Neuroprotection of the Inner Retina Also Prevents Secondary Outer Retinal Pathology in a Mouse Model of Glaucoma

Purpose

We examined structural and functional changes in the outer retina of a mouse model of glaucoma. We examined whether these changes are a secondary consequence of damage in the inner retina and whether neuroprotection of the inner retina also prevents outer retinal changes.

Methods

We used an established microbead occlusion model of glaucoma whereby intraocular pressure (IOP) was elevated. Specific antibodies were used to label rod and cone bipolar cells (BCs), horizontal cells (HCs), and retinal ganglion cells (RGCs), as well as synaptic components in control and glaucomatous eyes, to assess structural damage and cell loss. ERG recordings were made to assess outer retina function.

Results

We found structural and functional damage of BCs, including significant cell loss and dendritic/axonal remodeling of HCs, following IOP elevation. The first significant loss of both BCs occurred at 4 to 5 weeks after microbead injection. However, early changes in the dendritic structure of RGCs were observed at 3 weeks, but significant changes in the rod BC axon terminal structure were not seen until 4 weeks. We found that protection of inner retinal neurons in glaucomatous eyes by pharmacological blockade of gap junctions or genetic ablation of connexin 36 largely prevented outer retinal damage.

Conclusions

Together, our results indicate that outer retinal impairments in glaucoma are a secondary sequalae of primary damage in the inner retina. The finding that neuroprotection of the inner retina can also prevent outer retinal damage has important implications with regard to the targets for effective neuroprotective therapy.

Effect of Pharmacological Inhibition of Fat-Mass and Obesity-Associated Protein on Nerve Trauma-Induced Pain Hypersensitivities

Genetic knockout or knockdown of fat-mass and obesity-associated protein (FTO), a demethylase that participates in RNA N6-methyladenosine modification in injured dorsal root ganglion (DRG), has been demonstrated to alleviate nerve trauma-induced nociceptive hypersensitivities. However, these genetic strategies are still impractical in clinical neuropathic pain management. The present study sought to examine the effect of intrathecal administration of two specific FTO inhibitors, meclofenamic acid (MA) and N-CDPCB, on the development and maintenance of nociceptive hypersensitivities caused by unilateral L5 spinal nerve ligation (SNL) in rats. Intrathecal injection of either MA or N-CDPCB diminished dose-dependently the SNL-induced mechanical allodynia, heat hyperalgesia, cold hyperalgesia, and spontaneous ongoing nociceptive responses in both development and maintenance periods, without altering acute/basal pain and locomotor function. Intrathecal MA also reduced the SNL-induced neuronal and astrocyte hyperactivities in the ipsilateral L5 dorsal horn. Mechanistically, intrathecal injection of these two inhibitors blocked the SNL-induced increase in the histone methyltransferase G9a expression and rescued the G9a-controlled downregulation of mu opioid receptor and Kv1.2 proteins in the ipsilateral L5 DRG. These findings further indicate the role of DRG FTO in neuropathic pain and suggest potential clinical application of the FTO inhibitors for management of this disorder.

Antiepileptic effect of gap-junction blockers in a rat model of refractory focal cortical epilepsy

PURPOSE

Epilepsy is the most common serious neurologic disease, and current treatments are ineffective for <or=30% of patients. Gap junctions have been implicated in seizure generation and propagation, and as such, may represent a novel therapeutic target but have been little investigated in vivo. We set out to assess the efficacy and tolerability of gap-junction blockers delivered to the seizure focus in a well-characterized model of refractory cortical epilepsy in rats.

METHODS

A chronic epilepsy focus was induced in the cortex of rats by using tetanus toxin, and subsequent studies were conducted in freely moving unanesthetized animals with frequent spontaneous seizures, as we previously described. Carbenoxolone, meclofenamic acid, and saline were applied directly to the seizure focus. EEG, electromyogram (EMG), and behavioral parameters were measured for >or=1 h before drug infusion and for >or=3 h afterward. No ill effects were observed.

RESULTS

An immediate and marked reduction in percentage of seizure time was seen in rats receiving carbenoxolone (baseline, 69.4%+/- 7.0% (SEM); maximum effect, 9.3%+/- 3.5%, p <or=0.001) and meclofenamic acid (baseline, 58.3%+/- 3.7%; maximum effect, 0.92%+/- 0.92%, p < 0.001). No effect was seen after saline infusion.

CONCLUSIONS

Gap-junction blockers applied focally are effective at suppressing seizures and, as such, represent a potential new treatment for epilepsy. Development of focal treatment strategies is essential in this regard.

Starch-based microspheres produced by emulsion crosslinking with a potential media dependent responsive behavior to be used as drug delivery carriers

This paper describes the development and characterization of starch microspheres for being used as drug delivery carriers in tissue engineering applications. The developed starch microspheres can be further loaded with specific growth factors and immobilized in scaffolds, or administrated separately with scaffolds. Furthermore and due to the processing conditions used, it is expected that these microspheres can be also used to encapsulate living cells. The aim of this study was to evaluate the efficacy of this methodology for further studies with biologically active agents or living cells. The starch microspheres were prepared using an emulsion crosslinking technique at room temperature to allow for the loading of biologically active agents. A preliminary study was performed to evaluate the incorporation of a model drug (nonsteroidal anti-inflammatory drug-NSAID) and investigate its release profile as function of changes in the medium parameters, such as ionic strength and pH. The developed starch-based drug delivery system has shown to be dependent on the ionic strength of the release medium. From preliminary results, the release seems to be pH-dependent due to the drug solubility. It was found that the developed microspheres and the respective processing route are appropriate for further studies. In fact, and based in the processing conditions and characterization, the developed system present a potential for the loading of different growth factors or even living cells on future studies with these systems for improving bone regeneration in tissue engineering, especially because the crosslinking reaction of the microspheres takes place at room temperature.

Role of nitric oxide and prostaglandins in the long-term control of renal function

Previous studies have reported evidence of an important interaction between nitric oxide (NO) and prostaglandins in the acute regulation of renal function. The objective of this study was to determine in conscious dogs whether the renal effects of the prolonged administration of a cyclooxygenase inhibitor are enhanced when NO synthesis is reduced. Meclofenamate infusion (5 microg x kg(-1) x min(-1)) during 4 consecutive days (n=8) elicited a continuous decrease (P<0.05) in renal blood flow and plasma renin activity and a transitory decrease in sodium excretion. NG-Nitro-L-arginine methyl ester (L-NAME) infusion (5 microg x kg(-1) x min(-1)) during 6 days (n=8) produced a significant increase in arterial pressure and a transitory decrease (P<0.05) in both renal blood flow and plasma renin activity. The simultaneous inhibition of NO and prostaglandin synthesis (n=7) led to an increase in arterial pressure and a decrease in renal blood flow similar to those observed during the administration of either L-NAME or meclofenamate. In contrast, this simultaneous inhibition produced a decrease in glomerular filtration rate, which was not observed in the previous groups, and also induced an increase in renal vascular resistance and a decrease in sodium excretion greater (P<0.05) than those found during the inhibition of either NO or prostaglandins. Only a transitory decrease in plasma renin activity was found during meclofenamate infusion in this group. The results of this study present new evidence that the renal vasoconstrictor and antinatriuretic effects induced by the prolonged infusion of a cyclooxygenase inhibitor are significantly enhanced when NO synthesis is reduced. These results suggest that renal function may be more sensitive to the prolonged administration of a cyclooxygenase inhibitor in situations where NO production is reduced.

In vivo and in vitro action of endothelin-1 on goat cerebrovascular bed

This study concerned the effects and mechanisms of action of endothelin-1 on the cerebral circulation. Cerebral blood flow was electromagnetically measured in awake goats. Endothelin-1 (0.01-0.3 nmol) produced dose-dependent decreases in this flow (maximal reduction = 34%) and increases in cerebrovascular resistance (maximal increase = 74%) (P < 0.01). IRL 1620 (Suc-[Glu9, Ala11,15]endothelin-1-(8-21), agonist for endothelin ET(B) receptors, 0.01-0.3 nmol) slightly decreased cerebral blood flow. The effects of endothelin-1, but not those of IRL 1620, on cerebral blood flow were diminished by 50% during infusion of the antagonist for endothelin ET(A) receptors, BQ-123 (cyclo-(D-Asp-Pro-D-Val-Leu-Trp), 2 nmol min(-1)), but not affected during infusion of the antagonist for endothelin ET(B) receptors, BQ-788 (N-[N-[N-[(2,6-dimethyl-1-piperidinyl)carbonyl]-4-methyl-L-Leucyl-1-(met hoxycarbonyl)-D-tryptophyl]-Dnorleucine monosodium), 2 nmol min(-1)). Intravenous administration of NW-nitro-L-arginine methyl ester (L-NAME, 47 mg kg(-1)) or NW-nitro-L-arginine (L-NNA, 47 mg kg(-1)) reduced basal cerebral blood flow by 39 and 33%, increased cerebrovascular resistance by 108 and 98% and mean arterial pressure by 23 and 17%, and decreased heart rate by 27 and 25%, respectively (all at least P < 0.05). The increases in cerebrovascular resistance (as absolute values) induced by endothelin-1 were not affected during either L-NAME or L-NNA (as absolute values and percentages). Intravenous administration of meclofenamate (5 mg kg(-1)) did not change the cerebrovascular effects of endothelin-1 and IRL 1620. In isolated goat cerebral arteries under control, resting conditions, endothelin-1 (10(-11)-10(-7) M) induced concentration-dependent contractions (EC50 = 4.78 X 10(-9) M; maximal contraction = 3177+/-129 mg), whereas IRL 1620 (10(-11)-10(-7) M) produced no effect. This contraction produced by endothelin-1 was competitively blocked by BQ-123 (10(-7)-3 X 10(-6) M), and was not affected by BQ-788 (10(-6) and 10(-5) M). L-NAME (10(-4) M), meclofenamate (10(-5) M), indomethacin (10(-5) M), L-NAME (10(-4) M) plus meclofenamate (10(-5) M) and phosphoramidon (10(-4) M) did not affect the contraction in response to endothelin-1. Endothelium removal increased the response to endothelin-1, as well as the BQ-123 antagonism against endothelin-1 (pA2 values, 7.62 vs. 6.88; P < 0.01). In both intact and de-endothelized arteries precontracted with prostaglandin F2alpha endothelin-1 induced a further contraction, and IRL 1620 caused no effect. These results suggest that: (1) endothelin-1 produces cerebral vasoconstriction by activating endothelin ET(A) receptors probably located in smooth muscle; (2) endothelin ET(B) receptors, nitric oxide and prostanoids might be not involved in the cerebrovascular action of endothelin-1, and (3) endothelium removal may increase cerebrovascular reactivity by increasing sensitivity of endothelin ET(A) receptors to endothelin-1.

Effects of verapamil on the renal actions induced by nitric oxide and prostaglandin synthesis inhibition

This study was designed to determine the effects of a calcium antagonist (verapamil) on the renal actions induced by nitric oxide synthesis inhibition, with and without simultaneous prostaglandin synthesis inhibition. The renal effects of verapamil (2 micrograms/kg/min) were examined in anesthetized dogs before and after an increase of extracellular volume and during the reduction of nitric oxide synthesis (1 microgram/kg/min NG-nitro-L-arginine methyl ester [L-NAME]), with and without the administration of a cyclooxygenase inhibitor (5 micrograms/kg/min meclofenamate). Nitric oxide synthesis inhibition produced an increase in proximal sodium reabsorption (lithium clearance technique) and a decrease in the excretory response to volume expansion that was prevented by the administration of verapamil. The administration of a cyclooxygenase inhibitor, during nitric oxide synthesis inhibition, elicited an increase in arterial pressure, an important renal vasoconstriction, and reduced the renal excretory response to volume expansion. The antinatriuretic effect produced by the simultaneous reduction of nitric oxide and prostaglandin synthesis, before and after the volume expansion, was abolished with the verapamil infusion. However, the increase of arterial pressure and renal vasoconstriction were only partly affected by verapamil. We found that the antinatriuretic effect secondary to the reduction of nitric oxide synthesis, during an increase in extracellular volume, is prevented by the administration of verapamil. Additionally, the administration of verapamil completely prevents the antinatriuretic, but not the vasoconstrictor, effects induced by the administration of a cyclooxygenase inhibitor when nitric oxide is slightly reduced.

Influence of closure of the reticular groove on the bioavailability and disposition kinetics of meclofenamate in sheep

Sodium meclofenamate is a non-steroidal anti-inflammatory drug with anaphylactic protective activity in cattle. The objectives of this study were to describe the pharmacokinetic behaviour of sodium meclofenamate after intravenous and oral administration to sheep and to determine the influence of closure of the reticular groove on the bioavailability of the drug. Sodium meclofenamate was administered by the intravenous (2.2 mg/kg) and oral (20 mg/kg) routes to sheep (n = 6). During the oral study the reticular groove was closed by intravenous administration of lysine vasopressin (0.3 IU/kg) or left open (saline solution). The closure of the reticular groove was assessed by determination of the blood glucose curves after oral administration of a glucose solution. After intravenous administration of meclofenamate, the distribution and elimination half-lives of the drug were 7.2 min and 542 min respectively, Vss was 1.68 L/kg and ClB was 2.47 mliter/min kg. Two different patterns of the plasma concentration curves were observed after oral administration of sodium meclofenamate. When the reticular groove was closed, two peaks were observed (tmax-1 12-15 min, Cmax-1 3.30-24.01 micrograms/mliter; and tmax-2' 52.50-75 min, Cmax-2, 6.45-11.08 micrograms/mliter).

Comparison of the kinetics of sodium meclofenamate versus meclofenamic acid after oral administration to sheep

Meclofenamates are non-steroidal anti-inflammatory agents used in ruminants for the prevention and the treatment of anaphylactic processes. The objective of the present work was to study possible kinetic variations due to the chemical form of meclofenamates administered by the oral route to adult sheep. Six Rubia del Molar female sheep (2-3 years old, 47-57 kg) were used. Initially, an intravenous administration of sodium meclofenamate (2.2 mg/kg bwt) was given; the obtained kinetic results were in agreement with data from other authors. Oral administrations (20 mg/kg bwt) of sodium meclofenamate and meclofenamic acid were then given. When the reticular groove was opened, both drug forms showed a single meclofenamate plasma peak; t2max were 60.0 +/- 10.61 min and 127.50 +/- 22.5 min for the sodium and acid form, respectively. The elimination rate constants (beta) were not significantly different, but the absorption half-lives were (14.69 +/- 3.21 min for the sodium form and 61.07 +/- 21.7 min for the acid form). The bioavailability was 48.6 +/- 4.3% for sodium meclofenamate and 65.1 +/- 2.8% for meclofenamic acid. Thus, the chemical form (sodium versus acid) alters the oral bioavailability and tmax of meclofenamates in adult sheep. These findings agree with the behaviour of meclofenamates in man.

Single dose and multidose analgesic study of ibuprofen and meclofenamate sodium after third molar surgery

The purpose of this study was to compare the analgesic efficacy and safety of meclofenamate sodium with ibuprofen after dental impaction surgery. This study was double-blind and used a unique methodology. Patients (N = 254) were first randomized into the single dose phase of the study that included placebo, meclofenamate 50 mg, meclofenamate 100 mg, ibuprofen 200 mg, and ibuprofen 400 mg, followed by a 7-day multidose phase in which patients in the placebo group were rerandomized into one of the active treatment cells. In the single dose phase, all active treatments were significantly more efficacious than placebo for every summary analgesic measure. A positive dose-response was seen for both active drugs with meclofenamate 100 mg and ibuprofen 400 mg exhibiting the greatest efficacy for pain relief, pain reduction, time to remedication, and overall evaluation. Side effects were reported by 26 patients. They were evenly distributed among treatment groups with headache and drowsiness being the most common. During the multidose phase, there were only small differences in efficacy measures among active treatment groups. However, meclofenamate produced a higher incidence of stomach cramps and diarrhea than did ibuprofen (8.8% and 7.2% versus 0.8% and 0.8%). This study indicates that higher doses of nonsteroidal anti-inflammatory drugs are most effective immediately after surgery and that lower doses of these drugs can be used after the first postoperative day. The side effect profile of nonsteroidal anti-inflammatory analgesics is best observed with the use of a multidose study design.

Efficacy of meclofenamate sodium (Meclomen) in the treatment of rapidly progressive periodontitis

This 6-month, double-blind, controlled clinical trial determined the efficacy of the non-steroidal anti-inflammatory drug, meclofenamate sodium (Meclomen), as an adjunct to scaling and root planing in the treatment of rapidly progressive periodontitis (RPP). 22 subjects (7 male, 15 female) aged 36.5 +/- 7.88 years with RPP and disease-active sites as determined by pretreatment bone scan had standardized radiographs at baseline and 6 months, and clinical measurements at baseline, 3 and 6 months. Following full-mouth scaling and root planing, subjects were randomly assigned to either a placebo, 50 or 100 mg meclofenamate sodium bid group. Bone change over the 6-month period as assessed by subtraction radiography was the primary efficacy determinant. Specialized software was used to isolate the lesion from the subtraction image and to measure bone change along the root surface. ANOVA using the subject as the unit of analysis revealed a significant dose response (p < 0.001) with the placebo group having a mean bone loss of 0.42 +/- 0.06 mm and the low and high dose groups having mean bone gains of 0.07 +/- 0.05 and 0.20 +/- 0.07 mm, respectively. These findings indicate that meclofenamate sodium may be a useful adjunct in the treatment of rapidly progressive periodontitis.

Identification of two different rate-limiting mechanisms controlling the release of NSAIDs from silastic polymeric devices, and possible implications

Two different rate-limiting mechanisms have been found by examining the release characteristics of meclofenamic acid, BW755C.hydrochloride, and diclofenac sodium from silastic polymeric rods into phosphate (0.1 M, pH 7.3) at 37 degrees C. Experiments were performed using rods with initial drug concentrations of 3, 6 and 9% w/w and plots of Q-t and Q-t1/2 were made (Q, cumulative amount of drug released into solution; t, time). For each of the three loadings of meclofenamic acid, the Q-t1/2 plot was linear which indicated a matrix controlled release of the drug. With diclofenac sodium, each of the three loadings gave a Q-t plot that was linear thereby indicating a partition controlled release of this drug. For BW755C.HCl, the release of the drug from rods at the two lowest loadings was matrix controlled, but release from rods at the highest loading was partition controlled. The possible implications of these findings are discussed in regard to medicated vaginal devices or intracervical devices.

Studies of meclofenamic acid and two metabolites in horses--pharmacokinetics and effects on exercise tolerance

The pharmacokinetics and the effects on treadmill exercise of the anti-inflammatory drug meclofenamic acid were studied in seven Standardbred horses after single intravenous and/or oral doses. The decline in plasma concentration after a single intravenous dose of meclofenamic acid (2.2 mg/kg b.wt) was described by a two-compartment open model. The average elimination half-life was 1.4 h, the apparent volume of distribution 0.14 l/kg and the plasma clearance 0.12 l/h kg. Absorption was the rate-limiting step after oral administration. Non-compartmental analysis showed a mean absorption time of 4.3 h. The pharmacokinetics of two metabolites of meclofenamic acid were also studied in two of the horses. The elimination half-lives of the two metabolites were virtually the same in each horse (3.0 h and 3.4 h). The blood lactate response to exercise was significantly decreased after treatment with meclofenamic acid, indicating a lower utilization of the glycolytic ('anaerobic') energy contribution during exercise. Circulatory capacity was apparently unaffected with an unchanged heart rate response to exercise.

Effects of topical applications of meclofenamic acid and ibuprofen on bone loss, subgingival microbiota and gingival PMN response in the primate Macaca fascicularis

Nonsteroidal anti-inflammatory drugs (NSAIDs) have been shown to alter periodontitis in both animals and humans. This study was initiated in the nonhuman primate (Nhp) model to determine the effect of two NSAIDs on preexisting gingivitis, the conversion of gingivitis to periodontitis, the associated subgingival microbiota, and the gingival PMN response. Eighteen cynomolgus monkeys were divided into three groups and treated on a blind basis with ibuprofen 8%, meclofenamic acid 5%, or placebo applied topically 5 days/week for 20 wk. After 4 wk of treatment, periodontitis was initiated in one quadrant by the placement of silk ligatures. Clinical parameters, bone loss by densitometric analysis of radiographs (CADIA), and cultural microbiology of subgingival plaque were monitored. In situ PMN chemotaxis was assessed by quantitating the PMNs which entered the sulcus in response to a challenge with n-formyl-methionyl-leucyl-phenylalanine (FMLP). No significant differences in the clinical parameters were noted by treatment groups. Radiographic bone loss was detected in all experimental sites in placebo animals as compared with 67% and 44% for ibuprofen and meclofenamic acid animals, respectively. Mean CADIA scores/animal showed a significant loss in bone density for placebo at 6 and 16 wk, no change for ibuprofen animals, and a significant increase in density for meclofenamic acid animals. The microbiota of all groups changed with ligation consistent with previous reports of disease initiation in the Nhp.(ABSTRACT TRUNCATED AT 250 WORDS)

Double-blind comparison of meclofenamate sodium plus codeine, meclofenamate sodium, codeine, and placebo for relief of pain following surgical removal of third molars

A single-dose, randomized, double-blind, parallel-treatment study was performed in 200 outpatients with acute pain caused by the surgical removal of impacted third molars. Meclofenamate 100 mg plus codeine 60 mg, meclofenamate 50 mg plus codeine 30 mg, meclofenamate 100 mg, codeine 60 mg, and placebo treatment groups were compared for sum of pain intensity differences, peak pain intensity difference, sum of pain relief scores, peak pain relief, number of observations at which pain was half relieved, overall evaluation of effectiveness, and time to remedication with a backup analgesic. Meclofenamate 100 mg plus codeine 60 mg was significantly more effective (P less than .005) than codeine 60 mg for all variables except number of observations at which pain was half relieved. Both meclofenamate-codeine combinations and meclofenamate 100 mg alone were significantly more effective (P less than .005) than placebo for all variables. Eleven adverse experiences were reported in 7 patients (3.5%); the most common was somnolence in 1 patient receiving meclofenamate 100 mg plus codeine 60 mg, in 2 treated with meclofenamate 50 mg plus codeine 30 mg, and in 1 treated with codeine 60 mg.

A single and multiple dose pharmacokinetic and metabolism study of meclofenamate sodium

A single and multiple oral dose administration study of meclofenamate sodium (Meclomen) was conducted in ten healthy male volunteers. An initial 300 mg oral dose on day 1 was followed by a 100 mg every 8 h dosage regimen on study days 4 through 18. Intensive plasma and urine sample collection was carried out over the first three study days, and for 120 h following administration of the final dose on day 18. Plasma and urine specimens were analyzed by a specific HPLC assay for unconjugated meclofenamic acid and metabolites I and II of meclofenamic acid before and after sample incubation with beta-glucuronidase. Meclofenamic acid was rapidly absorbed following oral dose administration. Concentrations of meclofenamic acid existed primarily as unconjugated drug in plasma, with only a small amount present in the conjugated form. Meclofenamic acid was rapidly eliminated, with an elimination half-life of approximately 1.3 h. This resulted in no detectable accumulation upon multiple dose administration. Metabolite I, which is one-fifth as active as meclofenamic acid in in vitro inhibition of cyclooxygenase, was present in unconjugated form at steady state in concentrations approximately 50 per cent of those of meclofenamic acid, as unconjugated drug. The majority of metabolite I in plasma existed as glucuronide conjugate. Metabolite II, which is inactive, was present in very significant concentrations in unconjugated form. Plasma protein binding determinations conducted on meclofenamic acid and metabolite I indicated that the free fraction of metabolite I was 8.7 to 10.9 times higher than that of meclofenamic acid. When the lower activity and lower steady state concentrations, but higher free fraction, are considered, it would appear that metabolite I may contribute significantly to the in vivo inhibition of cyclooxygenase activity seen after administration of meclofenamic acid.

Intraluteal infusion of a prostaglandin synthesis inhibitor, sodium meclofenamate, causes premature luteolysis in rhesus monkeys

The physiological significance of locally produced prostaglandins (PGs) in the regulation of the functional lifespan of the primate corpus luteum is unknown. In the current study, the PG synthesis inhibitor sodium meclofenamate was administered to adult female rhesus monkeys beginning in the midluteal phase of the menstrual cycle. Meclofenamate was infused continuously for 7 days into the corpus luteum (100 micrograms/h, n = 6) or the jugular vein (100 micrograms/h, n = 3; 1000 micrograms/h, n = 3) via osmotic minipump. As controls, PBS was infused into the corpus luteum (n = 7) or jugular vein (n = 5). In some of the monkeys receiving intraluteal infusions, chronic aortic and utero-ovarian venous catheters were implanted, and blood samples were collected on alternate days for the measurement of PGE and PGF2 alpha by RIA. Saphenous venous blood was collected daily, and progesterone and cortisol levels were determined by RIA. LH levels were determined by the mouse Leydig cell bioassay. Progesterone levels over 5 days preceding treatment were not different among groups. A decline in progesterone levels on day 1 after surgery was observed in all treatment groups and was accompanied by a 1-day elevation in cortisol levels. Thereafter, five of seven monkeys who received intraluteal infusions of PBS displayed normal progesterone patterns during treatment and normal luteal phase lengths of 15.4 +/- 1.2 days (mean +/- SEM). In six monkeys that received intraluteal infusions of meclofenamate, progesterone levels typically fell to less than 1 ng/ml within 72 h after initiation of infusion; progesterone levels during 7 days of intraluteal infusion were significantly lower (P less than 0.01) in meclofenamate- vs. PBS-treated monkeys. Meclofenamate infusion into the corpus luteum significantly shortened (P less than 0.01) the luteal phase to 10.5 +/- 1.0 days. In contrast, progesterone levels during 7 days of meclofenamate infusion into the jugular vein did not differ from those in PBS-treated monkeys, and the length of the luteal phase was unaltered. LH levels, measured daily, did not differ among groups either before or during treatment. Although an venous/arterial gradient in PGE was detected at the time of surgery, we were unable to detect a significant gradient across the ovary in PGE or PGF2 alpha at any time after surgery in monkeys treated with either PBS or meclofenamate. The present data suggest an obligatory luteotropic role for locally produced metabolites of arachidonic acid, but a physiological role for either PGE or PGF2 alpha in regulating the primate corpus luteum remains equivocal.

Comparison of meclofenamate sodium and hydrocortisone for controlling the postsurgical inflammatory response in rats

The effectiveness of meclofenamate sodium and hydrocortisone in alleviation of local postsurgical swelling and leukocytic infiltration was compared at two postsurgical intervals in 60 male Sprague-Dawley rats. Both drugs were effective at 24 hours after surgery. Ten doses of 2 mg meclofenamate sodium administered over a 5-day period were more effective in reducing leukocytic infiltration than six doses of 2 mg hydrocortisone administered over the same period. Neither the hydrocortisone nor the meclofenamate sodium at the dosage used adversely affected osteoid formation.

Plasma and synovial fluid meclofenamic acid concentrations in patients with rheumatoid arthritis of the knee

We have measured plasma and synovial fluid concentrations of meclofenamic acid at 2, 4, 8, and 12 h during steady-state administration (100 mg three times daily for 4-7 days). Paired plasma and synovial samples were obtained pre-treatment and at one of the above times in twelve patients with a diagnosis of rheumatoid arthritis. In addition, the extent of protein binding of meclofenamic acid was assessed in vitro in the pre-treatment plasma and synovial fluid specimens. Peak total concentrations of 1.73 and 0.86 micrograms.ml-1 were observed in plasma (at 2 h) and synovial fluid (at 4 h) respectively. The extent of protein binding was 99.7 and 99.6% (not significantly different) in plasma and synovial fluid respectively. The results of this study are compared to those from similar reported studies of other nonsteroidal anti-inflamatory compounds.

The topical anti-inflammatory effects of a topical preparation of meclofenamic acid on carrageenan-induced footpad swelling in mice

A topical preparation of meclofenamic acid (Meclomen) was tested for anti-inflammatory activity in a murine model of carrageenan footpad oedema. The preparation significantly inhibited swelling when applied to the carrageenan-injected paw. Maximum inhibition was observed 4-5 h after carrageenan injection. The topical effects could not be attributed to systemic absorption because the preparation was more inhibitory when applied topically to the carrageenan-injected paw than to a distant site or orally.

Analgesic efficacy of meclofenamate sodium in episiotomy pain

Meclofenamate sodium was compared, double-blind, with codeine and placebo for the treatment of acute episiotomy pain. One hundred sixty-eight women with moderate or severe episiotomy pain after normal delivery were assigned randomly to one of four treatment groups: one received meclofenamate sodium 200 mg at dose 1 and 100 mg at doses 2 and 3; one received meclofenamate sodium 100 mg at dose 1 and 50 mg at doses 2 and 3; one received codeine 60 mg at all three doses; and one received placebo at all three doses. Efficacy measurements were evaluated periodically for 6 hours after medication. After the first administration, both doses of meclofenamate sodium were significantly superior to placebo and to codeine from 2-6 hours in pain intensity difference and pain relief. For second and third doses, data were available for too few patients to allow valid analysis and interpretation. Adverse effects occurred in 4 patients in each meclofenamate sodium group, and in 8 in the codeine group and in 6 in the placebo group. The study indicates that single 100- and 200-mg doses of meclofenamate sodium are as safe as, and significantly more effective than, codeine 60 mg or placebo for episiotomy pain.

Effect of anti-inflammatory agents on the haemorrhagic response of mouse skin to Bordetella pertussis heat-labile toxin

Bordetella pertussis heat-labile toxin (HLT) was assayed by the haemorrhagic response produced by subcutaneous injection into weaned mice. Young mice, 3-5 weeks old of either sex, were highly responsive but they became resistant to HLT as they matured. Two anti-inflammatory agents, prednisolone and meclofenamate, inhibited the skin reactions in young mice. When given intraperitoneally, prednisolone was most inhibitory if it was injected just before, or at the same time as, HLT challenge. Prednisolone given 3 h after challenge, when the skin reactions had started to develop, did not significantly attenuate the final response. Both drugs were even more effective when mixed with the HLT challenge and injected subcutaneously. These findings are discussed in relation to the possible mechanism of action of HLT and to the reported beneficial effects of corticosteroids in the treatment of whooping cough.

Influence of steroidal and nonsteroidal anti-inflammatory agents on the accumulation of arachidonic acid metabolites in plasma and lung lymph after endotoxemia in awake sheep. Measurements of prostacyclin and thromboxane metabolites and 12-HETE

The influence of methylprednisolone and meclofenamate on endotoxin-induced release of 3 arachidonic acid metabolites was studied in unanesthetized sheep. Concentrations in plasma and lung lymph of prostacyclin and thromboxane (Tx) A2 metabolites (6-keto-PGF1 alpha and TxB2, respectively) were measured by radioimmunoassay. Concentrations of 12-HETE in lung lymph were measured by stable isotope dilution assay employing gas chromatography-mass spectroscopy. Thromboxane B2 concentrations increased quickly to peak values during the first hour after endotoxin infusion, then decreased to baseline by 1.5 hr. 6-keto-PGF1 alpha concentrations increased more gradually to peak values between 1 and 2 h after endotoxin infusion and remained elevated at 2.5 h. Lymph concentrations of both cyclooxygenase metabolites exceeded those in blood plasma. Methylprednisolone significantly inhibited accumulation of 6-keto-PGF1 alpha in lymph and plasma, but did not significantly inhibit accumulation of TxB2 in lymph or plasma. The combination of meclofenamate and methylprednisolone completely inhibited accumulation of TxB2 and 6-keto-PGF1 alpha in lymph and plasma. The concentration of 12-HETE in lung lymph increased significantly to peak values by 2.5 h after endotoxemia, and methylprednisolone, with or without meclofenamate, inhibited accumulation of 12-HETE in lung lymph. These data support participation of TxA2 in acute pulmonary hypertension after endotoxemia. That methylprednisolone treatment inhibited accumulation of 6-keto-PGF1 alpha and prevented the increase in lung vascular permeability suggests that prostacyclin production is a consequence of lung vascular injury. Increased lung lymph concentrations of the lipoxygenation product, 12-HETE, were coincident with physiologic evidence of increased lung vascular permeability, but whether release of lipoxygenase products after endotoxemia contributes to or results from lung vascular injury remains to be established.

Effects of oral meclofenamate therapy in psoriasis

One hundred three patients entered a study to evaluate the effects of oral meclofenamate sodium therapy on psoriasis. The first 4 weeks of the study were double-blind, with patients receiving either meclofenamate or placebo. Most patients receiving meclofenamate had no change in their psoriasis, in comparison with their pretherapy condition. There was no difference in the response of the psoriasis between the group taking meclofenamate and the group taking placebo. Eighty-nine patients continued in a 4-week open trial of meclofenamate. Approximately one third of the patients showed improvement, but this result appeared to be related to the open trial design. Since oral meclofenamate therapy was not associated with frequent worsening of psoriasis, it is an appropriate treatment for psoriatic arthritis.

Comparison of meclofenamate sodium with buffered aspirin and placebo in the treatment of postsurgical dental pain

The efficacy of meclofenamate sodium (Meclomen) at two different doses was compared with that of buffered aspirin and placebo in the control of postsurgical pain in a double-blind, randomized study of 205 patients. Meclofenamate sodium, 200 mg, was significantly better than meclofenamate sodium, 100 mg, in some efficacy parameters. Both doses of meclofenamate sodium were superior to buffered aspirin in most parameters of efficacy, and more effective than placebo in every parameter.

Non-steroidal anti-inflammatory drugs in combination. Experimental observations

Diflunisal in combinations with oxaprozin, indomethacin and sodium meclofenamate produced significant synergistic suppression of carrageenan-induced oedema of the rat foot-pad. Oxaprozin, benoxaprofen, indomethacin, diflunisal, sodium meclofenamate and auranofin in some paired combinations but not in others were associated with a greater effect than the component drugs used alone. Antagonism was demonstrated with other combinations of these drugs.

Methods for the treatment of twin pregnancy in the mare

Within a group of 130 mares which, in the event, carried twin pregnancies, 29 (22.3 per cent) produced their twins following diagnosis of a single palpable follicle at service and a single pregnancy 42 days later. The whole group of 130 twin-pregnant mares gave birth to only 17 live foals (13 per cent). Breeding results for the following season were available for 102 of these mares, when 38 (37 per cent) produced live foals. Thus over the two seasons an average 23 per cent of this group produced live foals. In a second group, comprising 70 mares, twin pregnancy had been diagnosed in all of them by rectal palpation. Five methods of treatment were then applied to five subgroups of mares and 20 (28 per cent) of the 70 mares produced live foals that season. Breeding results for the following season were available for 53 of these mares; 33 (61 per cent) then produced live foals. Thus over the two seasons an average 46 per cent of the treated group produced live foals. The administration of a prostaglandin analogue at less than 35 days of gestation was outstandingly successful as a method of treatment.

Factors affecting absorption of non-steroidal anti-inflammatory agents in the horse

The absorption of orally administered phenylbutazone (5 mg/kg) was studied in 10 thoroughbreds, eight ponies and four pony foals. Large variations in area under the curve (AUC) and peak plasma concentrations were found both within an animal and within groups of animals. Administration of phenylbutazone (5 mg/kg) following an overnight fast resulted in no difference among the three groups of animals with respect to AUC (0 to 24 hours), mean (+/- sd) values of which were 132 +/- 68, 107 +/- 48 and 98 +/- 6, respectively. Absorption characteristics of two oral phenylbutazone preparations (Equipalazone; Arnolds and Prodynam; Leo Laboratories) (5 mg/kg) given after an overnight fast were similar. Feeding before drug administration decreased AUC and peak plasma concentration and extended the range of the time taken to attain the latter. Repeated twice daily administration of phenylbutazone (5 mg/kg) resulted in more rapid absorption following the morning than the afternoon dose. Investigations with meclofenamic acid (4.4 mg/kg) also resulted in highest peak plasma concentrations and AUC following overnight fast. It was found that absorption was slower with intramuscular injections of phenylbutazone (2.5 mg/kg) than after oral administration in the fasted animal.

The pharmacokinetics of meclofenamic acid in the horse

The pharmacokinetics of meclofenamic acid were studied in Thoroughbred horses and in ponies. After intravenous (i.v.) administration of either 2 mg/kg or 4 mg/kg sodium meclofenamate the elimination half-life was of the order of 0.9 h while the volume of distribution was found to be 0.128 litre/kg. Elimination was in accordance with a one-compartment model. Following oral administration of either meclofenamic acid (4 mg/kg) or sodium meclofenamate (4 mg/kg) a much longer terminal half-life than that calculated for Kel from i.v. data was found. This anomaly indicated that the 'flip-flop' phenomenon was present, i.e. Ka exceeded Kel. More rapid and higher peak levels occurred following sodium meclofenamate than meclofenamic acid, although total bioavailability was similar. Studies in ponies with meclofenamic acid showed a lower absorption than that found in Thoroughbreds. Overnight fasting before meclofenamic acid administration did not alter the rate or extent of absorption. Intramuscular administration of sodium meclofenamate resulted in low plasma concentrations and after 25 h only 46% of the drug had been absorbed.

Effect of oral meclofenamic acid on uterine motility and reactivity to oxytocin in goats

Spontaneous uterine motility and reactivity to intravenous oxytocin were recorded in eight ovariectomised, oestrogen-primed goats before and after oral meclofenamic acid treatment. Spontaneous motility was completely abolished within 50 to 100 min of meclofenamate administration. However, although uterine reactivity to oxytocin was significantly reduced, the sensitivity was not altered. It is suggested that, in the goat, oxytocin has two effects on the uterus: it increases myometrial activity and also stimulates prostaglandin synthesis.

Cerebral vasodilation and prostacyclin. The effects of aspirin and meclofenamate in vitro

The effects of aspirin and meclofenamic acid on the diphasic responses produced by prostacyclin in isolated canine basilar arteries were compared. Meclofenamate enhanced the relaxant action of prostacyclin in low concentrations (10(-8)M to 10(-6)M) and also significantly inhibited the contractions caused by the highest concentration (10(-5)M) of this prostaglandin. Aspirin had no such effects. The results indicate that some drugs classified as prostaglandin synthetase inhibitors can directly enhance the vasodilator action of prostacyclin on cerebral arteries, and suggest that this enhancement could be of value in the clinical applications of prostacyclin.

Urinary prostaglandin E excretion: effect of chronic alterations in sodium intake and inhibition of prostaglandin synthesis in the rabbit

On the basis of acute experiments in animals, a role for prostaglandin E (PGE) in the regulation of urinary sodium excretion has been suggested. Limited information is available, however, concerning the possible role of PGE in chronic adjustments to sodium intake. These studies were designed to determine whether chronic changes in sodium balance would modify renal PGE excretion and whether partial inhibition of prostaglandin synthesis would alter the ability of the kidney to adjust to an alteration in sodium intake. Thus, we measured sodium and PGE excretion in rabbits on chronic high and low salt diets before and after inhibition of prostaglandin synthesis with indomethacin or meclofenamate. Although the alterations in salt intake resulted in large changes in sodium excretion there was no significant change in urinary PGE excretion. After administration of either indomethacin or meclofenamate for several days there was a significant fall in PGE excretion, but no significant change in sodium excretion. These results suggest that in the rabbit 1) chronic changes in sodium excretion can occur without modifying PGE excretion (and presumably renal PGE synthesis) and 2) inhibition of PGE synthesis does not impair the kidney's ability to adjust to a chronic high or low sodium intake.

Effect of meclofenamate on renal vascular resistance in early Goldblatt hypertension in conscious and anesthetized dog

Blood pressure and renal blood flow were monitored in conscious normotensive (N) and 2-kidney Goldblatt hypertensive (H) dogs. Plasma renin activity was signficantly increased 4--8 days after partial renal artery occlusion. At this time intravenous administration of meclofenamate, 5 mg/kg, had no effect on blood pressure in the N or H or on renal vascular resistance in the N or in the H (contralateral kidney). The renal vasoconstrictor response to angiotensin II was increased in duration by meclofenamate in both the N and H. In contrast to the absence of an effect of meclofenamate on renal vascular resistance in the conscious dog, the synthesis inhibitor caused a consistent increase in RVR in the N and H when they were anesthetized in the terminal experiment. These results suggest the lack of an influence of prostaglandins on renal vascular resistance in the unaffected kidney in Goldblatt hypertension.

Plasma levels following administration of sodium meclofenamate by various routes

Sodium meclofenamate, an anti-inflammatory and anti-anaphylactic agent, was administered to cattle intravenously, orally and by intraruminal injection. Plasma levels of the free drug were estimated fluorimetrically at intervals after administration by each route. Levels fell rapidly, particularly during the first hour after intravenous injection. Differences between those plasma levels resulting from oral administration and those following intraruminal injection indicated that direct passage into the abomasum was achieved by the former method. Simultaneous intravenous and intrauminal injections achieved immediate high plasma levels and maintained levels adequate for efficacy for 24 h.