Page 136 Guide to Pain Management in Low-Resource Settings

124 Katarina Jankovic

opioids only slightly better than placebo. Interest- respiratory depression in the neonate is the primary
ingly, midwifes have rated pethidine much better than reason for selecting a particular opioid. Regarding this
parturients, probably because sedation was confused potential, pethidine (meperidine) may be preferred over
with analgesia. others, as long as maximum daily doses (500 mg) are
respected. Pethidine remains the only opioid with dose-
Which route of administration dependent neurotoxicity. Th ere is no evidence in the
for systemic analgesia should be scientifi c literature that any other opioid is signifi cantly
more eff ective than pethidine. Also, pethidine is widely
preferred, and why? available and aff ordable. If available, nalbuphine, butor-

phanol, or tramadol may be also be used. Th ese opioids
If an anesthesiologist is not available, pethidine (me-
are not “pure” agonists of the mu-receptor, but mixed
peridine) is usually the drug of choice. It remains the
agonists and antagonists, which is the reason for their
best investigated and most often used opioid in labor.
unique safety regarding respiratory depression.
Th e dose of pethidine commonly prescribed is 1 mg/
However, as with other opioids, respiratory
kg i.m. up to the maximum dose of 150 mg/kg. Th e in-
depression may be avoided with pethidine. To achieve
tramuscular route is not recommended because it is
that outcome in the neonate, it is recommended to
not dependable—the rate of drug-absorption may vary.
observe a certain time corridor for the application of
Intravenous administration is more reliable, and the
pethidine to the parturient. Side eff ects are more like-
maximum total dose of 200 mg is reported to produce
ly to occur if delivery is between 1 and 4 hours after
signifi cantly lower pain scores and no diff erence in ma-
administration of pethidine. As a result, the classic
ternal or neonatal complications. Higher doses have to
teaching is that the neonate should be delivered within
be strictly avoided, since pethidine may provoke sei-
1 hour or more than 4 hours after the last pethidine
zures. Th is is due to the drug’s unique pharmacological
application. Timing of delivery, however, is diffi cult
structure, which gives it a special place among the opi-
to predict with precision. In addition, the metabolite
oids.
norpethidine is pharmacologically active, with a pro-
longed half-life in the neonate of up to 2½ days. Th us,
What is the clinical relevance neonatal behavior might be aff ected, and diffi culties
of opioids passing with breastfeeding are possible, regardless of the tim-
the placenta barrier? ing of maternal administration.
Pentazocine should not be used because of its
Opioids cross the placenta and may aff ect the fetus. Th is potential to cause dysphoria and sympathetic stimula-
is manifested in utero by changes in fetal heart rate pat- tion. Th eoretically, the opioid best suited for providing
terns (e.g., decreased heart rate variability 25 minutes systemic labor analgesia would be remifentanil, which is
after i.v. administration and 40 minutes after i.m. ad- metabolized by nonspecifi c plasma and tissue esterases.
ministration of pethidine) and in the neonate by central Th erefore, although remifentanil rapidly transfers across
nervous system depression (e.g., slowing of respiratory the placenta, fetal esterases will inactivate this new opi-
rate and changes in muscle tone). oid. Data regarding the use of remifentanil in parturi-
Th e adverse eff ects of pethidine and its active ents are limited, however, and so the drug cannot yet be
metabolite norpethidine on the fetus may—in rare in- recommended widely.
stances—need to be reversed by an opioid antagonist. It must be noted, though, that only a few drugs
Th e appropriate i.m. dose of naloxone would be 10 μg/ are considered “safe” regarding placental passage and
kg body weight. But ideally, naloxone—as most drugs in breastfeeding, but lack of data makes it advisable to
pain management, should be titrated intravenously to rely on individual judgment, if only a limited number of
its eff ect (the cumulative dose would be, as for i.m. ap- drugs are available.
plication, 10 μg/kg). Breast-feeding during maternal treatment with
If I have various opioids available, which one I paracetamol (acetaminophen) should be regarded as
would choose, and why? safe. Short-term use of nonsteroidal anti-infl ammatory
Onset time and context-sensitive half-life of all available drugs (NSAIDs) seems to be compatible with breast-
opioids are comparable, and so the potential to induce feeding. For long term-treatment, short-acting agents