by gradual fading of radioactive counts by 24h post intranasal administration. Current study confirms the usefulness of intranasal administration as a non- invasive and efficient means of delivering therapeutics to the brain to treat neurodegenerative diseases including Alzheimer's disease.

Quantitative analysis of drug delivery to the brain via nasal route

The blood-brain barrier (BBB) prevents drugs' permeability into the brain and limits the management of brain diseases. Intranasal delivery is a convenient route of drug administration that can bypass the BBB and lead to a direct delivery of the drug to the brain. Indeed, drug accumulation in the brain following intranasal application of a drug solution, or of a drug encapsulated in specialized delivery systems (DDSs), has been reported in numerous scientific publications. We aimed to analyze the available quantitative data on drug delivery to the brain via the nasal route and to reveal the efficiency of brain drug delivery and targeting by different types of nasally-administered DDSs. We searched for scientific publications published in 1970-2014 that reported delivery of drugs or model compounds to the brain via intranasal and parenteral routes, and contained quantitative data that were sufficient for calculation of brain targeting efficiency. We identified 73 publications (that reported data on 82 compounds) that matched the search criteria and analyzed their experimental settings, formulation types, analytical methods, and the claimed efficiencies of drug brain targeting: drug targeting efficiency (%DTE) and nose-to-brain direct transport (%DTP). Outcomes of this analysis indicate that efficiency of brain delivery by the nasal route differs widely between the studies, and does not correlate with the drug's physicochemical properties. Particle- and gel-based DDSs offer limited advantage for brain drug delivery in comparison to the intranasal administration of drug solution. Nevertheless, incorporation of specialized reagents (e.g., absorption enhancers, mucoadhesive compounds, targeting residues) can increase the efficiency of drug delivery to the brain via the nasal route. More elaborate and detailed methodological and analytical characterizations and standardized reporting of the experimental outcomes are required for reliable quantification of drug targeting to the brain by the nasal route. Quantitative analysis of these data will facilitate the development of DDSs with high brain targeting efficiency.

Natural mucoadhesive microspheres of Abelmoschus esculentus polysaccharide as a new carrier for nasal drug delivery

This work describes the preparation and evaluation of mucoadhesive microspheres, using Abelmoschus esculentus polysaccharide as a novel carrier for safe and effective delivery of rizatriptan benzoate into nasal cavity. The polysaccharide was extracted from the fruit of A. esculentus and mucoadhesive microspheres were prepared by emulsification, followed by crosslinking using epichlorohydrin. Prepared microspheres were evaluated for size, morphology, swelling properties, mucoadhesive strength, encapsulation efficiency and drug release. Microspheres were found to release 50% of drug within 15 min and rest of the drug was released within 60 min. The drug release was found to decrease with increasing concentration of polysaccharide. To determine the retention time of the microspheres in the nasal cavity of rabbits, the microspheres were radiolabelled with (99m)Tc and subjected to gamma scintigraphy. The results showed a significant improvement in the nasal retention of the microspheres as compared to the aqueous solution of radiolabelled free-drug.

A response to the opioid overdose epidemic: naloxone nasal spray

Opioid overdose morbidity and mortality is recognized to have epidemic proportions. Medical and public health agencies are adopting opioid harm reduction strategies to reduce the morbidity and mortality associated with overdose. One strategy developed by emergency medical services and public health agencies is to deliver the opioid antidote naloxone injection intranasally to reverse the effects of opioids. Paramedics have used this route to quickly administer naloxone in a needle-free system and avoiding needle-stick injuries and contracting a blood-born pathogen disease such as hepatitis or human immunodeficiency virus. Public health officials advocate broader lay person access since civilians are likely witnesses or first responders to an opioid overdose in a time-acute setting. The barrier to greater use of naloxone is that a suitable and optimized needlefree drug delivery system is unavailable. The scientific basis for design and study of an intranasal naloxone product is described. Lessons from nasal delivery of opioid analgesics are applied to the consideration of naloxone nasal spray.

Fentanyl pectin nasal spray: in breakthrough pain in opioid-tolerant adults with cancer

Fentanyl pectin nasal spray (PecFent®) uses a novel pectin-based delivery system that turns from an aqueous solution into a gel when applied to mucosal surfaces. Fentanyl is absorbed in a controlled manner from the pectin gel formed in the nasal cavity, and has a rapid onset of pain relief and duration of action that matches the time course of a typical episode of breakthrough pain in cancer (BTPc). Relative to administration as oral transmucosal fentanyl, fentanyl administered as fentanyl pectin nasal spray is more rapidly absorbed, reaches higher maximum plasma concentrations and has greater bioavailability. In the treatment of BTPc in two randomized, double-blind, crossover trials in opioid-tolerant adults, fentanyl pectin nasal spray (100-800 μg titrated doses) was significantly more effective than placebo in reducing pain intensity and provided a significantly faster onset of pain relief than oral immediate-release morphine. During long-term treatment of BTPc episodes, fentanyl pectin nasal spray consistently provided effective pain relief in an open-label, 16-week trial. Most patients were satisfied or very satisfied with the ease of use and convenience of the nasal spray. Fentanyl pectin nasal spray 100-800 μg was generally well tolerated and was not associated with nasal tolerability problems.

Intranasal fentanyl for pain control: current status with a focus on patient considerations

Of several newer delivery systems under development and investigation for the administration of opioids, the intranasal route has received a substantial amount of attention. Intranasal administration is a convenient form of delivery that is applicable to several opioids. It has the potential for self-administration, combined with a rapid onset of action, allowing for patient-controlled analgesia. In clinical practice, intranasal administration has been found to be a reliable drug delivery method that is familiar to patients. Intranasal opioids have proven to be useful in both in-hospital and out-of-hospital pain management settings. Fentanyl, a highly lipophilic step 3 opioid, has been evaluated for intranasal administration. The purpose of this review is to examine the role of the nasal route of opioid administration and examine the evidence base for the use of fentanyl intranasally.

Drug delivery to the CNS and polymeric nanoparticulate carriers

The delivery of drugs to the CNS is hampered by the existence of the blood–brain barrier (BBB). Nowadays, medicinal chemists follow defined rules for the development of drugs able to cross the BBB. At the same time, the parameters needed in order to gain valuable estimates of brain drug delivery are well defined. Despite the limits in molecular weight that allow drugs to cross the BBB, it was shown that nanotech products, in particular properly functionalized nanoparticles, spherical particles of approximately 200 nm in diameter, are able to cross the BBB after intravenous administration and act as drug carriers for CNS. Moreover, peptides as ligands for receptors present on the brain endothelium, or able to cross the BBB and to act as carriers for CNS drug delivery in the form of conjugates with drugs, have been discovered and started to be studied as targeting moieties for nanoparticulate systems. This article will discuss the results obtained so far in the field of nanoparticle drug carriers for CNS and highlight the parameters needed in order to fully characterize these hitherto largely unknown delivery systems. Even if promising results have been obtained, more studies are needed in order to fully evaluate the clinical potential of this drug-delivery system.