Effect of filtration on morphine and particle content of injections prepared from slow-release oral morphine tablets

Abstract

BackgroundInjections of mixtures prepared from crushed tablets contain insoluble particles which can cause embolisms and other complications. Although many particles can be removed by filtration, many injecting drug users do not filter due to availability, cost or performance of filters, and also due to concerns that some of the dose will be lost.MethodsInjection solutions were prepared from slow-release morphine tablets (MS Contin®) replicating methods used by injecting drug users. Contaminating particles were counted by microscopy and morphine content analysed by liquid chromatography before and after filtration.ResultsUnfiltered tablet extracts contained tens of millions of particles with a range in sizes from < 5 μm to > 400 μm. Cigarette filters removed most of the larger particles (> 50 μm) but the smaller particles remained. Commercial syringe filters (0.45 and 0.22 μm) produced a dramatic reduction in particles but tended to block unless used after a cigarette filter. Morphine was retained by all filters but could be recovered by following the filtration with one or two 1 ml washes. The combined use of a cigarette filter then 0.22 μm filter, with rinses, enabled recovery of 90% of the extracted morphine in a solution which was essentially free of tablet-derived particles.ConclusionsApart from overdose and addiction itself, the harmful consequences of injecting morphine tablets come from the insoluble particles from the tablets and microbial contamination. These harmful components can be substantially reduced by passing the injection through a sterilizing (0.22 μm) filter. To prevent the filter from blocking, a preliminary coarse filter (such as a cigarette filter) should be used first. The filters retain some of the dose, but this can be recovered by following filtration with one or two rinses with 1 ml water. Although filtration can reduce the non-pharmacological harmful consequences of injecting tablets, this remains an unsafe practice due to skin and environmental contamination by particles and microorganisms, and the risks of blood-borne infections from sharing injecting equipment.

The filter of choice: filtration method preference among injecting drug users

“…Several studies [13,14] have evaluated the efficacy of IDUSF or wheel filters. Scott's research [13] also included some questions on filter preference.…”

Theory versus practice, bacteriological efficiency versus personal habits: A bacteriological and user acceptability evaluation of filtering tools for people who inject drugs

“…The bacteriological study in the present work highlighted the value of using filters with a porosity of less than 0.5 μm, as they limit the risk of bacterial and fungal infection to the largest extent possible. Although our study did not focus on particle analysis, we can comfortably affirm that particles are filtered more effectively by the lower porosity 0.22 and 0.45‐μm wheel filters than by Sterifilt .…”

“…The efficiency of the wheel filter in terms of particle filtration has been repeatedly shown in the literature for different wheel filter diameters as follows: 0.5 μm [28], 0.2 μm [1], 0.22 μm [24] and 0.22 and 0.45 μm [23]. With regard to bacteria filtration, a recent study showed that 0.22-μm wheel filters were effective in eliminating the strains tested (S. aureus, Streptococcus pyogenes and P. aeruginosa).…”

Uptake of wheel‐filtration among clients of a supervised injecting facility: Can structured education work?

“…The objectives of the structured education were to: (i) provide instruction on wheel‐filtration based on recommended practice and current evidence ; (ii) increase knowledge of the advantages of wheel‐filtration; and (iii) promote uptake of the practice. The key steps of the structured education were: MSIC Health Education Officers (HEO) received refresher training in the method to ensure consistent delivery. Participants agreed to: (i) provide their own opioid tablet; (ii) follow instruction from the HEO; and, (iii) accept responsibility for any actual or perceived drug loss. The education session took place during normal operating hours in the injecting room (a room with eight open booths that can seat two people). The HEO explained what equipment was required (Table ) and collected it with the participant. The HEO sat beside the participant in the booth.…”

“…The objectives of the structured education were to: (i) provide instruction on wheel-filtration based on recommended practice [11] and current evidence [5]; (ii) increase knowledge of the advantages of wheelfiltration; and (iii) promote uptake of the practice. The key steps of the structured education were:…”