Most fibromyalgia sufferers will at some stage be offered a prescription for one or more of the officially approved drugs – Lyrica, Cymbalta, and Savella.
Many will ask their doctors two important questions: How good are these drugs and what harm can they cause me?
Many would be surprised by the answers they get – if the doctor is willing and able to provide them.
The concepts of NNT/NNH
One way to assess the effectiveness of drugs for pain management is by looking at the Number Needed to Treat (NNT) value.
The NNT value for drugs used to treat specific painful conditions is derived from large clinical trials that record the number of patients who report 50% or more reduction in their pain, compared to results from a placebo. The lower the NNT, the better the drug.
For example, if 10 patients with a specific condition are prescribed a drug and only one of them reports relief of pain, the NNT value for that drug is 10. This means that the other 9 patients will find the drug to be ineffective.
Continuing on the same theme, the potential for drugs to cause harmful side effects is expressed by another value – the Number Needed to Harm (NNH).
The NNH values for the three fibromyalgia drugs gives us an indication of how many patients need to be treated before one of them will report a harmful side effect. The higher the NNH, the safer the drug is.
By the way, it is well known that people taking placebo drugs can report adverse events.
NNT for Fibromyalgia Drugs
This means that only one out of 10 patients taking Lyrica (Preglabin) will have pain relief of 50% or more. Only one out of 6 taking Cymbalta (Duloxetine) will have relief of pain and only about one out of 8 taking Savella (Milnacipran).
NNH for Fibromyalgia Drugs
The overall values for side effects of each drug, when compared to placebo, and expressed as NNH are as follows: between 6 -18 for Cymbalta; between 7-14 for Savella 7-14; and around 6 for Lyrica.
This means for every 6 patients with fibromyalgia treated with Lyrica, one of them will report a harmful side effect. There is a wide range of NNH’s for both Cymbalta and Savella.
Some adverse effects are relatively minor and will not deter a person from taking an effective drug. Other adverse effects are more serious and can be a reason for discontinuing the drug.
In the case of Lyrica, randomized controlled trials have shown that doses of 600 mg daily produce drowsiness in 15-20% and dizziness in 27% to 46%.
Other side effects include dry mouth, weight gain, peripheral oedema (swelling). In another important review, it was found that treatment was discontinued due to adverse events in one out of 4 patients.
In summary, a minority of patients will report substantial benefit with Lyrica, and more will have moderate benefit. Many will have no or trivial benefit, or will discontinue the drug because of adverse events.
Is this the sort of information that patients would like to have given to them?
In my experience, the answer is a resounding YES. But as each person is a unique individual, it is impossible to accurately predict who will and who will not like a particular drug.
“Doctors are men who prescribe medicines of which they know little, to cure diseases of which they know less, in human beings of whom they know nothing.”
These oft-quoted words by the French philosopher Voltaire [1694-1778] still have a ring of truth about them. We now know much more about the drugs we prescribe, and about the various diseases we have uncovered and classified. But we still have much to learn about the responses of individual human beings.
Those who have been awarded a diagnosis of fibromyalgia find themselves in a “double bind.”
On the one hand, the very diagnosis can arouse disbelief at all levels of society and, on the other hand, the available drugs afford most of them little, if any, relief of pain.
John Quintner, MD, is a rheumatologist and pain medicine specialist in Australia who recently retired from clinical practice.
He has published numerous articles on chronic pain in Pain Medicine, Clinical Journal of Pain, The Lancet and other medical journals.