Vitamin B6 therapy during childbearing years: cause for caution?

Vitamin B6, or pyridoxine, is either prescribed or recommended in large doses for a variety of ailments. These ailments include morning sickness and premenstrual syndrome, despite the fact that the effect of large doses of vitamin B6 on developing human fetuses is currently unknown. Both clinical reports and recent experimental evidence indicate, however, that large doses of vitamin B6 can have adverse affects on proprioceptive neuron function, and these deficits may be permanent if caused during development. This evidence suggests that ingestion of large quantities of vitamin B6 should be viewed with caution by pregnant women and women of childbearing potential.

Automatic postural responses are delayed by pyridoxine-induced somatosensory loss.

Pyridoxine given in large doses is thought to destroy selectively the large-diameter peripheral sensory nerve fibers, leaving motor fibers intact. This study examined the effects of pyridoxine-induced somatosensory loss on automatic postural responses to sudden displacements of the support surface in the standing cat. Two cats were trained to stand on four force plates mounted on a movable platform. They were given pyridoxine (350 mg/kg, i.p.) on 2 successive days (0 and 1). Electromyographic (EMG) activity was recorded from selected hindlimb muscles during linear ramp-and-hold platform displacements in each of 12 directions at 15 cm/sec. In control trials onset latencies of evoked activity in hindlimb flexor and extensor muscles ranged from 40 to 65 msec after the onset of platform acceleration. After injection the EMG latencies increased over days, becoming two to three times longer than controls by day 7. Excursions of the body center of mass (CoM) in the direction opposite to that of platform translation were significantly greater at day 7 compared with controls, and the time at which the CoM subsequently reversed direction was delayed. Both animals were ataxic from day 2 onward. Histological analysis of cutaneous and muscle nerves in the hindlimb revealed a significant loss of fibers in the group I range. Our results suggest that large afferent fibers are critical for the timing of automatic postural responses to ensure coordinated control of the body CoM and balance after unexpected disturbances of the support surface.

Articaine hydrochloride: a study of the safety of a new amide local anesthetic.

BACKGROUND: Articaine is an amide local anesthetic introduced clinically in Germany in 1976 and subsequently throughout Europe, Canada and, in 2000, the United States. METHODS: The authors report on three identical single-dose, randomized, double-blind, parallel-group, active-controlled multicenter studies that were conducted to compare the safety and efficacy of articaine (4 percent with epinephrine 1:100,000) with that of lidocaine (2 percent with epinephrine 1:100,000). RESULTS: A total of 1,325 subjects participated in these studies, 882 of whom received articaine 4 percent with epinephrine 1:100,000 and 443 of whom received lidocaine 2 percent with epinephrine 1:100,000. The overall incidence of adverse events in the combined studies was 22 percent for the articaine group and 20 percent for the lidocaine group. The most frequently reported adverse events in the articaine group, excluding postprocedural dental pain, were headache (4 percent), facial edema, infection, gingivitis and paresthesia (1 percent each). The incidence of these events was similar to that reported for subjects who received lidocaine. The adverse events most frequently reported as related to articaine use were paresthesia (0.9 percent), hypesthesia (0.7 percent), headache (0.55 percent), infection (0.45 percent), and rash and pain (0.3 percent each). CONCLUSIONS: Articaine is a well-tolerated, safe and effective local anesthetic for use in clinical dentistry.