Dose escalation of certolizumab pegol from 200 mg to 400 mg every other week provides no additional efficacy in rheumatoid arthritis: an analysis of individual patient-level data.

OBJECTIVE: To determine whether certolizumab pegol (CZP) dosage escalation from 200 mg to 400 mg every other week benefits some patients with rheumatoid arthritis (RA). METHODS: In the extension of the Rheumatoid Arthritis Prevention of Structural Damage 1 (RAPID 1) study into an open-label study, all patients received CZP 400 mg every other week in combination with methotrexate (MTX). Before the open-label phase of the study, patients had received CZP 200 mg or 400 mg every other week, or placebo every other week, as add-on therapy to MTX. The open-label study included those who had completed the RAPID 1 study (to week 52) and also those who had been withdrawn from the study (at week 16, due to inadequate response). At 12 weeks and 48 weeks after enrollment in the open-label study, changes in the Disease Activity Score in 28 joints (DAS28) were compared in dose-escalation patients (200 mg increased to 400 mg every other week) versus stable-dosage patients (400 mg every other week), using cumulative probability plots of individual patient-level data. RESULTS: In the group of patients who had completed the RAPID 1 study and had moderate or severe disease activity at entry into the open-label study, and in those who had been withdrawn early from the RAPID 1 study, the median DAS28 improvements 12 weeks after enrollment into the open-label study were similar in the dose-escalation and stable-dose groups. Individual patient-level data revealed no greater likelihood of response in the group of patients who received an increased dosage of CZP versus those in whom a stable dosage was maintained, whether they had completed the RAPID 1 study or had been withdrawn early. CONCLUSION: Although patient heterogeneity in clinical settings is acknowledged, the present results indicate that increasing the dose of CZP from 200 mg to 400 mg offers little additional benefit in RA, even for selected patients.

Hydroxylamine blocks pre- but not postsynaptic adenosine A(1) receptor-mediated actions in rat hippocampus.

The commonly used nitric oxide donor, hydroxylamine (NH(2)OH), can block or reverse the inhibition of glutamatergic transmission by adenosine or an adenosine A(1) agonist in rat hippocampal slice. In these experiments, hydroxylamine did not affect the adenosine A(1) receptor-mediated depression of postsynaptic excitability. We conclude that hydroxylamine acts presynaptically to counter adenosine A(1) receptor-mediated inhibition of synaptic transmission.

Hydroxylamine blocks adenosine A1 receptor-mediated inhibition of synaptic transmission in rat hippocampus.

The nitric oxide donor hydroxylamine (NH2OH) induced a transient depression of the evoked synaptic potential recorded in the rat hippocampal CA1 region. This depression was abolished with an adenosine A1 antagonist, 8-cyclopentyltheophylline. In addition, hydroxylamine reversed adenosine A1 receptor-mediated inhibition of the evoked population spike, the fEPSP and the intracellularly recorded EPSP. The inhibitory modulation of adenosine A1 receptor activation by hydroxylamine suggests the presence of a potent endogenous regulatory site.

Systemic hypoxia and the depression of synaptic transmission in rat hippocampus after carotid artery occlusion.

The relationship between step reductions in inspired oxygen and the amplitude of evoked field excitatory postsynaptic potentials (fEPSPs) recorded from hippocampal CA1 neurons was examined in anaesthetized rats with a unilateral common carotid artery occlusion. The amplitudes of fEPSPs recorded from the hippocampus ipsilateral to the occlusion were significantly more depressed with hypoxia than were the fEPSPs recorded from the contralateral hippocampus. The adenosine A1-selective antagonist, 8-cyclopentyl-1,3-dimethylxanthine (8-CPT), blunted the hypoxic depression of the fEPSP. Tissue partial pressure of oxygen (Ptiss,O2) was measured in the ipsilateral and contralateral hippocampus using glass Clark-style microelectrodes. Ptiss,O2 fell to similar levels as a function of inspired oxygen in the ipsilateral and contralateral hippocampus, and in the ipsilateral hippocampus after administration of 8-CPT. Hippocampal blood flow (HBF) was measured using laser Doppler flowmetry. A decline in HBF was associated with systemic hypoxia in both hippocampi. HBF, as a function of inspired oxygen, fell significantly more in the ipsilateral than in the contralateral hippocampus. We conclude that endogenous adenosine acting at the neuronal A1 receptor plays a major role in the depression of synaptic transmission during hypoxic ischaemia. The greater susceptibility of the fEPSP in the ipsilateral hippocampus to systemic hypoxia cannot be explained entirely by differences in Ptiss,O2 or HBF between the two hemispheres.

The effect of acute hypoxemia and hypotension on adenosine-mediated depression of evoked hippocampal synaptic transmission.

The present study was designed to investigate the relative contributions of arterial P(O(2)), local cerebral blood flow, and oxygen delivery to the adenosine A(1) receptor-mediated depression of evoked synaptic transmission recorded in the rat hippocampus. Urethane-anesthetized rats were given a unilateral common carotid artery occlusion and then placed in a stereotaxic apparatus for stimulation and recording of bilateral hippocampal field excitatory postsynaptic potentials (fEPSPs). Arterial blood gases, mean arterial blood pressure (MAP), and bilateral hippocampal blood flow (HBF) were also measured. Arterial P(O(2)), HBF, and oxygen delivery were manipulated using normoxic hypotension, hypoxic hypotension, and hypoxic normotension. Both hypoxic hypotension and normoxic hypotension resulted in decreased HBF, decreased oxygen delivery, and a depression of the evoked fEPSP limited to the hippocampus ipsilateral to the occlusion. The enhanced HBF and oxygen delivery associated with increased MAP resulted in a restoration and maintenance of hippocampal fEPSPs despite sustained hypoxemia. The adenosine A(1) receptor-mediated depression of the fEPSP was more strongly correlated with changes in HBF and oxygen delivery than with arterial P(O(2)). We propose that adenosine plays an important role mediating the depression of neuronal activity associated with reduced oxygen delivery characteristically observed in ischemic brain tissue.

Adenosine induces initial hypoxic-ischemic depression of synaptic transmission in the rat hippocampus in vivo.

The present study was designed to investigate the role of adenosine in the hypoxic depression of synaptic transmission in rat hippocampus. An in vivo model of hypoxic synaptic depression was developed in which the common carotid artery was occluded on one side in the urethane-anesthetized rat. Inspired oxygen levels were controlled through a tracheal cannula. Rats were placed in a stereotaxic apparatus for stimulation and recording of bilateral hippocampal field excitatory postsynaptic potentials. The percent inspired oxygen could be reduced to levels that produced a reversible and repeatable depression of evoked synaptic transmission restricted to the hippocampus ipsilateral to the occlusion. Further reduction in the level of inspired oxygen depressed synaptic transmission recorded from both hippocampi. The adenosine nonselective antagonist caffeine and the A(1) selective antagonist 8-cyclopentyltheophylline prevented the initial depression in synaptic transmission. We conclude that the initial depression of synaptic transmission observed in the rat hippocampus in vivo is due to endogenous adenosine acting at neuronal adenosine A(1) receptors.