Advanced formulation design: improving drug therapies for the management of severe and chronic pain

Injectable peptide hydrogels for controlled-release of opioids

Peptide-based hydrogels as a drug carrier system for the subcutaneous administration of morphine.

Injection of Pharmaceuticals Designed for Oral Use: Harms Experienced and Effective Harm Reduction Through Filtration

Several pharmaceutical products are liable to 'abuse' or use outside their prescription, which frequently involves their injection. Examples are slow-release forms of morphine and oxycodone, and sublingual buprenorphine. During injection preparation, the drug is extracted into water, after crushing and heating the tablet if considered necessary. Since these products are designed for oral administration, they can contain excipients (ingredients other than the drug) which are poorly soluble, resulting in suspension of particles in the injection solution. Injected particles are able to produce medical complications such as the blockage of small blood vessels leading to ischaemia (inadequate blood flow) and tissue damage. Filtration can be used to remove particles from the suspension; including bacteria if the porosity is small enough (0.2 μm). However, filters are liable to blockage when overloaded, especially if the pore size is small. This problem can be minimised by using a larger pore size (e.g. 5-10 μm), but the resulting filtrate will contain many residual small particles. The use of two filters, coarse and fine, either sequentially or in a double membrane device, enables removal of the majority of particles as well as bacteria, although not quite meeting pharmaceutical standards for safe injection. Although not yet evaluated by a clinical trial, this highly effective filtration process would be expected to greatly reduce the risk of vascular and related complications, as well as non-viral infections. Careful technique ensures that drug is not lost by filtration, a priority for most drug consumers. Practical issues that affect acceptability of filtration by injecting drug users, including ease of use and cost, will need to be considered. However, given the laboratory evidence demonstrating the effectiveness of filters it is time to consider these tools as essential for safe injection as sterile needles/syringes for the world's approximately 16 million people who inject drugs.

Assessment of extended-release opioid analgesics for the treatment of chronic pain

Approximately 3.8 million patients annually receive extended-release (ER) or long-acting opioid prescriptions in the outpatient setting, around half of which are written by primary care physicians. Compared with short-acting, immediate-release (IR) formulations, ER and oral long-acting opioid analgesics are associated with clinical advantages, such as extended periods of time during which drug plasma levels are within the therapeutic range, decreased peak-to-trough fluctuations, and prolonged analgesia over the dosing period. Additionally, ER opioids offer a more convenient, less frequent dosing regimen to chronic pain patients who are often taking several concomitant medications. The increased utilization of ER opioids has been accompanied by a rise in the misuse and abuse of these formulations. Certain pharmacokinetic parameters (e.g., longer time to maximum drug plasma concentration, lower maximum drug plasma concentration) may decrease the abuse potential of intact ER opioids by limiting the positive subjective and reinforcing effects relative to IR formulations. Putative abuse-deterrent formulations have also recently been introduced to impede physical manipulation of these formulations, or reduce the harm resulting from such behavior. Such formulations may represent an incremental advance to reduce non-oral forms of abuse. This article reviews the pharmacokinetic profiles and abuse-deterrent features of newer ER opioid analgesics for the treatment of moderate to severe chronic pain.

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

Background

Injections 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.

Methods

Injection 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.

Results

Unfiltered 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.

Conclusions

Apart 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.

A comparison of long- and short-acting opioids for the treatment of chronic noncancer pain: tailoring therapy to meet patient needs

Management of chronic noncancer pain (CNCP) requires a comprehensive assessment of the patient, the institution of a structured treatment regimen, an ongoing reassessment of the painful condition and its response to therapy, and a continual appraisal of the patient's adherence to treatment. For many patients with CNCP, the analgesic regimen will include opioids. Physicians should consider the available evidence of efficacy, the routes of administration, and the pharmacokinetics and pharmacodynamics of the various formulations as they relate to the temporal characteristics of the patient's pain. When making initial decisions, physicians should decide whether to prescribe a short-acting opioid (SAO) with a relatively quick onset of action and short duration of analgesic activity, a long-acting opioid (LAO) with a longer duration of analgesic action but a potentially longer onset of action, or both. Studies suggest that SAOs and LAOs are both effective for most types of CNCP. A review of published studies found no data to suggest that either SAOs or LAOs are generally more efficacious for treating any particular CNCP condition. The LAOs may provide more stable analgesia with less frequent dosing; however, opioid therapy should be tailored to the pain state and the individual patient, and SAOs may be appropriate for some patients with CNCP. MEDLINE and PubMed searches were conducted to locate relevant studies published from January 1975 to April 2008 using the following search terms: opioids, short-acting opioids, long-acting opioids, chronic pain, chronic pain AND opioids, and narcotics. English-only randomized controlled trials and nonrandomized studies were considered.