Corticosteroids in The Treatment of Acute Low Back Pain

Oral steroids have been found effective in the treatment of inflammatory reactions associated with allergic states, rheumatic and autoimmune diseases, and respiratory disorders. Corticosteroids interact with receptor proteins in target tissues to regulate gene expression and ultimately protein synthesis by the target tissue. As these interactions and regulatory processes occur slowly, most of the effects of corticosteroids are not immediate and become apparent hours following their introduction. Recent investigations have suggested an additional and more immediate component to corticosteroid action mediated by an interaction with membrane-bound protein receptors.

Over the past two decades, the biochemical contributions to sciatica and low back pain have been the focus of much attention. In the late 1970's the nuclear material of the vertebral disc was found to be antigenic and capable of producing an in vitro autoimmune reaction. It was hypothesized that a chemical radiculitis might explain radicular pain in the absence of a more mechanical stressor.

Phospholipase A2 (PLA2), a potent inflammatory mediator, has demonstrated to be released by discs following injury. The anti-inflammatory and immunosuppressive effects of glucocorticoids are largely secondary to their inhibition of the immune responses of lymphocytes, macrophages, and fibroblasts. Whereas NSAIDs principally inhibit prostaglandin synthesis, corticosteroids interfere earlier in the inflammatory cascade by inhibiting PLA2 actions and thereby curtailing both the leukotriene and prostaglandin mediated inflammatory response.

Studies: Steroids and Acute Low Back Pain
Studies designed to investigate the use of oral steroids in the setting of acute low back pain are limited. In 1986, Haimovic and Beresford compared oral dexamethasone (Decadron®) with placebo in the treatment of 33 patients with lumbosacral radicular pain. Subjects receiving dexamethasone were given a tapering dose, from 64- to 8-mg over seven days. Early improvements (within seven days) were not significantly different between the two groups, occurring in seven of 21 patients in the dexamethasone group and four of 12 in the placebo group.

In those subjects initially found to have radicular type pain on straight leg-raising, however, eight of 19 treated with dexamethasone, compared with only one of six in the placebo group, had diminished pain on straight leg raising repeated within seven days. The limitations of this study include a small subject number, the use of additional analgesics, which may have obscured group differences, the clinical uncertainty of a radicular process in a significant number of subjects, and the loss of several patients to follow up after one year.

Adverse Effects
In the setting of acute low back pain with radiculopathy, oral corticosteroids are typically prescribed in a quick tapering fashion over one week. Multiple adverse effects have been associated with prolonged steroid use, including suppression of the hypothalamic-pituitary-adrenal axis, immunosuppression, psuedotumor cerebri and psychoses, cataracts and increased intraocular pressure, osteoporosis, aseptic necrosis, gastric ulcers, fluid and electrolyte disturbances and hypertension, and impaired wound healing.

The severity of these complications correlates with the dosage, duration of use, and the potency of the steroid prescribed. While the incidence of steroid-induced myopathy does not appear to be directly related to the dosage of steroid prescribed nor the duration of use, it appears to be more prevalent with the use of steroids containing a 9-alpha fluorine configuration, such as triamcinolone (Aristocort®). The relationship between hypertensive side effects and the duration of therapy is also not very clear; steroids should be prescribed with greater caution in the elderly, in those individuals with known hypertension, and when compounds with greater mineralocorticoid properties are prescribed. As hyperglycemia is a well-known complication of corticosteroid use, oral steroids should be prescribed with caution in the diabetic population.

As potent anti-inflammatory agents, oral steroids represent a theoretically useful agent in the treatment of patients with radiculopathy due to local inflammation secondary to disc injury or herniation. While many adverse effects are associated with oral steroid use, these are more frequently encountered in the setting of prolonged administration. The effectiveness of oral steroids in the acute low back pain population remains unproven; further research in this area is needed.

Reference:
Malanga GA, et al. Pharmacologic Treatment of Low Back Pain. In Physical Medicine and Rehabilitation State of the Art Reviews, Philadelphia, Hanley and Belfus Vol.13, No.3, October, 1999