Muscle relaxants may enhance the effect of analgesics

Muscle relaxants alone do not appear to be useful therapeutic agents in either ALBP or CLBP (Kuijpers et al. 2010). They are claimed, however, to be useful in combination with either NSAID in ALBP or with opioids in CLBP (Table 25.3). The culprit of the muscle relaxants is that they are heavily burdened with UDEs. The anticholinergic agents, as methocarbamol, orphenadrine, or tizanidine, go along with drowsiness, headaches, and typical anticholinergic effects, as increase of intraocular pressure, problems ofvoiding urine, and changes of the GI-tract motility. Alternatively, benzodiazepines, including diazepam and tetrazepam, may be used. They also increase sedation, tiredness, and drowsiness. They have no anticholinergic effects, but often induce drug abuse and drug dependency. Worldwide, there is a dramatic overuse of benzodiazepines in elderly people which gives rise to many fractures resulting of drowsiness and instability, particularly at night (Pariente et al. 2008).

Taken together, muscle relaxants may be used for short periods of time only. Benzodiazepines often induce abuse and cause fractures in elderly. In several European countries, flupirtine is used in ALBP. It is claimed to have a spasmolytic effect due to opening potassium channels. The effect of flupirtine in ALBP is not well documented (Li et al. 2008; Williams et al. 2010). Flupirtine should not be used in specific or CLBP as it may cause liver toxicity (Arzneimittelkommission der Deutschen Arzteschaft 2007).