Effect of indomethacin on cerebral blood flow, carbon dioxide reactivity and the response to epoprostenol (prostacyclin) infusion in man

Elevated prostacyclin biosynthesis in mice impacts memory and anxiety-like behavior

Prostacyclin is an endogenous lipid metabolite with properties of vasodilation and anti-platelet aggregation. While the effects of prostacyclin on the vascular protection have been well-documented, the role of this eicosanoid in the central nervous system has not been extensively studied. Recently, a transgenic mouse containing a hybrid enzyme, of cyclooxygenase-1 linked to prostacyclin synthase, was developed that produces elevated levels of prostacyclin in vivo. The goal of this study was to investigate whether increased prostacyclin biosynthesis could affect behavioral phenotypes in mice. Our results uncovered that elevated levels of prostacyclin broadly affect both cognitive and non-cognitive behaviors, including decreased anxiety-like behavior and improved learning in the fear-conditioning memory test. This study demonstrates that prostacyclin plays an important, but previously unrecognized, role in central nervous system function and behavior.

Effect of non-steroid anti-inflammatory drugs on neurovascular coupling in humans

BACKGROUND/AIMS

Neuronal activation induced cerebral blood flow increase was shown in animal experiments to require the presence of functioning cyclooxygenase. Our aim was to study whether widely used, non-steroid anti-inflammatory drugs (NSAIDs), given orally in usual therapeutic doses, inhibit neurovascular coupling in humans.

METHODS

By using a visual cortex stimulation paradigm, the flow velocity response was measured by transcranial Doppler sonography in both posterior cerebral arteries of fifteen young healthy adults. The investigation was repeated in the same subjects after 2-day administration of 3×25 mg indomethacin (indomethacin phase) and 2×550 mg naproxen (naproxen phase). Visual-evoked-potentials were also recorded during the control phase and after administration of NSAIDs.

RESULTS

Basal flow velocity significantly decreased while the pulsatility index increased after administration of either indomethacin or naproxen (p<0.01). Despite unchanged visual-evoked-potentials, the visually evoked flow velocity increase (26±7% in the control phase) significantly declined after administration of indomethacin (19±5%; p<0.01) or naproxen (20±5%; p<0.02).

CONCLUSION

Oral administration of indomethacin or naproxen in their usual therapeutic doses significantly impaired the resting and the visually evoked blood flow regulations in healthy human subjects. Together with stable evoked potentials, our findings indicate disturbance of neurovascular coupling.

Effect of indomethacin on cerebrovascular reactivity in patients with type 2 diabetes mellitus

AIM

Impaired cerebral vasoreactivity to endothelium-dependent stimuli were described in type 2 diabetes mellitus (T2DM), but the mechanisms underlying that impairment are still unclear. The aim of this study was to investigate the role of cyclooxygenases' metabolites in response to acute hypercapnic stimulus in cerebral vessels, in patients with T2DM.

METHODS

Vascular responses in the breath-holding test (BHT) were assessed in the absence/presence of a non-selective, reversible-inhibitor of cyclooxygenases, indomethacin (INDO), by functional transcranial Doppler sonography of the middle cerebral artery (N of patients=50; 33 men and 17 women). The functional hemodynamic parameter mean flow velocity (MFV) was assessed at rest, before and 90min after 100mg of INDO, and during the BHT. Breath holding index (BHI) [(MFV at the end of BHT minus MFV at rest)/MFV at rest)×100/s of breath-holding] was calculated after BHT performed before and 90min after INDO.

RESULTS

MFV at rest significantly decreased after INDO administration compared with a control condition before INDO (at rest before INDO from 49.36±15.09 to 36.72±8.45 after INDO, p<0.001) However, overall cerebral vessel vasoreactivity to hypercapnia, evaluated with BHI, was significantly improved after INDO administration compared with the BHI before INDO administration (from 0.68±0.4 to 1.27±0.42, p<0.001).

CONCLUSIONS

The improvement in cerebral vasoreactivity in response to BHT after INDO administration suggests that the production of a vasoconstrictor metabolite of cyclooxygenase in diabetic patients was reduced by indomethacin consumption.

Cyclooxygenase inhibition abolishes age-related differences in cerebral vasodilator responses to hypercapnia

Blood flow and vasodilatory responses are altered by age in a number of vascular beds, including the cerebral circulation. To test the role of prostaglandins as regulators of cerebral vascular function, we examined cerebral vasodilator responses to CO(2) (cerebrovascular reactivity) in young (26 ± 5 yr; 6 males/6 females) and older (65 ± 6 yr, 5 males/5 females) healthy humans before and after cyclooxygenase inhibition (using indomethacin). Middle cerebral artery velocity (MCAv) responses to stepped hypercapnia were measured before and 90 min after indomethacin. Changes in MCAv during the recovery from hypercapnia (vasoconstrictor responses) were also evaluated before and after indomethacin. Cerebrovascular reactivity was calculated using linear regression between MCAv and end-tidal CO(2). Young adults demonstrated greater MCAv (55 ± 6 vs. 39 ± 5 cm/s: P < 0.05) and MCAv reactivity (1.67 ± 0.20 vs. 1.09 ± 0.19 cm·s(-1)·mmHg(-1); P < 0.05) to hypercapnia compared with older adults (P < 0.05). In both groups MCAv and MCAv reactivity decreased between control and indomethacin. Furthermore, the age-related differences in these cerebrovascular variables were abolished by indomethacin. During the recovery from hypercapnia, there were no age-related differences in MCAv reactivity; however, indomethacin significantly reduced the MCAv reactivity in both groups. Taken together, these results suggest that cerebral blood flow velocity and cerebrovascular reactivity are attenuated in aging humans, and may be due to a loss of prostaglandin-mediated vasodilation.

Role of prostanoids in the regulation of cerebral blood flow during normoxia and hypoxia in the fetal sheep

The fetal cardiovascular responses to hypoxia include decreased peripheral blood flow and increased cerebral, cardiac, and adrenal blood flow. Prostanoids, metabolites of cyclooxygenase enzyme activity, have potent effects on vascular tone in both the adult and the fetus. To examine the role of prostanoids in the regulation of fetal cerebral blood flow (CBF) during acute hypoxic stress, eight near term fetal sheep were studied after infusing vehicle or diclofenac, a cyclooxygenase inhibitor, followed by a 30-min period of hypoxia (arterial Po(2) 12 Torr). In the control experiments, CBF, measured continuously with laser Doppler flowmetry, increased to 148% of baseline values (p < 0.01) and cerebral vascular resistance decreased to 70% of baseline values after 30 min of hypoxic stress. During diclofenac infusion, hypoxia resulted in a CBF increase to only 129% of baseline, a significant attenuation (p < 0.05), accompanied by decreased plasma prostanoid concentrations. Increases in mean arterial blood pressure during hypoxia were also attenuated by diclofenac infusion. Flow and pressure responses were not accompanied by changes in cerebral vascular resistance. These results indicate that prostanoids indirectly modulate fetal CBF responses to hypoxia, but that their effects are mediated through modulation of systemic rather than cerebral vascular tone.

Posterior hypothalamic activation in paroxysmal hemicrania

OBJECTIVE

Paroxysmal hemicrania (PH) is a severe, strictly unilateral headache that lasts 2 to 30 minutes, occurs more than five times daily, is associated with trigeminal autonomic symptoms, and is exquisitely responsive to indomethacin. The purpose of the study was to determine the brain structures active in PH.

METHODS

Seven PH patients were studied using positron emission tomography (PET). Each patient was scanned in three states: (1) acute PH attack-off indomethacin; (2) pain-free-off indomethacin; and (3) pain-free after administration of intramuscular indomethacin 100 mg. The scan images were processed and analyzed using SPM99.

RESULTS

The study showed no significant activations during state 1 compared with state 2, but there was relative activation of the pain neuromatrix in both states 1 and 2 compared with state 3. This suggests that there is persistent activation of the pain neuromatrix during acute PH attacks and during interictal pain-free states off indomethacin that is deactivated by the administration of indomethacin. In addition, the untreated PH state was associated with significant activation of the contralateral posterior hypothalamus and contralateral ventral midbrain, which extended over the red nucleus and the substantia nigra.

INTERPRETATION

These activated subcortical structures may play a pivotal role in the pathophysiology of this syndrome.

Treatment of elevated intracranial pressure with indomethacin: friend or foe?

Indomethacin has been suggested as a therapeutic tool to manage elevated intracranial pressure in patients with severe head injury and patients undergoing craniotomy for brain tumors. Indomethacin is a non-selective cyclooxygenase inhibitor. Compared to other cyclooxygenase inhibitors indomethacin has unique effects on cerebral blood flow. Administration of indomethacin causes cerebral vasoconstriction and decreases cerebral blood flow, which elicits a decrease in intracranial pressure. The mechanism of indomethacin-induced cerebral vasoconstriction is not completely understood and controversies exist whether indomethacin causes cerebral ischemia. The primary aims of this article were to review the existing knowledge of indomethacin's influence upon cerebral hemodynamics and elevated ICP in patients with brain pathology. Furthermore, indomethacin's mechanism of action and whether it causes cerebral ischemia are discussed.

Intravenous administration of flurbiprofen does not affect cerebral blood flow velocity and cerebral oxygenation under isoflurane and propofol anesthesia

Flurbiprofen, a nonsteroidal antiinflammatory drug (NSAID), has been used to treat rheumatic and osteoarthritic pain and to reduce postoperative pain. Although other NSAIDs, such as indomethacin, reduce cerebral blood flow (CBF), the effect of flurbiprofen on CBF is unknown. In the present study, we investigated the effects of flurbiprofen on cerebral blood flow velocity (CBFV) and cerebral oxygenation under isoflurane or propofol anesthesia. Forty-eight patients undergoing orthopedic or abdominal surgery were enrolled. Patients were randomly allocated to receive either propofol (target control infusion: target site effect concentration 3 microg/mL) or isoflurane (1 MAC) for maintenance of anesthesia. In each group (n = 12), 1 mg/kg of flurbiprofen (PROP-F and ISO-F groups) or 0.1 mL/kg saline (PROP-S and ISO-S groups) was administered i.v. for 5 min. During and after the administration of flurbiprofen or saline, cerebral oxygenation variables (tissue oxygen index [TOI], total hemoglobin change [Delta cHb], oxygenated hemoglobin changes [Delta O(2)Hb], and deoxygenated hemoglobin changes [Delta HHb]), and middle cerebral artery flow velocity (Vmca) were measured using a cerebral oximeter (NIRO 300) and transcranial Doppler, respectively, from 5 min before study drug administration to 60 min post-administration. Before the administration of flurbiprofen, control values of TOI in the ISO-S and ISO-F groups were significantly higher than those in the PROP-S and PROP-F groups, respectively (ISO-S versus PROP-S, 67% +/- 4% versus 60% +/- 7%; IOS-F versus PROP-F, 69% +/- 4% versus 63% +/- 8%; P < 0.05). However, values of TOI, Delta cHb, Delta O(2)Hb, Delta HHb, and Vmca did not change significantly during and after the administration of flurbiprofen under propofol or isoflurane anesthesia, and these values were similar to those during and after the administration of saline in the same anesthesia group. These data indicate that flurbiprofen does not affect CBFV and cerebral oxygenation under propofol or isoflurane anesthesia.

IMPLICATIONS

Indomethacin, a nonsteroidal antiinflammatory drug (NSAID), has been demonstrated to reduce cerebral blood flow (CBF). The CBF effects of flurbiprofen, another NSAID, are unknown. We investigated cerebral blood flow velocity (CBFV) and cerebral oxygenation during and after the administration of flurbiprofen under isoflurane and propofol anesthesia. We found that flurbiprofen had no effect on CBFV and cerebral oxygenation.

Effects of indomethacin on cerebral blood flow at rest and during hypercapnia: an arterial spin tagging study in humans

PURPOSE

To investigate using an arterial spin tagging (AST) approach the effect of indomethacin on the cerebral blood flow (CBF) response to hypercapnia.

MATERIALS AND METHODS

Subjects inhaled a gas mixture containing 6% CO(2) for two 5-minute periods, which were separated by a 10-minute interval, in which subjects inhaled room air. In six subjects, indomethacin (i.v., 0.2 mg/kg) was infused in the normocapnic interval between the two hypercapnic periods.

RESULTS

Indomethacin reduced normocapnic gray matter CBF by 36 +/- 5% and reduced the CBF increase during hypercapnia from 43 +/- 9% to 16 +/- 5% in gray matter (P < 0.001) and from 48 +/- 11% to 35 +/- 9% in white matter (P < 0.025).

CONCLUSION

The results demonstrate that an AST approach can measure the effects of indomethacin on global CBF increases during hypercapnia and suggest that an AST approach could be used to investigate pharmacological effects on focal CBF increases during functional activation.

Gender-related effects of indomethacin on cerebrovascular CO2 reactivity

Prostaglandins are believed to play an important role in the regulation of resting cerebral blood flow and in the vasodilatory response to hypercapnia. Recently, we reported an increased CO2 reactivity (CR) in premenopausal women and, in the past, evidence has accumulated that estrogens might increase basal levels of prostaglandin secretion from endothelial cells. Therefore, one may speculate that gender differences in CR are possibly mediated by higher prostaglandin levels in women. Using transcranial Doppler sonography, we assessed CR before and 90 min after a single dose of 100 mg of indomethacin in 22 healthy volunteers (11 men, 11 women). Before intake of indomethacin, women had a significantly higher CR (4.53+/-0.49 vs. 3.61+/-0.74, P<0.01). Ninety minutes after indomethacin administration, CR decreased to 1.53+/-0.93 in women and 1.60+/-0.92 in men, respectively. The change of CR was 3.00+/-1.29 in women vs. 2.01+/-1.06 in men (P=0.07). For the entire study population, the decrease of CR was linearly correlated with the initial value of CR (rs=0.74, P<0.001). This gender-related difference possibly relates to higher prostaglandin levels as mediators of an increased CR in premenopausal women, although the exact features remain to be clarified.

Dependence of basal cerebral blood flow and cerebral vascular resistance in spontaneously hypertensive rats upon vasoconstrictor prostanoids

The effects of indomethacin (inhibitor of cyclooxygenase), imidazole (inhibitor of thromboxane A2 synthase) and SQ 29548 (antagonist of TxA2/PGH2 receptors) on basal CBF and CVR were studied in normocapnic and normoxic SHR and WKY rats. CBF was measured by the intracarotid 133Xe technique. CVR was calculated as ratio of mean arterial blood pressure and CBF. Resting CBF did not differ between SHR and WKY. MABP and CVR were significantly higher (p < 0.01) in SHR than in WKY. Indomethacin (6 mg/kg, i.v.) produced a significant long-lasting decrease of CBF and increase of CVR in both strains, although these effects were more pronounced (p < 0.01) in WKY. Imidazole (20 mg/kg, i.v.) had no effect on measured variables in either strain. SQ 29548 (1 mg/kg, i.v.) produced a significant increase of CBF in SHR (p < 0.001) but not in WKY. CVR decreased in SHR parallel to the increase of CBF but remained unchanged in WKY. Our results demonstrate that, in contrast to WKY, basal CBF and CVR in SHR depend upon vasoconstricting prostanoids which act on TxA2/PGH2 receptors but are distinct from thromboxane A2.

Indomethacin in the management of elevated intracranial pressure: a review

Elevated intracranial pressure occurs frequently in patients with severe head injury. A number of studies in recent years suggest that indomethacin may be useful in the management of elevated intracranial pressure. Indomethacin acts primarily by reducing cerebral blood flow and decreasing cerebral edema following head injury. This review summarizes the basic and clinical studies of the effects of indomethacin on cerebral blood flow, brain edema, and intracranial pressure. The pharmacology of indomethacin, and issues for future investigation in the use of indomethacin in severe head injury, are discussed.

Differential effect of three cyclooxygenase inhibitors on human cerebral blood flow velocity and carbon dioxide reactivity

BACKGROUND AND PURPOSE

Prostaglandins are believed to play an important role in maintenance of cerebral blood flow and possibly in the vasodilatory response to carbon dioxide. Therefore, the nonsteroidal anti-inflammatory drugs and aspirin, which inhibit cyclooxygenase, might be expected to reduce cerebral blood flow and the response to hypercapnia. This could induce cerebral ischemia in patients with a hemodynamically critical circulation. It would also interfere with the measurement of cerebrovascular reserve using carbon dioxide.

METHODS

The effect of a single dose of indomethacin and of two other cyclooxygenase inhibitors (aspirin and sulindac) on the cerebral circulation was measured using transcranial Doppler ultrasonography of the middle cerebral artery. Seven normal adults were studied in each drug group. Resting blood flow velocity and the responses to hypercapnia and to hyperventilation were measured.

RESULTS

Indomethacin resulted in a fall in basal middle cerebral artery flow velocity from a mean of 48.9 cm/s to 34.0 cm/s (P < .002). It also reduced the vasoconstrictor response to hypocapnia (induced by hyperventilation) from 37.5% to 20.7% (P < .003). There was a nonsignificant reduction in the vasodilatory response to 8% carbon dioxide (mean: predrug, 87.7%; postdrug, 61.0%), with marked intersubject variability. In contrast, basal middle cerebral artery velocity and vasoconstrictor and vasodilatory responses to changes in carbon dioxide were unchanged after aspirin or sulindac administration.

CONCLUSIONS

The lack of effect of aspirin on basal cerebral blood flow velocity and on vasodilatory reserve is reassuring; aspirin will not reduce cerebral blood flow or the response to a reduced perfusion pressure in patients with critically impaired cerebral hemodynamics. However, indomethacin should be avoided in such patients.

Effects of indomethacin on myogenic contractile activation and responses to changes in O2 and CO2 in isolated feline cerebral arteries

We used an isolated, pressurized, and perfused feline middle cerebral artery preparation to measure how changes in intraluminal pressure and alterations in O2 and CO2 affect vessel diameter and myogenic contractile activation before and after treatment with indomethacin (IND). Vessel diameters were measured over the pressure range 60-140 mm Hg. The arteries were then exposed to low O2 (50 torr) and/or high CO2 (65 torr) and diameters remeasured over the same range. Under control conditions, the arteries exhibited myogenic contractile activation. Exposure to low O2, high CO2, or a mixture of low O2/high CO2, increased vessel diameter but did not change the vessels' myogenic contractile responsiveness to changes in pressure. Arteries exposed to IND decreased in diameter but retained myogenic contractile activity. In the presence of IND, vessels dilated to both low O2 and a mixture of low O2/high CO2, but did not dilate to high CO2 alone. Under all conditions, vessels retained myogenic contractile activity. Results obtained under control conditions and low O2 confirm those of others using similar systems. Myogenic contractile activity in the presence of high CO2 or a mixture of low O2/high CO2 has not been previously reported. The dilation to low O2 but not to high CO2 in the presence of IND suggests that this drug's effects in cerebral arteries are not limited solely to inhibition of prostaglandin synthesis.

Periventricular haemorrhage: association with patent ductus arteriosus and its treatment with indomethacin or surgery

A prospective study on 150 infants with a birthweight of 1250 g or less was carried out to investigate the effects of patent ductus arteriosus (PDA), haemorrhagic pulmonary oedema (HPO), Indomethacin therapy and surgical ligation on the development of periventricular haemorrhage (PVH) or the extension of pre-existing PVH. The incidence of PVH, diagnosed by serial cerebral ultrasonography was 44% and the incidence of PDA, diagnosed by serial M-mode and contrast echocardiography, was 45%. During the first 8 days after birth when the infants were vulnerable to PVH, the development of PDA did not lead to the development or extension of PVH in 85% of infants. Haemorrhagic pulmonary oedema also had no effect on PVH in 71% of infants. Compared with infants whose PDA or HPO had no effect on PVH, those who had development or extension of haemorrhage had significantly more severe hypercapnia, blood gas instability and hypotension associated with the occurrence of PDA or HPO. Early Indomethacin therapy was not associated with the development or extension of PVH in 93% of infants. Although an elevation of arterial blood pressure was demonstrated after ductal ligation, surgery was performed after 1 week of age in all infants and in no instance was there an effect on PVH. This study suggests that PDA leads to PVH only if it causes significant blood gas and blood pressure disturbances which are known to affect cerebral blood flow adversely.

Possible non-involvement of lipoxygenase pathway in the cerebral blood flow decrease due to indomethacin

Indomethacin (10n mg/kg i.p.) induced a marked decrease in local cerebral blood flow (l.CBF), which was measured in the frontal cortex of unanesthetized rats by the hydrogen clearance technique. Brain prostaglandins (PGD2, PGE2, PGF2 alpha,) and 6kPGF1 alpha the stable metabolite of prostacyclin, were significantly decreased. Treatments with inhibitors of lipoxygenase (BW 755C and nordihydroguaiaretic acid) and with FPL 55712, a leukotriene receptor antagonist, did not influence the effect of indomethacin on 1.CBF. The results suggest that the release of vasoconstrictory leukotrienes does not play a major role in the lowering of 1.CBF by indomethacin.