CLINICAL PHARMACOLOGY
Pharmacology
SUFENTA (sufentanil citrate injection) is an opioid analgesic. When used in balanced general anesthesia, SUFENTA (sufentanil citrate injection)
has been reported to be as much as 10 times as potent as fentanyl. When administered
intravenously as a primary anesthetic agent with 100% oxygen, SUFENTA (sufentanil citrate injection) is approximately
5 to 7 times as potent as fentanyl. Assays of histamine in patients administered
SUFENTA (sufentanil citrate injection) have shown no elevation in plasma histamine levels and no indication
of histamine release. (See dosage chart for
more complete information on the intravenous use of SUFENTA.)
Pharmacodynamics
Intravenous use
At intravenous doses of up to 8 µg/kg, SUFENTA (sufentanil citrate injection) is an analgesic component of general anesthesia; at intravenous doses ≥ 8 µg/kg, SUFENTA (sufentanil citrate injection) produces a deep level of anesthesia. SUFENTA (sufentanil citrate injection) produces a dose related attenuation of catecholamine release, particularly norepinephrine. At intravenous dosages of ≥ 8 µg/kg, SUFENTA (sufentanil citrate injection) produces hypnosis and anesthesia without the use of additional anesthetic agents. A deep level of anesthe-sia is maintained at these dosages, as demonstrated by EEG patterns. Dosages of up to 25 µg/kg attenuate the sympathetic response to surgical stress. The catecholamine response, particularly norepinephrine, is further attenuated at doses of SUFENTA (sufentanil citrate injection) of 25-30 µg/kg, with hemodynamic stability and preserva-tion of favorable myocardial oxygen balance.
SUFENTA (sufentanil citrate injection) has an immediate onset of action, with relatively limited accumulation. Rapid elimination from tissue storage sites allows for relatively more rapid recovery as compared with equipotent dosages of fentanyl. At dosages of 1-2 µg/kg, recovery times are comparable to those observed with fentanyl; at dosages of > 2-6 µg/kg, recovery times are comparable to enflurane, isoflurane and fentanyl. Within the anesthetic dosage range of 8-30 µg/kg of SUFENTA, recovery times are more rapid compared to equipotent fentanyl dosages.
The vagolytic effects of pancuronium may produce a dose dependent elevation in heart rate during SUFENTA-oxygen anesthesia. The use of moderate doses of pancuronium or of a less vagolytic neuromuscular blocking agent may be used to maintain a stable lower heart rate and blood pressure during SUFENTA-oxygen anesthesia. The vagolytic effects of pancuronium may be reduced in patients administered nitrous oxide with SUFENTA. Preliminary data suggest that in patients administered high doses of SUFENTA, initial dosage requirements for neuromuscular blocking agents are generally lower as compared to patients given fentanyl or halothane, and comparable to patients given enflurane.
Bradycardia is infrequently seen in patients administered SUFENTA-oxygen anesthesia. The use of nitrous oxide with high doses of SUFENTA (sufentanil citrate injection) may decrease mean arterial pressure, heart rate and cardiac output.
SUFENTA (sufentanil citrate injection) at 20 µg/kg has been shown to provide more adequate reduction in intracranial
volume than equivalent doses of fentanyl, based upon require-ments for furosemide
and anesthesia supplementation in one study of patients undergoing craniotomy.
During carotid endarterectomy, SUFENTA-nitrous oxide/oxygen produced reductions
in cerebral blood flow comparable to those of enflurane-nitrous oxide/oxygen.
During cardiovascular surgery, SUFENTA-oxygen produced EEG patterns similar
to fentanyl-oxygen; these EEG changes were judged to be compatible with adequate
general anesthesia. The intraoperative use of SUFENTA (sufentanil citrate injection) at anesthetic dosages
maintains cardiac output, with a slight reduction in systemic vascular resistance
during the initial postoperative period. The incidence of postoperative hypertension,
need for vasoactive agents and requirements for postoperative analgesics are
generally reduced in patients administered moderate or high doses of SUFENTA (sufentanil citrate injection)
as compared to patients given inhalation agents. Skeletal muscle rigidity is
related to the dose and speed of administration of SUFENTA. This muscular rigidity
may occur unless preventative measures are taken (see WARNINGS).
Decreased respiratory drive and increased airway resistance occur with SUFENTA. The duration and degree of respiratory depression are dose related when SUFENTA (sufentanil citrate injection) is used at sub-anesthetic dosages. At high doses, a pronounced decrease in pulmonary exchange and apnea may be produced.
Epidural use in Labor and Delivery
Onset of analgesic effect occurs within approximately 10 minutes of administration of epidural doses of SUFENTA (sufentanil citrate injection) and bupivacaine. Duration of analgesia following a single epidural injection of 10-15 µg SUFENTA (sufentanil citrate injection) and bupivacaine 0.125% averaged 1.7 hours.
During labor and vaginal delivery, the addition of 10-15 µg SUFENTA (sufentanil citrate injection) to 10 mL 0.125% bupivacaine provides an increase in the duration of analgesia com-pared to bupivacaine without an opioid. Analgesia from 15 µg SUFENTA (sufentanil citrate injection) plus 10 mL 0.125% bupivacaine is comparable to analgesia from 10 mL of 0.25% bupivacaine alone. Apgar scores of neonates following epidural administration of both drugs to women in labor were comparable to neonates whose mothers received bupivacaine without an opioid epidurally.
Pharmacokinetics
Intravenous use
The pharmacokinetics of intravenous SUFENTA (sufentanil citrate injection) can be described as a three-compartment model, with a distribution time of 1.4 minutes, redistribution of 17.1 minutes and elimination half-life of 164 minutes in adults. The elimination half-life of SUFENTA (sufentanil citrate injection) is shorter (e.g. 97 ± 42 minutes) in infants and children, and longer in neonates (e.g. 434 ± 160 minutes) compared to that of adolescents and adults. The liver and small intestine are the major sites of biotransformation. Approximately 80% of the administered dose is excreted within 24 hours and only 2% of the dose is eliminated as unchanged drug. Plasma protein binding of sufentanil, related to the alpha acid glycoprotein concentration, was approximately 93% in healthy males, 91% in mothers and 79% in neonates.
Epidural use in Labor and Delivery
After epidural administration of incremental doses totaling 5-40 µg SUFENTA (sufentanil citrate injection) during labor and delivery, maternal and neonatal sufentanil plasma concen-trations were at or near the 0.05-0.1 ng/mL limit of detection, and were slightly higher in mothers than in their infants.
CLINICAL STUDIES
Epidural use in Labor and Delivery
Epidural sufentanil was tested in 340 patients in two (one single-center and one multicenter) double-blind, parallel studies. Doses ranged from 10 to 15 µg sufentanil and were delivered in a 10 mL volume of 0.125% bupivacaine with and without epinephrine 1:200,000. In all cases sufentanil was administered following a dose of local anesthetic to test proper catheter placement. Since epidural opioids and local anesthetics potentiate each other, these results may not reflect the dose or efficacy of epidural sufentanil by itself.
Individual doses of 10-15 µg SUFENTA (sufentanil citrate injection) plus bupivacaine 0.125% with epinephrine provided analgesia during the first stage of labor with a duration of 1-2 hours. Onset was rapid (within 10 minutes). Subsequent doses (equal dose) tended to have shorter duration. Analgesia was profound (complete pain relief) in 80% to 100% of patients and a 25% incidence of pruritus was observed. The duration of initial doses of SUFENTA (sufentanil citrate injection) plus bupivacaine with epinephrine is approximately 95 minutes, and of subsequent doses, 70 minutes.
There are insufficient data to critically evaluate neonatal neuromuscular and adaptive capacity following recommended doses of maternally administered epidural sufentanil with bupivacaine. However, if larger than recommended doses are used for combined local and systemic analgesia, e.g. after adminis-tration of a single dose of 50 µg epidural sufentanil during delivery, then impaired neonatal adaption to sound and light can be detected for 1 to 4 hours and if a dose of 80 µg is used impaired neuromuscular coordination can be detected for more than 4 hours.
Animal Toxicology
The intravenous LD50 of SUFENTA (sufentanil citrate injection) is 16.8 to 18.0 mg/kg in mice, 11.8 to 13.0 mg/kg in guinea pigs and 10.1 to 19.5 mg/kg in dogs. Reproduction studies performed in rats and rabbits given doses of up to 2.5 times the upper human intravenous dose for a period of 10 to over 30 days revealed high maternal mortality rates due to decreased food consumption and anoxia, which preclude any meaningful interpretation of the results. Epidural and intrathecal injections of sufentanil in dogs and epidural injections in rats were not associated with neurotoxicity.