Comparison of a needle-free high-pressure injection system with needle-tipped injection of intracavernosal alprostadil for erectile dysfunction

Dynamic mechanical interaction between injection liquid and human tissue simulant induced by needle-free injection of a highly focused microjet

This study investigated the fluid-tissue interaction of needle-free injection by evaluating the dynamics of the cavity induced in body-tissue simulant and the resulting unsteady mechanical stress field. Temporal evolution of cavity shape, stress intensity field, and stress vector field during the injection of a conventional injection needle, a proposed highly focused microjet (tip diameter much smaller than capillary nozzle), and a typical non-focused microjet in gelatin were measured using a state-of-the-art high-speed polarization camera, at a frame rate up to 25,000 f.p.s. During the needle injection performed by an experienced nurse, high stress intensity lasted for an order of seconds (from beginning of needle penetration until end of withdrawal), which is much longer than the order of milliseconds during needle-free injections, causing more damage to the body tissue. The cavity induced by focused microjet resembled a funnel which had a narrow tip that penetrated deep into tissue simulant, exerting shear stress in low intensity which diffused through shear stress wave. Whereas the cavity induced by non-focused microjet rebounded elastically (quickly expanded into a sphere and shrank into a small cavity which remained), exerting compressive stress on tissue simulant in high stress intensity. By comparing the distribution of stress intensity, tip shape of the focused microjet contributed to a better performance than non-focused microjet with its ability to penetrate deep while only inducing stress at lower intensity. Dynamic mechanical interaction revealed in this research uncovered the importance of the jet shape for the development of minimally invasive medical devices.

A liquid breakdown driven non-invasive microjet injection system

The purpose of this study was to develop a microjet having fully skin-penetrable jet speed, moderately small volume, and highly repeatable injection, and eventually providing a device with medical efficacy for less tissue destruction and pain. The injector allows a small volume of drug stream (0.1-1.7 µL) to flow out at a frequency of ~16 Hz, and employs two different sources of energy, namely electrical and optical, which are converted into kinetic energy of the penetrating drug solution using liquid breakdown (dielectric or laser-induced). The medical efficacy of the microjet injection was evaluated through ex-vivo and in-vivo procedures in a mouse model. Both sources of liquid breakdown generate a skin-penetrable jet speed of 200-330 m/s. These fast and repetitive jets in a small volume pass through the epidermis to exert their efficacy. The driving pressure provided by dielectric breakdown showed an extensive increase per input energy increase, which is deemed appropriate for deep skin penetration. In contrast, the laser-induced breakdown exhibited a saturation in jet speed with increasing input energy, which is indicative of a low energy conversion efficiency. The results are promising for medical procedures that require uniform drug injection over a large area, and small dosage control during intradermal procedures.

Evaluation of the sensitivity of different doses of vasoactive drugs in diagnosing erectile dysfunction in impotent patients: a prospective case-control study

Introduction

Erectile dysfunction (ED) is one of the most common sexual disorders worldwide affecting about 30 million men in the United States, and an estimated 100 million men worldwide. Penile duplex doppler ultrasound (PDDU) is performed using an intracavernosal injection (ICI) of a vasoactive agent to demonstrate both arterial insufficiency and veno-occlusive dysfunction. This article aims to evaluate the sensitivity of different doses of different vasoactive agents used to diagnose ED in impotent patients.

Material and methods

This study recruited 90 subjects with ED and 100 healthy subjects as controls. All of the subjects were assessed using the International Index of Erectile Function score (IIEF-5) while degree of erection was assessed by the Erection Hardness Score (EHS). Two penile duplex tests were done for each candidate two weeks apart.

Results

None of the sample population achieved a normal clinical response (EHS >2) to 10 ug PGE1. In contrast, 60 controls (60%) had a normal response (EHS >2) to 10 ug PGE1. This difference in response between the sample and control populations to 10 ug PGE1 was of high statistical significance 11 (p <0.001). In contrast, 54 (60%) out of the 90 cases had normal clinical response (EHS >2) to 0.25cc Trimix (everywhere). Interestingly, 96 controls (96%) demonstrated normal response (EHS >2) to 0.25cc Trimix. This difference in response between the sample and control populations to 0.25 cc Trimix was also of high statistical significance (p <0.001).

Conclusions

Our study demonstrated a statistically significant association between the response to Trimix over PGE1 and peak systolic velocity (PSV) and end diastolic velocity (EDV). Thus, we conclude that 0.25 cc Trimix is more sensitive than 20 ug PGE1 in diagnosing ED for impotent patients and also provides a more potent response.

The Effectiveness of Jet (Needle-Free) Injector to Provide Anesthesia in Child Circumcision under Local Anesthesia

OBJECTIVE

In our study, we aimed to evaluate the effectiveness of a needle-free (jet) injector in local anesthesia for circumcision.

MATERIALS AND METHODS

A total of 64 children were divided into two groups as jet injector group (n = 32) and conventional needle group (n = 32). Ring block was applied 6-8 times with a jet injector that sprayed each time 0.1 ml (2 mg) of lidocaine in jet injector group. In conventional needle group, ring block was applied with 2 mg/kg lidocaine injection. Using FLACC (Face, Legs, Activity, Cry, Consolability) pain scale, pain score during local anesthetic injection, anesthesia start time and pain score during circumcision were determined for both groups.

RESULTS

The mean age of the patients was 3.99 ± 1.41 years in jet injector group and 3.88 ± 1.33 years in conventional needle group. The mean FLACC pain score during the anesthesia procedure was 4.75 ± 0.25 in jet injector group, while it was 7.06 ± 0.24 in conventional needle group. FLACC pain scores were found to be significantly lower in jet injector group (p = 0.0001). During circumcision, the mean FLACC scores were 4.91 ± 0.29 and 2.31 ± 0.18 for jet injector group and conventional needle group, respectively. These FLACC pain scores were found to be significantly lower in conventional needle group (p = 0.0001).

CONCLUSION

Our study showed that anesthesia using a jet injector can not provide sufficient analgesia so as to comfortably complete circumcision in pediatric circumcisions performed under local anesthesia.

Current trends in needle-free jet injection: an update

Background

Jet injection can be defined as a needle-free drug delivery method in which a high-speed stream of fluid impacts the skin and delivers a drug. Despite 75 years of existence, it never reached its full potential as a strategic tool to deliver medications through the skin.

Objective

The aim of this review was to evaluate and summarize the evolution of jet injection intradermal drug delivery method including technological advancements and new indications for use.

Methods

A review of the literature was performed with no limits placed on publication date.

Results

Needleless injectors not only reduce pain during drug delivery but also confine the drug more evenly in the dermis. Understanding skin properties of the injection site is a key factor to obtain optimal results as well as setting the right parameters of the jet injector. Until the advent of disposable jet injectors/cartridges, autoclaving of the injector remains the only reliable method to eliminate the risk of infection. Needle-free intradermal injection using corticosteroids and/or local anesthetics is well documented with promising indications being developed.

Limitations

Limitations of the review include low-quality evidence, small sample sizes, varying treatment parameters, and publication bias.

Conclusion

New developments may help reconsider the use of jet injection technology. Future studies should focus on measurable optimized parameters to insure a safe and effective outcome.

Needle-free delivery of macromolecules through the skin using controllable jet injectors

INTRODUCTION

Transdermal delivery of drugs has a number of advantages in comparison to other routes of administration. The mechanical properties of skin, however, impose a barrier to administration and so most compounds are administered using hypodermic needles and syringes. In order to overcome some of the issues associated with the use of needles, a variety of non-needle devices based on jet injection technology has been developed.

AREAS COVERED

Jet injection has been used primarily for vaccine administration but has also been used to deliver macromolecules such as hormones, monoclonal antibodies and nucleic acids. A critical component in the more recent success of jet injection technology has been the active control of pressure applied to the drug during the time course of injection.

EXPERT OPINION

Jet injection systems that are electronically controllable and reversible offer significant advantages over conventional injection systems. These devices can consistently create the high pressures and jet speeds necessary to penetrate tissue and then transition smoothly to a lower jet speed for delivery of the remainder of the desired dose. It seems likely that in the future this work will result in smart drug delivery systems incorporated into personal medical devices and medical robots for in-home disease management and healthcare.

Pathophysiological role of the renin-angiotensin system on erectile dysfunction

BACKGROUND

The renin-angiotensin system (RAS) has been shown to play an active role within the erectile tissues. The aim of this narrative review is to summarize the literature addressing the pathophysiological role of RAS on erectile function. Additionally, we update evidence on recent findings on the role of the Ang-(1-7) and Mas receptor on the erectile function and its therapeutic potential for treating erectile dysfunction (ED).

MATERIALS AND METHODS

This narrative review is based on the material searched and obtained via MEDLINE and PubMed up to November 2012. The search terms we used are 'angiotensin, erectile dysfunction, renin, Mas receptor' in combination with 'pathophysiology, fibrosis, pathways'.

RESULTS

The levels of angiotensin (Ang) II, the main component of this system, are increased in the corpus cavernosum as compared to those found in the systemic circulation. Moreover, emerging evidence indicates that an increased activity of Ang II via AT1 receptor might contribute to the development of ED, whereas the pharmacological blockage of Ang II/AT1 actions has beneficial effects on the erection. On the other hand, the heptapeptide Ang-(1-7), known as a major endogenous counter-regulator of Ang II actions, favours penile erection via the activation of Mas receptor.

CONCLUSIONS

Ang-(1-7) and Mas receptor pathway might be considered as a promising therapeutic target for the treatment of ED.

A systematic review of measures for reducing injection pain during adult immunization

OBJECTIVE

To evaluate the effectiveness of different pain-relieving interventions to reduce pain from immunization in adults.

DATA SOURCES

MEDLINE (1950 to October Week 3 2008) PsycINFO (1967 to December Week 1 2008), CINAHL (1982 to October Week 4 2008), EMBASE (1980 to 2008 Week 43) and the Cochrane Central Register of Controlled Trials (3rd Quarter 2008).

REVIEW METHODS

Databases were searched for trials of pharmacological, behavioural, physical or operator-dependant techniques to reduce pain from immunization in adults. The primary outcome was pain as assessed by visual analogue scale or other numeric rating scale.

RESULTS

Six studies representing 853 participants were identified. One study evaluating pharmacological interventions (lidocaine-prilocaine) found them to be effective in reducing pain from immunization. Similarly, two studies evaluating physical pain relieving techniques, either skin cooling interventions (Fluori-Methane) or tactile stimulation (manual pressure at the site of injection) found them to reduce pain. One study of jet injectors found them to be more painful than conventional needle and syringe. Neither freezing needles nor warming vaccines was found to be effective in reducing pain. No studies investigated psychological interventions or oral analgesics (acetaminophen and ibuprofen).

CONCLUSION

There was limited evidence to support the use of lidocaine-prilocaine, Fluori-Methane and manual pressure for reducing immunization pain in adults. There was limited evidence of more pain with jet injectors compared to needle and syringe. Due to limited data, we recommend further investigation of methods to reduce immunization pain in adults, primarily psychological and physical techniques.

Needle-free liquid jet injections: mechanisms and applications

Liquid jet injections employ a high-speed jet to puncture the skin and deliver drugs without the use of a needle. They have been used to deliver a number of macromolecules including vaccines and insulin, as well as small molecules, such as anesthetics and antibiotics. This article reviews liquid jet injectors with respect to their historical perspective, clinical applications, mechanisms and future prospects. An overview of the use of jet injectors for delivery of vaccines, insulin and growth hormones is presented. Particular attention is paid to the mechanistic understanding of jet injections, especially the dependence of jet penetration on parameters such as nozzle diameter, velocity and jet power. Finally, gaps in the current understanding are presented and suggestions for future research and development are made.

Current status and future prospects of needle-free liquid jet injectors

Needle-free liquid jet injectors have been used for more than 50 years for parenteral delivery of vaccines and drugs. Although excellent bioavailability has been reported for a number of drugs, occasional pain and bruising have limited wide acceptance of jet injectors. This article reviews jet injectors with respect to their current clinical applications, emerging applications, mechanistic understanding and future prospects.