OTHER OPIOID EFFECTS
Obstetrics
Morphine, but not fentanyl, can adversely affect in vitro fertilization
of sea urchin eggs. Thus, fentanyl has been recommended as clinically useful during
the harvesting of human ova for subsequent in vitro fertilization.[276]
Although alfentanil penetrates follicular fluid to a greater extent than fentanyl,
it has no effect on cleavage rate and has also been recommended as useful in providing
analgesia for oocyte retrieval. The teratogenic actions of opioids, including fentanyl,
sufentanil, and alfentanil, at least in animal models, appear to be minimal (also
see Chapter 58
).[277]
The parenteral administration of opioids prior to vaginal delivery
remains a commonly used method of analgesia. Nociception due to uterine cervical
distention could be suppressed by μ- and κ-agonists in rats,[278]
but the analgesic effect of μ-agonists but not κ-agonists was reduced by
estrogen.[279]
Aortocaval compression and associated
hypotension may be exacerbated by parenteral opioids, especially following morphine
or meperidine. Fetal manifestations of maternal opioid administration include decreases
in heart rate variability. Adverse neonatal effects can occur after either morphine
or meperidine administration to mothers. Fetal acidosis increases opioid transfer
from the mother. Attempts to minimize the neonatal effects of opioids include restricting
opioid administration to the first stage of labor. The short-acting opioid alfentanil
administered before cesarean delivery attenuated the maternal stress response, but
led to slightly reduced Apgar scores.[280]
Morphine has little effect on the pregnant rat uterus, whereas
meperidine can increase uterine contractions in a dose-dependent fashion that is
not reversible by naloxone.[281]
Fentanyl has no
effect on uterine blood flow and tone in sheep. Fentanyl (50–100 µg
IV every hour), compared with meperidine (25–50 mg IV every 2 to 3 hours),
results in less nausea, vomiting, and sedation in the mother and in lower naloxone
requirements in newborns.[282]
Morphine and meperidine have been found in the breast milk of
mothers receiving intravenous opioid analgesia.[283]
[284]
Although both fentanyl and morphine are concentrated
in breast milk in milk-to-plasma ratios of 2 to 3:1, newborn narcosis is reported
to be insignificant.
Newborns of addicted mothers can exhibit opioid withdrawal and
require observation and appropriate treatment.[285]
