Evidence for Opioid Rotation • 89
EQUIANALGESIC TABLES vidual characteristics, such as age, renal function, side
Equianalgesic tables can guide physicians to estimate the effects, and type of pain syndrome. It is important to
optimal dose for a patient of a new opioid that should realize that conversion ratios can differ according to the
replace the opioid to which the patient has started to patient population and the sensitivity of the underlying
develop tolerance. They provide only broad guidelines etiologies. Different pain syndromes, such as osteoar-
for selecting the dose of an opioid because of differences ticular diseases, neuropathic pain, or oncologic pain
between the populations studied to define the equivalent states, may demonstrate a variable and highly unpre-
dose, with those patients requiring opioid rotation. As dictable clinical response, which devaluates the impor-
stated above, there are large individual pharmacokinetic tance of conversion tables.44 Besides, in both chronic
and even larger pharmacodynamic differences in opioid noncancer and cancer patients, considerable inter-
pharmacology. individual differences exist in the pharmacokinetic
The calculations of equianalgesic doses often give the and pharmacodynamic behavior of different opioids,
highest dose for comparable analgesic effects. However, making an individual dose titration mandatory.22,39,45,46
these conversion tables have no scientific evidence.41
They are often based on results of older clinical trials SAFETY OF EQUIANALGESIC TABLES
that had the objective to compare the efficacy of two The majority of patients needs a lower dosing of the
opioids in a short time frame. Some of these trials new opioid than the dose theoretically calculated with
describe single medication administrations.42,43 The an equianalgesic table.43,47,48 Because of an incom-
treating physician should be well aware of the limita- plete cross-tolerance, it is recommended to reduce the
tions of equianalgesic tables. calculated dose by 33%. For safety reasons, the new
opioid will be initiated at the lowest dose that, if neces-
Ongoing diligent patient assessment is the most
sary, can be gradually increased to achieve adequate
important step in the equianalgesic conversion pro-
analgesia.35,43,45
cess. The conversion must take into account indi-
Reference works such as the Textbook of Pain
vidual patient characteristics such as age, renal
(Wall and Melzack, 5th edition)49 provide conversion
function, side effects and the patient’s pain syndrome.
tables whereby parenteral morphine 10 mg is used as
In addition, if the opioid dose is not adequate to
the unique comparator to calculate all other opioid
begin with, the conversion dose is less likely to be
doses in single patients. A recently published evidence-
effective. In all situations, once the patient is con-
based guideline for the management of cancer pain
verted, liberal titration and adjustment of individual-
offers a conversion table based on the literature50
ized doses for each patient are required to ensure that
(Table 2). Based on a retrospective cohort study in
the conversion transition is smooth and provides
patients with cancer and noncancer pain, the equipo-
the patient with the analgesia needed to adequately
tency ratio of transdermal buprenorphine to oral mor-
manage the pain.43
phine is established at 1:110 to 1:115.51 The available
So, the proposed opioid dose should be based on a conversion tables mainly report on the formulation(s)
theoretical dose calculation and titrated in accordance available in the country where the study is performed;
with the observed clinical efficacy and the patient’s indi- unfortunately, the formulations may differ from one
Table 2. Conversion Ratios for Opioid Rotation
Morphine Morphine Oxycodone Oxycodone Fentanyl Hydromorphone
Oral Subcutaneous/Intravenous Oral Subcutaneous/Intravenous Transdermal Oral
mg/24 hours mg/24 hours mg/24 hours mg/24 hours mcg/hours mg/24 hours
30 10 15 7.5 12 4
60 20 30 15 25 8
120 40 60 30 50 16
180 60 90 45 75 24
240 80 120 60 100 32
360 120 180 90 150 48
480 120 240 120 200 64
Buprenorphine was not included in the source guidelines. Mercadante32 identified a ratio of 70:1 for oral morphine : transdermal buprenorphine and 0.6:0.8 for transdermal
fentanyl : transdermal buprenorphine.
