Mark T. Roszkowski

Effect of NSAID administration on tissue levels of immunoreactive prostaglandin E2, leukotriene B4, and (S)-flurbiprofen following extraction of impacted third molars

&NA; Post‐operative pain and inflammation are frequently managed with non‐steroidal anti‐inflammatory drugs (NSAIDs). Despite the prevalence of their use, however, relatively little is known about in vivo tissue concentrations of inflammatory mediators at the site of tissue injury and their modulation by NSAIDs. This study compares the effect of oral administration of the NSAID flurbiprofen, to placebo, on tissue levels of immunoreactive prostaglandin E2 (iPGE2), leukotriene B4 (iLTB4), and (S)‐flurbiprofen within the surgical wound using implanted microdialysis probes in the dental impaction pain model. Twenty‐four healthy patients in need of extraction of partial to complete bony mandibular third molars were recruited for this randomized, double‐blind, placebo‐controlled study. Following pre‐operative administration of N2O/O2, midazolam i.v., and regional block anesthesia with 3% mepivacaine, each patient underwent surgical removal of their impacted third molars. Immediately following completion of the surgery, two semi‐permeable microdialysis probes (3 kDa molecular weight cut‐off) were implanted into each mandibular surgical site. Patients were taken to a recovery room and microdialysis samples and patient pain reports (visual analog scale, VAS) were collected at 30 min intervals for 4 h. Patients randomly received either flurbiprofen (200 mg orally) or placebo at the onset of post‐operative pain. Dialysate samples were collected, frozen, and later assayed for iPGE2, iLTB4, and (S)‐flurbiprofen levels. Results of this study show that flurbiprofen decreased post‐operative pain by approximately 70% compared to placebo‐treated patients (P<0.001). During the 4 h post‐operative timecourse of this study, flurbiprofen treatment significantly reduced peak tissue levels of iPGE2 (9.2±2.6 vs. 0.4±0.15 nM; P<0.001), without having a significant effect on peak tissue levels of iLTB4 (2.5±1.4 vs. 1.49±0.86 nM) compared to placebo treatment. Levels of (S)‐flurbiprofen significantly increased within the surgical wound exceeding therapeutic levels by 60 min after administration. Flurbiprofen is able to significantly suppress the local production of iPGE2 and provide significant analgesic efficacy without altering iLTB4 tissue levels in this model of acute post‐operative inflammatory pain. These data indicate that NSAIDs selectively alter eicosanoid levels within surgical wound and evoke analgesia at time points coincident with elevated wound levels of the drug. The combined use of microdialysis probes in awake patients who provide simultaneous pain reports may offer insight into peripheral mechanisms of inflammatory mediator release and pain.

Pharmacology of peripheral neuropeptide and inflammatory mediator release

Research conducted in the last 10 years has increased our knowledge on pain mechanisms substantially. Although many local tissue mediators, including neuropeptides, are known to exert pro-inflammatory effects, comparatively little is known about the actual tissue levels of these inflammatory mediators and their pharmacologic regulation. This article describes two new methods, clinical microdialysis and superfusion of dental pulp, which provide data on the pharmacology of peripheral neuropeptide and inflammatory mediator release. Collectively, these methods provide a biochemically based approach toward determining the mechanisms and management of orofacial pain.

Effect of intra-articular versus systemic anti-inflammatory drugs in a rabbit model of temporomandibular joint inflammation

PURPOSE In an attempt to better understand the time course of inflammatory mediator production or release in inflammatory joint disease, a rabbit model of acute temporomandibular joint (TMJ) inflammation was established. This model was used to evaluate the effects of specific anti-inflammatory agents administered either systemically (intraperitoneal, IP) or locally (intra-articular, IA) on the modulation of in vivo tissue levels of two prototypic inflammatory mediators, prostaglandin E2 (PGE2) and bradykinin (BK). MATERIALS AND METHODS An experimental model of inflammation was created by administering carrageenan (carra) into one joint and an equivalent volume of saline (control) into the contralateral joint of 42 male New Zealand White rabbits. The development of hyperthermia was assessed by placement of a microthermister probe into the joint space. The inflammatory mediators, immunoreactive PGE2 (iPGE2) and BK (iBK), were recovered with microdialysis probes, and samples were assayed in conjunction with specific pharmacologic interventions. In the first part of the study, the time course for the release or production of iBK and iPGE2 was determined. In the second part, the effects of IP versus IA administration of dexamethasone and a nonsteroidal anti-inflammatory drug, ketorolac tromethamine, were compared. Dexamethasone and ketorolac were administered at 3 hours and 1 hour, respectively, before the peak release of the inflammatory mediators. RESULTS The onset of IA hyperthermia, an index of inflammation, was evident by 90 minutes post-carra and reached a maximum of 1.2 degrees C above core temperature by 150 minutes post-carra. Intra-articular levels of iPGE2 and iBK peaked at 240 minutes (3.35+/-1.9 nmol/L) and 270 minutes (0.45+/-0.29 nmol/L), respectively, after the induction of inflammation in the superior joint space. iBK levels within the superior joint space were significantly decreased by dexamethasone and ketorolac. Ketorolac (50 microg) decreased iBK and iPGE2 levels when given IA or IP. With dexamethasone (3 mg), the levels of iBK were significantly reduced, and iPGE2 levels were not changed. CONCLUSIONS This study shows that the rabbit model of TMJ inflammation, with concurrent collection of iBK and iPGE2 via microdialysis, is a reproducible and reliable method to investigate the time course of inflammatory mediator release and their modulation by either the local or systemic administration of anti-inflammatory medications.

Tissue response to hydroxylapatite in induced diabetic and nondiabetic rats: Histologic evaluation

This study evaluated the tissue response to the subcutaneous implantation of nonporous hydroxylapatite (HA) in 24 induced-diabetic (ID) and 24 nondiabetic (ND) rats. One cubic centimeter of HA was implanted subcutaneously in each rats chest. Subgroups of 6 rats from the ID and ND groups were killed at 3, 6, 12, and 24 weeks postimplantation. The implants were removed with the surrounding soft tissues and processed for histologic evaluation. This revealed that soft tissue inflammation was mild at each time interval. There was a decreased response at 6 months in ND rats and a persistent inflammatory reaction in ID rats. Collagen maturity and fibroplasia increased within ND rats, whereas the ID rats showed a marked delay in collagen maturity and density. No osteogenesis was observed in any specimen. Dystrophic calcification was observed at the HA-tissue interface in 37% of ND and 59% of ID specimens. It was concluded that HA elicited a greater inflammatory response in ID than in ND rats when implated subcutaneously.

The Analgesic Interaction of Misoprostol with Nonsteroidal Anti-Inflammatory Drugs.

The purpose of this project was to evaluate the analgesic efficacy of misoprostol when combined with ibuprofen or diclofenac Na. Animal experiments using the inflamed rat paw formalin model suggested that misoprostol potentiates the analgesic effect of some NSAIDs (nonsteroidal anti-inflammatory drugs) including diclofenac Na but not propionic acid derivatives or opiates. The dental pain model was used to evaluate the clinical relevance of this interaction. Patients received a single oral dose of study medication following surgical removal of impacted teeth. Patients were medicated for moderate to severe postsurgical pain and then filled in an analgesic diary for a 6-h observation period. Several blood samples were taken over the observation period. In addition, microdialysis samples were taken directly from the extraction socket and were analyzed for immunoreactive prostaglandin E(2) levels. The studies were single-dose, parallel group and double-blind assays. In the first study, 70 patients received an oral dose of either placebo (n = 13), misoprostol 200 &mgr;g (n = 18), ibuprofen 200 mg (n = 19), or the combination of misoprostol + ibuprofen (n = 20). Misoprostol alone demonstrated a small analgesic effect compared to placebo. Both the ibuprofen and combination groups were substantially more effective than placebo but not different from each other. The combination group had higher ibuprofen blood levels during the first 45 min but had a lower C(max) and longer time to T(max). The second study evaluated oral doses of placebo (n = 11), misoprostol 200 &mgr;g (n = 21), diclofenac Na 50 mg (n = 18), and the combination of misoprostol + diclofenac Na (n = 20). Relative to placebo, misoprostol performance was similar to the first study. When the results of the two studies were combined, there was a small, but statistically significant, analgesic effect for misoprostol. Diclofenac Na was superior to both placebo and to misoprostol alone. The combination was the most effective treatment, and for hours 4--6 it was significantly better than diclofenac Na alone. Analysis of the blood samples showed an earlier and higher peak effect for the diclofenac Na group compared to the combination, and the combination again had a lower C(max). The microdialysis probe assays demonstrated that misoprostol depressed PGE(2) levels at the peripheral site of trauma over the first 2 h after surgery. These pilot studies used small samples, and the results only suggest trend effects. Both studies demonstrated that misoprostol 200 &mgr;g, a prostaglandin analog, does have an analgesic effect. When combined with ibuprofen, there was no potentiation of analgesia. In contrast, the combination of misoprostol + diclofenac Na demonstrated an enhanced peak effect, total effect for pain intensity difference and pain relief (sum pain intensity difference [SPID] and total pain relief [TOTPAR]), and

Extracranial and mandibular augmentation with hydroxyapatite-collagen in induced diabetic and nondiabetic rats☆

This study evaluated three hydroxyapatite (HA) preparations placed subperiosteally in rats given streptozotocin (70 mg/kg) to induce diabetes (ID) (n = 24) and in nondiabetic (ND) rats (n = 24) used as controls. Implants of 1) nonporous HA granules (HAG), 2) HA granules hand-mixed with bovine collagen (HACM), and 3) HA granules and purified fibrillar collagen in a preprocessed block (PFC-HA) were randomly placed in subperiosteal pockets created on the cranium and adjacent to the left/right mandibles of each rat. Six rats from each group were killed at 3, 6, 12, and 24 weeks postimplantation. Animals killed after 3 weeks showed sporadic bone proliferation and bone resorption, whereas those killed after 6, 12, and 24 weeks showed formation of new bone at the implant/bone interface. Contact of the implant with bone was a requirement for osteogenesis, but bone formed only into the basilar layers of the implants. The ID group showed the greatest inflammatory response as well as the greatest degree of osteogenesis at all intervals of time. The addition of collagen to HA appeared to reduce the inflammatory response. Specimens implanted with HACM showed the least inflammation of the three implanted materials in both ID and ND groups.

Subcutaneous implantation of hydroxylapatite/collagen in induced diabetic and non-diabetic rats

To evaluate tissue reaction to hydroxylapatite (HA) and HA/collagen mixtures in rats with uncontrolled induced diabetes, 48 males were divided: 24 with induced diabetes (ID) from Streptozotocin (70 mg/kg) and 24 non-diabetic (ND) controls. Three subcutaneous sites in each chest were randomly implanted with non-porous HA, or non-porous HA and bovine collagen, or non-porous HA and purified fibrillar collagen. Subgroups of 6 ID and 6 ND rats were killed at 4, 6, 12, and 24 weeks post-implantation. Histologic specimens showed that all materials elicited greater inflammatory response in ID than in ND at all intervals. Each specimen had HA particles encapsulated by host fibrous tissue. Compared to ND, ID specimens had markedly reduced ingrowth and maturity of collagen at each time interval. There was no osteogenesis, but there was dystrophic mineralization within the implant sites in both ID and ND. Mixed HA/collagen exceeded HA alone in maintaining implant contour. In soft tissue, no materials were osteoinductive. Adding collagen did not increase or decrease inflammatory reaction nor improve density and maturity of tissue synthesized around implants.