The use of flunarizine in the management of low-tension glaucoma: a color Doppler study

The Role of Magnesium in the Pathogenesis and Treatment of Glaucoma

Glaucoma is characterized by chronic optic neuropathy resulting in progressive vision loss. Not only is glaucoma considered as a condition of elevated intraocular pressure (IOP), but also other risk factors may play a role in the pathogenesis of glaucomatous optic nerve damage. Vascular dysregulation in ocular blood flow and oxidative stress are currently suggested as important risk factors for glaucomatous retinal ganglion cell loss. New treatment modalities that improve ocular blood flow and reduce oxidative stress have been investigated in many studies. Magnesium (Mg) is thought to be one of the molecules that has a treatment potential in glaucoma. Mg has been shown to improve blood flow by modifying endothelial function via endothelin-1 (ET-1) and endothelial nitric oxide (NO) pathways. Mg also exhibits neuroprotective role by blocking N-methyl-D-aspartate (NMDA) receptor-related calcium influx and by inhibiting the release of glutamate, and hence protects the cell against oxidative stress and apoptosis. Both improvement in ocular blood flow and prevention of ganglion cell loss would make magnesium a good candidate for glaucoma management. Further studies on the effect of Mg may open a new therapeutic era in glaucoma.

Current primary open-angle glaucoma treatments and future directions

Primary open-angle glaucoma (POAG) is a leading cause of blindness with no known cure. Management of the disease focuses on lowering intraocular pressure (IOP) with current classes of drugs like prostaglandin analogs, beta-blockers, alpha-agonists, and carbonic anhydrase inhibitors. These treatments have not helped all patients. Some patients continue to experience deterioration in the optic nerve even though their IOPs are within the normal range. New views have surfaced about other pathophysiological processes (such as oxidative stress, vascular dysfunction, and retinal cell apoptosis) being involved in POAG progression, and adjunctive treatments with drugs like memantine, bis(7)-tacrine, nimodipine, and mirtogenol are advocated. This review examines the current and proposed treatments for POAG. Some of the proposed drugs (bis(7)-tacrine, nimodipine, vitamin E, and others) have shown good promise, mostly as monotherapy in various clinical trials. It is recommended that both the current and proposed drugs be put through further robust trials in concurrent administration and evaluated.

Effect of nimodipine on ocular blood flow and colour contrast sensitivity in patients with normal tension glaucoma

AIM

To investigate the effects of oral nimodipine on ocular haemodynamic parameters and colour contrast sensitivity in patients with normal tension glaucoma (NTG).

DESIGN

The study was performed in a randomised, placebo controlled, double masked, crossover design.

PARTICIPANTS

Nimodipine (60 mg) or placebo was administered to 14 consecutive NTG patients.

METHODS

The effects or oral nimodipine or placebo on ocular and systemic haemodynamic parameters and colour contrast sensitivity along the tritan axis were studied two hours after administration. Optic nerve head blood flow (ONHBF) and choroidal blood flow (CHBF) were assessed with laser Doppler flowmetry. Ocular fundus pulsation amplitude (FPA) was measured with laser interferometry. Colour contrast sensitivity (CCS) was determined along the tritan colour axis.

MAIN OUTCOME MEASURES

ONHBF, CHBF, FPA, intraocular pressure and CCS were assessed in patients with NTG.

RESULTS

Mean ocular FPA increased by 14% (SD 14%) (p = 0.0008), ONHBF by 18% (SD 16%) (p = 0.0031), and CHBF by 12% (SD 14%) (p<0.001) after administration of nimodipine. Nimodipine also decreased the threshold of colour contrast sensitivity along the tritan colour axis (-14% (SD 12%); p = 0.048). However, individual changes in FPA, ONHBF, or CHBF were not correlated with changes in threshold of CCS along the tritan colour axis.

CONCLUSIONS

The results indicate that nimodipine increases ONH and choroidal blood flow in NTG patients and improves CCS. The latter effect does not, however, seem to be a direct consequence of the blood flow improvement.

Effects of betaxolol and flunarizine on visual fields and intraocular pressure in patients with migraine

Fifty-one patients with migraine were divided into four groups to investigate the effects of topical betaxolol and systemic calcium channel blocker flunarizine on visual fields (VF) and intraocular pressure (IOP). The first group (Group 0) was followed with no medications, topical betaxolol (bid) was precribed to the second group (Group B), oral flunarizine (10 mg daily) was prescribed to the third group (Group F), and the last group (Group BF) was assigned for combined betaxolol and flunarizine treatment. After a mean follow-up time of 4.2 +/- 1.2 months (3-6 months), IOP measurements and VF tests were repeated. Group B and Group BF were found to be statistically different from the other groups in terms of IOP reduction and VF improvement according to mean deviation and corrected pattern standard deviation indices in the second examinations. On the other hand, Group F and Group BF differed from the other two groups considering the improvement in migrainous complaints. VF findings which are probably influenced by perfusion problems due to vasospastic mechanisms in migraineurs, improved following topical betaxolol treatment. However, systemic use of flunarizine--a calcium channel blocker--did not seem to be effective on visual fields although it had beneficial effects on migraine.

Effect of lomerizine, a new Ca(2+)channel blocker, on the microcirculation in the optic nerve head in conscious rabbits: a study using a laser speckle technique

We examined the effect of a new Ca(2+)channel blocker, lomerizine (KB-2796), and compared it with that of nilvadipine, on the optic nerve head circulation in conscious rabbits using a laser speckle method. Lomerizine (0.03, 0.1 and 0.3 mg kg(-1), i.v.) and nilvadipine (0.003, 0.01 and 0.03 mg kg(-1), i.v.) each significantly increased the normalized blur values (an index of tissue blood velocity) in the optic nerve head in a dose-dependent manner. Neither lomerizine nor nilvadipine caused a significant change in intraocular pressure. Lomerizine produced no significant change in mean arterial blood pressure, although at 0.3 mg kg(-1), i. v. heart rate was significantly increased 5 min after its administration. In contrast, nilvadipine significantly decreased mean arterial blood pressure at 5 to 15 min after its administration and increased heart rate at 5-30 min after its administration (both effects being dose-dependent). Our results indicate that while lomerizine, like nilvadipine, increased tissue blood velocity in the optic nerve head, it did not affect mean arterial blood pressure at the doses that affected optic nerve head circulation, unlike nilvadipine. The plasma concentration of lomerizine (free base) obtained from rabbits at 15 min after administration at a dose of 0. 03 mg kg(-1)i.v., when time there was a significant increase in tissue blood velocity in the optic nerve head, was very similar to plasma concentration with healthy subjects receiving lomerizine at 10 mg (5 mgx2) day(-1), p.o., a dose that achieved a significant reduction in the frequency and mean duration of headache attacks but did not affect the blood pressure or heart rate. These results suggest that lomerizine may be clinically effective in favorably affecting the optic nerve circulation without producing systemic effects such as the hypotension seen during treatment with other Ca(2+)channel blockers.