Chronic pain

Remember that most people who try a painkiller will get little benefit from it, but a few will improve quite a bit. When a drug works it’s typically helpful within 2 – 4 wks, so painkillers should be reassessed then & stopped if not working. A person can respond to one drug within a class but not another, so it’s worth trying different ones.

OPIAD is a syndrome called opioid-induced androgen deficiency. In men this may manifest as erectile dysfunction and loss of muscle mass; in women as oligomenorrhoea or amenorrhoea. In both sexes it can cause loss of libido and reduced fertility; depression, anxiety, and low energy; flushing and sweating; and osteoporosis/fractures. It can be tested for by checking testosterone and FSH/LH levels (all will be low, as the suppression occurs centrally as well as directly on the testes.) Prevalence is surprisingly high – between 21 and 86% of patients on long-term opioids.

Carbamazepine is the initial choice of treatment for trigeminal neuralgia (NICE). For other types of neuropathic pain, the NICE-recommended options are amitriptyline, duloxetine, gabapentin, or pregabalin, with no particular batting order – assess at 2 – 4 weeks, titrate if necessary, and try different choices from the four if the first choice is ineffective. Tramadol should only be used as acute rescue therapy. Capsaicin is a possibility for patients with localised neuropathic pain who do not wish to take oral treatment.

SIGN suggests topical lidocaine as a second-line choice for post-herpetic neuralgia.

  • Amitriptyline – take 2 hours before bedtime, can be titrated up to 125 mg (the starting dose is 10 – 25 mg, which is what I’d already use).
  • Gabapentin – start with 300 mg nocte or 100 mg nocte in elderly, and titrate up to 1200 mg.
  • Duloxetine – start with 60 mg od or 30 mg in elderly, titrate up to 60 or 120 mg
  • Pregabalin – start with 75 mg nocte or 25 mg in elderly, titrate up to 300 – 600 mg daily

Although paracetamol has been linked with an increase in several adverse events in observational studies (cardiovascular, GI, renal), SIGN feels this may be due to confounders and the benefits may outweigh the harms. Faint praise, but I suppose we don’t have much in the way of other low-risk pharmaceutical options.

Night pain is not helpful as a red flag for cancer in assessing spinal pain. A past history of cancer is the only helpful red flags. Red flags are also more like pale pink flags in practice, it seems – about 80% of patients with acute low back pain have at least one, and referring all patients for imaging would lead to massive rates of unnecessary investigation, so considering the overall probability of serious disease is a more beneficial approach.

 

(Pulse on-line learning module – Hot Topics in Non-Palliative Pain Control)

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About Dr Sarah

I'm a GP with a husband and two young children.
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