The dizzy patient. Symptomatic treatment of vertigo

Stimulation of the semicircular canals via the rotary chair as a means to test pharmacologic countermeasures for space motion sickness

OBJECTIVE

Space motion sickness is currently treated pharmacologically with the empiric use of the H1 antihistamine promethazine, but use of this intervention is limited by the side effect of significant sedation. This creates a dilemma, as full cognition is particularly important during the same conditions likely to exacerbate the symptoms of space motion sickness. Using overstimulation of the semicircular canals with a rotary chair as a paradigm for space motion sickness, we evaluated four medications, commonly used for the treatment of terrestrial motion sickness and vertigo, for their efficacy in alleviating the simulated symptoms of space motion sickness.

STUDY DESIGN

Randomized, prospective, double-blind study.

SETTING

Tertiary referral center.

PATIENTS

Healthy male and female volunteers, 18 years of age or older, without history of neurologic or psychiatric disorders, and with no known allergies or any previous adverse reactions to the drugs used.

INTERVENTIONS

Lorazepam 1 mg, meclizine 25 mg, promethazine 25 mg, scopolamine 0.4 mg, or placebo.

MAIN OUTCOME MEASURE

The ability of each treatment to control the nausea and vomiting associated with our paradigm for space motion sickness was evaluated by measuring time of rotation pre- and posttreatment and time of symptom onset pre-and posttreatment.

RESULTS

Only scopolamine effected a mean change in duration of rotation that reached statistical significance when compared with placebo (p <0.008), with a greater than 40% increase in rotation time. Results with promethazine were not statistically significant.

CONCLUSION

Results showed a rank order of efficacy of scopolamine > promethazine > placebo > meclizine > lorazepam. Scopolamine significantly increased rotation time, but none of the treatments resulted in a significant delay to onset of symptoms.

Effects of drug countermeasures for space motion sickness on working memory in humans

Space motion sickness (SMS) is a problem during the first 72 h of space flight and during transitions from different gravity environments. There currently are no effective drug countermeasures for SMS that also accommodate the retention of optimal cognitive function. This creates a dilemma for astronauts because cognitive skills are particularly important during gravity transitions (e.g., take-off and landing). To quantify the cognitive side effects of potential drug countermeasures, an automated delayed matching-to-sample (DMTS) procedure was used to assess visual working memory before and after drug countermeasures (meclizine 25 mg, scopolamine 0.4 mg, promethazine 25 mg, or lorazepam 1 mg, given orally approximately 45 min prior to testing) and/or the induction of SMS by vestibular stimulation in a rotary chair (spinning). Sixty-seven normal healthy volunteers (mean age, in years, 26.6+/-4.8 S.D.; 24 females and 43 males) each participated in two test sessions, one 'off' drug and one 'on' drug. Spinning by itself significantly decreased task accuracy (Acc) and choice response speed, especially at longer recall delays. Meclizine alone had no effect on Acc or speed with or without spinning. Scopolamine alone decreased Acc, and with spinning, slowed speed. Promethazine alone had no adverse effect, but combined with spinning, decreased Acc and speed. Lorazepam alone decreased speed, and with spinning, decreased Acc. The data suggest that, at clinically useful doses, the rank order of the drugs with the best cognitive profiles is meclizine>scopolamine>promethazine>lorazepam.

Menière's disease: pathophysiology and treatment

Menière's disease is defined by the association of 4 symptoms: vertigo attacks, fluctuating hearing loss, tinnitus and an auricular plenitude sensation. The pathophysiology is commonly explained by a distension of membranous labyrinth by the endolymph, equally called endolymphatic hydrops. Recent studies also tend to relate the disease to immune mechanisms. The treatment is medical in the majority of patients but there is no international consensus on the management of the different stages of Menière's disease. Regarding the lack of clinical studies clearly demonstrating the effectiveness of a certain therapy or another. the recommendations are usually based on the empirical experience of practitioners and on the observation of a marked amelioration at 2 years of treatment in the majority of patients. The treatment of the acute phase of Menière's disease is basically symptomatic. Vestibular suppressant drugs have a well-established record in controlling acute attacks of vertigo. Most have variable anticholinergic, anti-emetic and vestibular sedative effects. If necessary, the administration of benzodiazepines will help to alleviate anxiety. Long term management of Menière's disease includes a low salt diet, the use of diuretics in the post-crisis phase, and the very common use in Europe of histaminergic agents. Corticosteroids are used in bilateral forms of Menière's disease, particularly if an autoimmune basis is suspected. All authors insist on the interest and the importance of regular follow-up, especially with regard to the psychological status and responsiveness to treatment of the patient. Surgical indications are rare and the least invasive procedures are used first. The choice of the procedure should take into consideration the need to preserve the auditory function of the patient.

Autoradiography in brain of Macaca fascicularis monkeys after injection of acetyl-DL-leucine [2-14C] (Tanganil)

Acetyl-DL-leucine [2-14C]: Tanganil a antivertigal drug has been injected intravenously in two macaca monkeys which have been sacrificed 2 and 5 minutes later. Radioactivity distribution has been studied by autoradiography in the brain. An important uptake of radioactivity is localized in the cortical structures and in several tisses such as nuclei of the vestibular system, including the inner ear.

Pharmacological treatment of vertigo

A review of the treatment of vestibular disorders with drugs is presented. In animal experiments, administration of certain drugs, e.g. alcohol, barbiturates and chlorpromazine, retards the vestibular compensation, while others, e.g. caffeine, amphetamine and ACTH, accelerate the compensation. In compensated animals, some drugs produce overcompensation and some decompensation. A double-blind, randomized trial of the effect of scopolamine and dimenhydrinate in patients with vertigo of varying origin showed, as compared with placebo, that these drugs did not significantly alleviate the vestibular imbalance. The reason for the poor efficacy of the treatment may have been overcompensation of vestibular function loss and adverse effects caused by the drugs. Care should be taken that the drugs used do not retard the vestibular compensation caused by the central nervous system.

Effect of drug therapy on compensation from vestibular injury

The influence of selected drugs on compensation from unilateral labyrinthectomy was studied in the cat. The drugs investigated included: a. amphetamine, b. diazepam, c. dimenhydrinate, d. scopolamine, and e. trimethobenzamide. The most beneficial drugs for improving recovery were a stimulant (amphetamine) and a general anti-emetic (trimethobenzamide). It is postulated they had this effect by improving the overall activity level with general exercise being a known positive influence. Conversely the other drugs either had little effect on recovery or hindered it, by presumably suppressing the sensory imbalance in the vestibular system that is essential stimulus to ultimate recovery.

Vertigo. Current concepts in management

Vertigo is not a disease, but a symptom. The management of vertigo requires more than the treatment of the symptom alone, as it concerns the whole physical and psychological condition of the patient. In addition to causal treatment, symptomatic treatment is needed in many cases. This specific treatment consists of vestibular exercises and drug therapy. The efficacy and use of the different drugs available are discussed.