Paula Viñas
José de Felippe Junior

A náusea (do grego nausia, vontade de vomitar), é uma ânsia acompanhada ou não de vômito. O vômito é um ato reflexo que expulsa violentamente o conteúdo gástrico. Simultaneamente com a angústia nauseosa o vômito pode provocar sintomas como palidez, suor frio, bradicardia e impressão de debilidade ou desmaio próximo.

Mecanismo de Ação: impulsos nervosos através do nervo vago (sistema nervoso parasimpático) chegam ao sistema nervoso central, no centro do vômito (tecido reticular lateral do bulbo). Este coordena o ato motor periférico que efetua o vômito, relaxando a cardia e os músculos faríngeos , contraindo as paredes abdominais e o diafragma e expulsando o conteúdo gástrico.

Os antieméticos podem agir por diferentes vias no mecanismo do vômito:

1-através do estômago

2-pelos nervos vegetativos aferentes

3-através dos quimioreceptores do IV ventrículo (estimulados pela apomorfina, infecções, necrose e outros agentes químicos tóxicos)

4-labirinto e cerebelo

5-córtex cerebral e psiquismo

As náuseas e vômitos são despertados por uma gama muito grande de estímulos sensitivos:

1. Nas lesões intracraniais e na enxaqueca pode ocorrer uma distensão das estruturas craniais por uma hipertensão cérebro-meníngea ou mudanças vasomotoras angio-cerebrais.
2. estímulos visuais e olfativos desagradáveis (cheiros e visões enjoativos, nojo)
3. sabores desagradáveis ou irritantes à área gustativa
4. estimulação contínua e asincrônica do aparelho vestibular (enjôo de viagens)
5. distensões ou irritações que através do sistema vegetativo vagal estimulam o ato do vômito
6. dor física violenta
7. toxinas exógenas: digitálicos, opiáceos, apomorfina
8. toxinas endógenas: uréia, necrose com ou sem inflamação

Plantas com efeitos nas náuseas e vômitos

Gengibre

Os trabalhos científicos a seguir demostram a eficiência do gengibre nas náuseas e vômitos. Foram realizados experimentos em náuseas pós operatórias, cadetes desacostumados com viagens em alto mar e pessoas susceptíveis a náuseas colocadas em cadeiras mecânicas. Todos os experimentos demonstraram que a raíz do gengibre reduz os sintomas de náuseas e vômitos.

A raíz do gengibre parece também exercer ações anticolinérgica e antihistamínica.

Experimental Double– Blind Study: 60 women who had major gynecological surgery randomly received ginger root, metoclopramide or placebo. There where statistically significantly fewer incidences of nausea in the group that received ginger compared to placebo (p<0,05). The number of incidences of nausea in the group that received either ginger root or metoclopramide were similar. Also, the administration of an antiemetic after surgery was significantly more frequent in the placebo group as compared to the other 2 groups. (p<0,05) (Bone ME, Wilkinson DJ, Young JR, et al. Ginger root – a new antiemetic. The effect of ginger root on postoperative nausea and vomiting after major gynaecological surgery. Anaesthesia 45(8):669-71, 1990)

Experimental Double Blind Study : 80 naval cadets unaccustomed to sailing in heavy seas were studied during voyages on the high seas. Each randomly received either 1 gr of powered ginger root or a placebo and symptons of seasickness were recorded each hour for 4 hours. Ginger was significantly better than placebo in reducing the frequency of vomiting (72% reduction) and cold sweats (p<0,05). Cadets receiving ginger also indicated a reduction in nausea and vertigo compared to controls; however, the reduction failed to reach statistical significance. Overall, symptons were 38% less in the ginger group, than in the controls (Grontved A et al. Ginger root against seasickness. A controlled trial on the open sea Acta Otolaryngol 105 (1-2):45-9,1988)

Experimental Double – Blind Study : 18 male and 18 female volunteers who had previously indicated an extreme susceptility to motion sickness were randomly divided into 3 groups. The first group received a placebo, the second 100 mg dimenhydrinate, and the third 940 mg of powdered ginger root 25 min. before testing. The subjects were than blindfolded, led to a concealed mechanical chair, spun around, and asked to report their feelings of nausea every 15 seconds while they performed mental tasks. The test was stopped when either the subject vomited or asked that it be stopped. Subjects who received ginger remained in the chair an ave. of 5,5 min., compared with an ave. of 3,5 min. for the dimenhydrinate gp. and 1,5 min. for the placebo group.

Once nausea began, however, sensations of nausea and vomiting progressed at the same rate in all groups. More than 90% of pts. with motion sichness who took 2-4 caps of ginger root prior to travelling, and took 2 more approximately every hour or whenever they felt slightly nauseated, reported excellent results. Ginger root was found to be equally effective for automobile, airplane, train or boat trips. It is hypothesized that, unlike dimenhydrinate that works on the central nervous system, ginger affects the gastrointestinal tract and slows the feedback interaction between the stomach and the nausea center in the brain by absorving and neutralizing GI toxins and acids (Mowrey DB, Clayson DE. Motion sickness, ginger, and psychophysics. Lancet i:655-7, 1982)

The efficacy of ginger root appears to be due to anticholinergic and antihistaminic actions.

Animal Experimental Studies : Results of studies with rabbits, isolated rat fundus strip preparations and guinea-pig isolated ileum suggest that the pungent constituents of ginger release substance P from sensory fibers which either stimulates cholinergic and histaminic neurons to release acetylcholine and histamine, respectively, or produces direct smooth muscle contraction by activating M and H1 receptors correspondingly. It is proposed that after being excited by substance P, M and H1 receptors are inactive temporarily and unable to be excited by agonists; therefore ginger juice exhibits anticholinergic and antihistamine actions (Qian DS, Liu ZS. Pharmacologic studies of antimotion sickness actions of ginger. Chung Kuo Chung Hsi I Chieh Ho Tsa Chih 12(2):95-8,70,1992) (in Chinese)

Experimental Double-Blind Study: In order to determine whether the nystagmus response to optokinetic or vestibular stimuli might be altered by some agent in powdered ginger root, normal subjects were examined after administration of ginger root, dimenhydrinate and placebo. Eye movements were recorded using standart EMG equipment and evaluation was performed by automatic nystagmus analysis. Ginger root had no effect on experimentally – induced nystagmus, while dimenhydrinate caused a reduction in the nystagmus response to caloric, rotatory and optokinetic stimuli. Results suggest that neither the vestibular nor the oculomotor system are influenced by ginger, and thus a central nervous system mechanism, which is characterist of conventional anti – motion sickness drugs, can be excluded. It is likely that any reduction of motion – sickness symptons derives from the influence of ginger root agents on the gastric system (Holtmann S, Clarke AH, Scherer H, Hohn M. The anti – motion sickness mechanism of ginger. A comparative study with placebo and dimenhydrinate. Acta Otolaryngol (Stockh)108(3-4):168-74, 1989)

Experimental Double – Blind Crossover Study: 18 healthy volunteers received either 1gr of ginger root or a lactose placebo 1hr. prior to caloric stimulation of the vestibular system. Compared to controls, ginger root failed to affect nystagmus as measured by electronystagmograms (Grontved A, Hentzer E. Vertigo – reducing effect of ginger root. A controlled clinical study. ORL J Otorhinolaryngol Relat Spec 48(5):282-6, 1986)

Ginger: history and use.

Adv Ther;15(1):25-44, 1998 Jan-Feb. Langner E; Greifenberg S; Gruenwald J

Phytopharm Consulting, Berlin, Germany

Resumo: Ginger is well known in the form of ginger sticks or ginger ale. If these are consumed during travel, the traveler imbibes, albeit subconsciously, a healing plant for motion sickness. The efficacy of ginger rhizome for the prevention of nausea, dizziness, and vomiting as symptoms of motion sickness (kinetosis), as well as for postoperative vomiting and vomiting of pregnancy, has been well documented and proved beyond doubt in numerous high-quality clinical studies. The use of this ancient medicine for gastrointestinal problems (stimulation of digestion) has been given scientific approval. Today, medicinal ginger is used mainly for prevention of the symptoms of travel sickness.