Hydrogel-forming microneedle arrays exhibit antimicrobial properties: potential for enhanced patient safety

We describe, for the first time, the microbial characterisation of hydrogel-forming polymeric microneedle arrays and the potential for passage of microorganisms into skin following microneedle penetration. Uniquely, we also present insights into the storage stability of these hydroscopic formulations, from physical and microbiological viewpoints, and examine clinical performance and safety in human volunteers. Experiments employing excised porcine skin and radiolabelled microorganisms showed that microorganisms can penetrate skin beyond the stratum corneum following microneedle puncture. Indeed, the numbers of microorganisms crossing the stratum corneum following microneedle puncture were greater than 10⁵ cfu in each case. However, no microorganisms crossed the epidermal skin. When using a 21G hypodermic needle, more than 10⁴ microorganisms penetrated into the viable tissue and 10⁶ cfu of Candida albicans and Staphylococcus epidermidis completely crossed the epidermal skin in 24 h. The hydrogel-forming materials contained no microorganisms following de-moulding and exhibited no microbial growth during storage, while also maintaining their mechanical strength, apart from when stored at relative humidities of 86%. No microbial penetration through the swelling microneedles was detectable, while human volunteer studies confirmed that skin or systemic infection is highly unlikely when polymeric microneedles are used for transdermal drug delivery. Since no pharmacopoeial standards currently exist for microneedle-based products, the exact requirements for a proprietary product based on hydrogel-forming microneedles are at present unclear. However, we are currently working towards a comprehensive specification set for this microneedle system that may inform future developments in this regard.

Botulinum toxin type A injection without isopropyl alcohol antisepsis

PURPOSE

To evaluate the infection rate after botulinum toxin type A injection without the use of isopropyl alcohol antisepsis. Isopropyl alcohol 70% solution has been used for routine skin preparation prior to botulinum toxin injection for decades; however, alcohol antisepsis does not routinely sterilize the skin, and it may not reduce the injection site infection rate.

METHODS

The authors performed a retrospective analysis of patients undergoing botulinum toxin type A injection without the use of isopropyl alcohol antisepsis from one surgeon from October 1999 through December 2004. Charts were reviewed for patient age, gender, indication, total number of visits, total number of needles, total number of injections, and complications attributable to infection.

RESULTS

One hundred forty-two patients underwent botulinum toxin type A injection without isopropyl alcohol antisepsis during the study period. Patients underwent a total of 11,627 injections during the study period. Average number of visits was 6 (range, 1-25 visits). Average follow-up was 707 days (range, 7-2,165 days). No patient receiving botulinum toxin type A injection without isopropyl alcohol antisepsis sustained a local complication consistent with infection.

CONCLUSIONS

Injection of botulinum toxin type A reconstituted with preserved saline results in an extremely low rate of infection.

Feasibility of an evidence-based literature search service for general practitioners

OBJECTIVE

To test the feasibility of an evidence-based clinical literature search service to help answer general practitioners' (GPs') clinical questions.

DESIGN

Two search services supplied GPs who submitted questions with the best available empirical evidence to answer these questions. The GPs provided feedback on the value of the service, and concordance of answers from the two search services was assessed.

SETTING

Two literature search services (Queensland and Victoria), operating for nine months from February 1999.

MAIN OUTCOME MEASURES

Use of the service; time taken to locate answers; availability of evidence; value of the service to GPs; and consistency of answers from the two services.

RESULTS

58 GPs asked 160 questions (29 asked one, 11 asked five or more). The questions concerned treatment (65%), aetiology (17%), prognosis (13%), and diagnosis (5%). Answering a question took a mean of 3 hours 32 minutes of personnel time (95% CI, 2.67-3.97); nine questions took longer than 10 hours each to answer, the longest taking 23 hours 30 minutes. Evidence of suitable quality to provide a sound answer was available for 126 (79%) questions. Feedback data for 84 (53%) questions, provided by 42 GPs, showed that they appreciated the service, and asking the questions changed clinical care. There were many minor differences between the answers from the two centres, and substantial differences in the evidence found for 4/14 questions. However, conclusions reached were largely similar, with no or only minor differences for all questions.

CONCLUSIONS

It is feasible to provide a literature search service, but further assessment is needed to establish its cost effectiveness.