Many pains are controlled by non-addictive procedures ranging from exercise to a variety of
analgesic medications. Some pains are controlled by
analgesic drugs, but at the cost of intolerable side effects. This is true both for non-steroidal anti-inflammatory drugs and
opioids. The worst pains are most often controlled by
opioids, but problems of tolerance and addiction limit these successes. This contribution provides a statement on non-addictive, non-
opioid drugs which help to control
pain. Just as these vary in their success, so they vary also in the strength of the scientific evidence which supports their use. The groups of drugs to be considered can be evaluated in three respects; evidence of
analgesic effect in controlled trials; evidence of side-effects compared with control substances and with standard experience; evidence of usefulness in clinical practice. The latter which is the most important for practice often has the least scientific proof. Six main classes of drugs are recognized which provide
analgesic effects, other than
opioids. 1) Non-steroidal anti-inflammatory drugs are widely accepted as
analgesics on the basis of animal studies, numerous controlled investigations and clinical practice. Acetaminophene may not be anti-inflammatory, but is recognized as an effective
analgesic which in many other respects resembles the above. 2) Muscle relaxants, e.g.
cyclobenzaprine or
baclofen have varied actions, but often provide some relief of
pain. 3)
Antidepressants may be
analgesic if they relieve depression which is giving rise to
pain. This applies to all anti-depressants. Some
antidepressants have been shown to be
analgesic in the absence of depression. The best accredited of these is
amitriptyline.
Antidepressants too have significant side effects. A serotoninergic hypothesis is insufficient to explain the actions of
antidepressants in relieving
pain in the absence of depression. 4)
Phenothiazine neuroleptics (and possibly some others) may be
analgesic. Drugs reported to be
analgesic include
chlorpromazine,
fluphenazine,
perphenazine,
trifluoperazine,
methotrimeprazine (
levomepromazine) among others.
Haloperidol has also been utilized. Well controlled evidence exists with the use of
methotrimeprazine (
levomepromazine) used as an injection. The
analgesic effect of oral
neuroleptics is less well established and mostly depends upon clinical observation, withdrawal and re-challenge. 5)
Anticonvulsants. 6) Other drugs. Non-steroidal anti-inflammatory drugs and some muscle relaxants, e.g.
cyclobenzaprine are best used in the short term. The gastrointestinal side effects of non-steroidal anti-inflammatory drugs have been quite troublesome and over 2% of patients followed over five years are at risk of developing peptic ulceration from such medication.
Cyclobenzaprine is best used in short term treatment, but may be used intermittently for
chronic pain.
Antidepressants,
neuroleptics,
anticonvulsants and some other drugs can be used long term. Topical
analgesic agents may also be used.