Analgesic effect of bisphosphonates in mice

Antiallodynic effect of etidronate, a bisphosphonate, in rats with adjuvant-induced arthritis: involvement of ATP-sensitive K+ channels

Bisphosphonates, pyrophosphate analogues, known as inhibitors of bone resorption, appear to cause analgesia in certain clinical painful situations. To detect clinically relevant analgesic property of etidronate, a non-aminobisphosphonate, we examined and characterized its antiallodynic effect in the rat with adjuvant-induced arthritis, in comparison with alendronate, an aminobisphosphonate, as determined by the von Frey test. Repeated systemic administration of etidronate at 10-40 mg/kg/day suppressed the adjuvant-induced mechanical allodynia in rat hindpaw, an effect reaching a plateau in approximately 10 days. Systemic or intraplantar (i.pl.) administration of ATP-sensitive K+ (K+ ATP) channel inhibitors, glibenclamide and/or tolbutamide, completely reversed the antiallodynic effect of etidronate within 1h in the arthritic rats, without affecting the nociceptive scores in naïve or arthritic animals that had not received etidronate. Alendronate, administered repeatedly, also revealed similar glibenclamide-reversible antiallodynic effect. In contrast, the antiallodynic effect of repeated systemic indomethacin was resistant to i.pl. glibenclamide in the arthritic rats. Repeated administration of etidronate or alendronate only slightly attenuated the adjuvant-evoked hindpaw edema. Among K+ ATP channel subunits, mRNAs for Kir6.1, SUR1, SUR2A and SUR2B were abundant in rat dorsal root ganglia, while Kir6.2 mRNA was poor. Our data demonstrate that repeated etidronate as well as alendronate exhibits antiallodynic activity in arthritic rats, which might be clinically relevant, and suggest involvement of K+ ATP channels in the underlying mechanisms.

Neuropathy-induced osteopenia in rats is not due to a reduction in weight born on the affected limb

Changes in bone mineral density (BMD) are associated with clinical neuropathies. Following nerve injury in the rat, there is a loss of BMD, which may be related to nerve injury or reduced mechanical loading. The purpose of this study was to investigate if altered mechanical loading is solely responsible for the observed loss of BMD in neuropathic pain models. In addition, we sought to study the action of chronic bisphosphonate treatment on both neuropathy-induced osteopenia and pain. We therefore had two hypotheses: firstly, that nerve injuries can have variable effects on hind limb bone loss in rats which are not attributable to differences in the extent of hind limb disuse and, secondly, that bisphosphonate treatment can reverse bone loss in a rat mononeuropathy model, and this is not attributable to bisphosphonate effects on nociception or hind paw unweighting. Male Sprague-Dawley rats were subject to chronic constriction injury (CCI), partial sciatic nerve ligation (PSN) or L5 + L6 spinal nerve ligation (SNL). Loss of BMD, defined as a numerically lower BMD as compared to control animals, was extreme following CCI (maximum ipsilateral/contralateral difference of 0.023 +/- 0.011); BMD loss following either PSN or SNL in the rat was subtle (0.010 +/- 0.002 and 0.013 +/- 0.012 g/cm2, respectively), significant only at early time points and had resolved by 7 weeks post-surgery. Chronic bisphosphonate treatment significantly inhibited CCI-induced osteopenia in the rat without inhibiting the reduction in weight-bearing tactile allodynia or mechanical hyperalgesia. Loss of BMD is observed in rats in a variety of neuropathic pain models. Lack of correlation between neuropathy-induced bone loss and weight bearing demonstrates that the bone loss is not simply a function of reduced mechanical loading and suggests that altered bone-nerve signaling is involved. Furthermore, chronic bisphosphonate treatment inhibits neuropathy-induced osteopenia without affecting behavioral measurements of neuropathic pain. This indicates that osteopenia is not directly related to neuropathic pain behaviors.

Intravenous pamidronate for pain relief in recent osteoporotic vertebral compression fracture: a randomized double-blind controlled study

INTRODUCTION

We performed a randomized, double-blind, controlled clinical trial comparing intravenous pamidronate and placebo for pain relief in recent osteoporotic vertebral compression fractures (VCF).

METHODS

Patients suffered from recent (<21 days), painful, osteoporosis-related VCF. They were randomized to receive daily intravenous infusions of either placebo or 30 mg pamidronate for three consecutive days (total pamidronate: 90 mg). The main criterion for efficacy was improvement in standing pain on a 100-mm visual analogical scale (VAS) at day 7. Secondary criteria were standing pain at days 3 and 30; supine pain at days 3, 7, and 30; patients' overall assessment of improvement; mobility index; and number of "20% responders" and "50% responders" (respectively, 20% and 50% improvement in standing pain at days 7 and 30). Statistical analysis with non-parametric tests was carried out on an intention to treat basis.

RESULTS

Thirty-two patients were enrolled in the study; 16 were given placebo and 16 pamidronate. Thirty-one patients were evaluated at day 7 and 26 patients at day 30. VAS pain decreased significantly in both groups at day 7 (placebo -23 mm, pamidronate -42 mm, p<0.01). The difference in pain scores between groups was -23.25 mm (confidence interval (CI) [-42.3; -4.2], p=0.018) at day 7 and -26 mm at day 30 (p=0.03), in favor of pamidronate. At day 7, there were 4 versus 12 "50% responders," respectively, in the placebo and in the pamidronate groups (likelihood ratio: 8.372; p=0.004) and 9 versus 14 "20% responders" (likelihood ratio: 4.038; p=0.044). At day 30, there were 5 versus 10 "50% responders," respectively, in the placebo and in the pamidronate groups, and 7 versus 11 "20% responders." Patients' overall assessment of improvement at day 7 was 37+/-26 mm in the placebo group and 59+/-30 mm in the pamidronate group (p=0.019), and 42+/-26 mm and 72+/-21 mm at day 30 (p=0.07). The two groups did not differ significantly at days 7 and 30 for supine pain, Schober index, or finger-ground distance. No significant adverse reaction related to treatment occurred.

CONCLUSION

Pamidronate provides rapid and sustained pain relief in patients with acute painful osteoporotic VCF and is well tolerated. Further investigations are needed to better define the place of pamidronate in the management of painful recent osteoporotic collapse.

Long-term analgesic effect of clodronate in rodents

Several studies have shown that treatment with bisphosphonates can reduce the pain associated with different painful diseases. In a previous study we demonstrated that in mice two bisphosponates, clodronate and pamidronate, had an antinociceptive effect under acute conditions not related to bone processes, after in vein (iv) or intracerebroventricular (icv) injection. The present study tested the time-dependent antinociceptive action of clodronate and pamidronate in comparison with that of acetylsalicylic acid (ASA) and morphine after iv and icv injection using the tail-flick test in acute and chronic treatment. The effects of clodronate on other measures of animal behaviour were also evaluated. In the tail-flick test, administration of clodronate iv produced an antinociceptive effect that was greater than that of ASA and statistically significant up to 16 h; pamidronate iv showed a significant antinociceptive effect for only 6 h. Clodronate and pamidronate icv showed an increase in tail-flick latency time that was significant and lasted for 16 and 6 h, respectively, while morphine produced an antinociceptive effect for 24 h. In the test we found significant differences between male and female mice in the latency time values but not in the length of the analgesic effect. In the chronic treatment paradigm, clodronate produced a significant increase of the tail-flick latency after the first injection. The analgesic effect increased up to 50% after 5 days of treatment. Significant analgesic effects were still present after 3, 7, and 14 days from the end of treatment. Clodronate did not produce any significant behavioural effects in the Rota-rod test, pentobarbital-induced sleeping time, and locomotor activity cage. These data indicate that clodronate presents a central and peripheral prolonged antinociceptive effect, without any behavioural side effects.

Treatment of chronic mechanical spinal pain with intravenous pamidronate: a review of medical records

We explored the effect of intravenous infusions of a bisphosphonate, pamidronate, in the management of chronic mechanical spinal pain, a worldwide public health problem in terms of lost workdays, medical treatment costs, and suffering. Bisphosphonates have an anti-nociceptive effect in animals. In humans, intravenous pamidronate relieves numerous painful conditions, including metastatic bone pain, ankylosing spondylitis, rheumatoid arthritis, and complex regional pain syndrome. We reviewed the charts of 25 patients who had experienced disabling spinal pain for several years, and whom we treated with intravenous pamidronate. None had a history of osteoporotic vertebral fractures or metastatic disease. Pain rating scores decreased in 91% of patients: on a 0-10 numeric rating scale, the mean pain change was -3.6 points and mean percentage change was -41% (P<0.0001). There was no increase in opioid or nonopioid analgesic medications associated with pain relief. The apparent analgesic effect of pamidronate for chronic mechanical spinal pain needs to be confirmed with placebo-controlled trials.

Disease modifying and anti-nociceptive effects of the bisphosphonate, zoledronic acid in a model of bone cancer pain

Inoculation of syngeneic MRMT-1 mammary tumour cells into one tibia of female rats produced tumour growth within the bone associated with a reduction in bone mineral density (BMD) and bone mineral content (BMC), severe radiological signs of bone destruction, together with the development of behavioural mechanical allodynia and hyperalgesia. Histological and radiological examination showed that chronic treatment with the bisphosphonate, zoledronic acid (30 microg/kg, s.c.), for 19 days significantly inhibited tumour proliferation and preserved the cortical and trabecular bone structure. In addition, BMD and BMC were preserved and a dramatic reduction of tartrate resistant acid phosphatase-positive polykaryocytes (osteoclasts) was observed. In behavioural tests, chronic treatment with zoledronic acid but not the significantly less effective bisphosphonate, pamidronate, or the selective COX-2 inhibitor, celebrex, attenuated mechanical allodynia and hyperalgesia in the affected hind paw. Zoledronic acid also attenuated mechanical hyperalgesia associated with chronic peripheral neuropathy and inflammation in the rat. In contrast, pamidronate or clodronate did not have any anti-hyperalgesic effect on mechanical hyperalgesia in the neuropathic and inflammatory pain models. We conclude that zoledronic acid, in addition to, or independent from, its anti-metastatic and bone preserving therapeutic effects, is an anti-nociceptive agent in a rat model of metastatic cancer pain. This unique property of zoledronic acid amongst the bisphosphonate class of compounds could make this drug a preferred choice for the treatment of painful bone metastases in the clinic.