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Treating Exacerbations of Chronic Pain

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Exacerbations of chronic pain may cause patients to present to the emergency department with acute episodes, commonly of back or abdominal pain.

Of course, there may also be acute conditions, which occur that are unrelated to the chronic condition, or post-operative analgesia is required.

In this situation, the usual medication is insufficient to provide analgesia but will interact with any treatment given for the acute condition.

If the patient is on opiate medication, they will have developed tolerance to the effect not only of the medications they are taking, but also a degree of cross-tolerance to the effect of other opioid drugs.

This cannot necessarily be accurately predicted, as it will vary between individuals. It is not within the scope of this article to address the complexities of prescribing under these conditions.

However, it is worth noting Mehl-Madrona's study published last year ([i]).

This looked at use of a combination of keterolac and chlorpromazine to replace the more usual meperidine/promethazine combination in the emergency room for exacerbations of chronic pain.

Keterolac is a potent Non-steroidal anti-inflammatory drug (NSAID) that is indicated for moderate to severe pain (NOT mild pain), chlorpromazine is a neuroleptic see above).

Meperidine (pethidine) is a short-acting opiate given intramuscularly and promazine is given to prevent nausea and vomiting which may be induced by meperidine.

Patients were given either intramuscular doses of 60mg keterolac +50-75 mg chlorpromazine (KET-CHLOR)  (depending on weight) or 50mg meperidine plus 25-50mg promethazine (MEP-PROM). (Heavier patients were given 1.5 doses).

It was found that the pain relief of the 2 different protocols was comparable, but the KET-CHLOR patients had fewer side effects and this combination worked better for nausea (chlorpromazine is a more potent antiemetic than promazine).

Although the author did not refer specifically to the problems of previous tolerance, the study suggests that using a NSAID may be sufficiently effective to negate the need to use extra opiate medication in addition to the patient's usual regime.      

Dr. Sarah Andreae-Jones MB BS
Patron of ASG
July 2000.

[i] Mehl-Madrona LE J Am Board Fam Pract 1999;12(3):188-194 Comparison of keterolac-chlorpromazine with meperidine-promethazine for treatment of exacerbations of chronic pain.