138

Letters to the Editors

Br. J. clin. Pharmac. (1991),32

The lateral decubitus position may affect gastric emptying through an autonomic mechanism: the skin pressure-vegetative reflex The rate of gastric emptying is the principal factor and one of the most important rate limiting steps affecting the absorption of orally administered drugs (Levine, 1970; Nimmo, 1976; Prescott, 1974a, b). Posture is known to influence gastric emptying and may alter significantly the oral bioavailability of drugs. As compared with the left lateral decubitus position which retards gastric emptying and thereby drug absorption, the right lateral decubitus position greatly increases the rate of gastric emptying (Burn-Murdoch et al., 1980; Nimmo & Prescott, 1978). Positioning of the patient may prove to be a simple method of enhancing or retarding drug absorption in appropriate clinical situations (Rommel et al., 1978). However, the mechanism underlying this phenomenon is basically unexplained. We suggest that since gastric emptying is mediated by increased vagal tone (Carr & Brooks, 1978), the proposed mechanism could be due to the skin pressure-vegetative reflex (Takagi, 1957; Takagi & Kobayasi, 1955). Indeed, skin pressure produces substantial effects on various body functions such as autonomic functions, muscle tone, involuntary movements, and consciousness (Kosaka et al., 1967; Kumazawa, 1963; Nakayama, 1957; Ogawa et al., 1979; Takagi, 1957; Takagi & Kobayasi, 1955).

The phenomenon of different physiological effects in right vs left lateral decubitus position during surgery is also well known (Eggers et al., 1963; Lange et al., 1988; Mills et al., 1976; Norton & Conforti, 1984; Stein, 1952; Zack et al., 1974). Since our group has very recently demonstrated that asymmetrical pressure on the shoulder, thorax and buttocks can affect autonomic tone as measured by spectral analysis of R-R intervals of the electrocardiogram with pressure on the right side increasing vagal tone and pressure on the left increasing sympathetic tone (Backon, 1990, 1991; Backon & Kullok, 1990), we suggest that the phenomenon may be understood in terms of this reflex.

JOSHUA BACKON' & AMNON HOFFMAN2 'Mount Pleasant Hospital, Addiction Studies Foundation, P. O. Box 16336, Jerusalem and 2School of Pharmacy, Hebrew University, P.O. Box 12065, Jerusalem, Israel 91120 Received 11 September 1990, accepted 7 March 1991 AD ON I S 030652519100157E

References Backon, J. (1990). Forced unilateral nostril breathing: A technique that affects brain hemisphericity and autonomic activity. Brain Cogn., 12, 155-157. Backon, J. (1991). The right lateral decubitus position via the skin pressure-vegetative reflex may prevent anxiety, adverse autonomic reactions, and syncope in blood donors. Vox Sanguinis, (in press). Backon, J. & Kullok, S. (1990). Why asthmatic patients should not sleep in the right lateral decubitus position. Br. J. clin. Pract., 44, 448-449. Burn-Murdoch, R., Fisher, M. A. & Hunt, J. N. (1980). Does lying on the right side increase the rate of gastric emptying? J. Physiol., 302, 395-398. Carr, D. H. & Brooks, F. P. (1978). Vagally induced gastric antral contractions and gastric emptying of a liquid test meal. Quart. J. exp. Physiol., 63, 49-58. Eggers, G. W. N., deGroot, W. J., Tanner, C. R. & Leonard, J. J. (1963). Hemodynamic changes associated with various surgical positions. J. Am. med. Ass., 185, 1-5. Kosaka, M., Takagi, K. & Koyama, M. (1967). Reflex inhibition of cold shivering by pressure in the skin and the histological investigation of its afferent spinal pathway. Experientia, 23, 453-455.

Kumazawa, T. (1963). 'Deactivation' of the rabbit's brain by pressure application to the skin. EEG clin. Neurophysiol., 15, 660-671. Lange, R. A., Katz, J., McBride, W., Moore Jr., D. M. & Jillis, L. D. (1988). Effects of supine and lateral positions on cardiac output and intracardiac pressures. Am. J. Cardiol., 62, 330-333. Levine, R. R. (1970). Factors affecting the gastrointestinal absorption of drugs. Am. J. Dig. Dis., 15, 171-188. Mills, R. M., Mudge, G. H. & Lesch, M. (1976). Coronary sinus blood flow in trepopneic angina: Case report. Ann. Int. Med., 84, 295-296. Nakayama, T. (1957). Behaviour of cervical muscles in labyrinthine and skin-pressure reflexes. Jpn. J. Physiol., 7, 99-112. Nimmo, W. S. (1976). Drugs, diseases and altered gastric emptying. Clin. Pharmacokin., 1, 189-203. Nimmo, W. S. & Prescott, F. (1978). The influence of posture on paracetamol absorption. Br. J. clin. Pharmac., 5, 348-349. Norton, L. C. & Conforti, C. G. (1984). The effects of body position on oxygenation. Heart Lung, 14, 45-51. Ogawa, T., Asayama, M., Ito, M. & Yoshida, K. (1979).

Br. J. clin. Pharmac. (1991), 32 Significance of skin pressure in body heat balance. Jpn. J. Physiol., 29, 805-816. Prescott, L. F. (1974a). Gastrointestinal absorption of drugs. Med. clin. North Am., 58, 907-916. Prescott, L. F. (1974b). Gastric emptying and drug absorption. Br. J. clin. Pharmac., 1, 189-190. Rommel, A. J., Vukovich, R. A., Knill, J. R. & Sugerman, A. A. (1978). Posture-induced alterations in oral cephradine absorption kinetics. Clin. Pharmac. Ther., 23, 127. Stein, P. (1952). Tendency toward hypotension in left lateral

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recumbency. Arch. Int. Med., 10, 234-242. Takagi, K. (1957). Uber den Einfluss des mechanischen Hautdruckes auf die vegetativen Funktionen. Acta Neurovegetativa, 16, 439-447. Takagi, K. & Kobayasi, S. (1955). Skin pressure-vegetative reflex. Acta med. Biol., 4, 3-57. Zack, M. B., Pontoppidan, H. & Kazemi, H. (1974). The effect of lateral positions on gas exchange in pulmonary disease. Am. Rev. resp. Dis., 110, 49-55.

The lateral decubitus position may affect gastric emptying through an autonomic mechanism: the skin pressure-vegetative reflex.

138 Letters to the Editors Br. J. clin. Pharmac. (1991),32 The lateral decubitus position may affect gastric emptying through an autonomic mechanis...
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