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PubMed2005

Analysis of oxycodol and noroxycodol stereoisomers in biological samples by capillary electrophoresis.

A capillary electrophoresis (CE) method for the separation of the diastereoisomers of 6-oxycodol (6OCOL) and nor-6-oxycodol (N6OCOL), the 6-keto-reduced metabolites of oxycodone (OCOD) and noroxycodone (NOCOD), respectively, is reported and employed to assess the stereoselectivity of these metabolic steps in vivo, in vitro, and in chemical synthesis. CE in an untreated fused-silica capillary with acidic buffers containing 2-hydroxypropyl-beta-cyclodextrin, randomly sulfated beta-cyclodextrin, or single isomer heptakis(2,3-diacetyl-6-sulfato)-beta-cyclodextrin (HDAS-beta-CD) is shown to permit the simultaneous separation of the stereoisomers of 6OCOL and N6OCOL. A 100 mM phosphate buffer of pH 2.0 containing 2.05% w/v HDAS-beta-CD provides a medium for rapid analysis and unambiguous identification of these stereoisomers in solid-phase extracts of (i) urines stemming from patients under pharmacotherapy with OCOD, (ii) incubations of OCOD and NOCOD with human liver cytosol and the human liver S9 fraction, and (iii) after chemical synthesis from OCOD and NOCOD using NaBH(4). In all cases, alpha-N6OCOL is shown to be the predominant stereoisomer of N6OCOL. For 6OCOL, the same is true for in vitro formation and for chemical synthesis. In urine, however, beta-6OCOL is observed to be excreted in a higher amount than alpha-6OCOL. For the urinary alpha-/beta-isomer ratio of 6OCOL and N6OCOL, there are no differences between the data obtained for nonhydrolyzed and enzymatically hydrolyzed urines. The data document the stereoselectivity of the 6-keto-reduction of OCOD and NOCOD in man.

Electrophoresis, Capillary↗

PubMed1986

Extradural and parenteral pethidine as analgesia after total hip replacement: effects and kinetics. A controlled clinical study.

Twenty-one patients who had undergone total hip replacement were randomly assigned to one of three groups in order to compare a single dose of 1 mg/kg of pethidine im (I) and 20 mg (II) or 60 mg of extradural pethidine (III) in a double-blind design. The degree of analgesia, the adverse effects, and the kinetics were studied for 18 h. Pain was monitored using a visual analogue scale (VAS). Supplementary doses of oxycodone if required were given no earlier than 0.75 h after pethidine. Plasma concentrations of pethidine were measured with gas chromatography mass spectrometry (GCMS). Hypoalgesia to pin prick test was evaluated. Low pain scores were observed in the extradural groups between 0.25 and 1.5 h after the dose. A significant difference in pain score compared with the im group was found after the higher extradural dose only between 0.5 and 1 h (p less than 0.05). The area under the curve (AUC) of pain score versus time (0-18 h) was not significantly different between groups. The recorded adverse effects were minor in all three groups. The terminal half-lives and plasma clearances of pethidine, and the time to peak concentration were not different between the groups. Single patients in the extradural groups showed hypoalgesia to pin prick in parallel to the effect. The present study shows that extradural pethidine produces shortlived analgesia, in contrast to the long-lasting effect of morphine found in other studies.

Aged↗

PubMedDate not supplied

Preoperative diclofenac is a useful adjunct to spinal anesthesia for day-case varicose vein repair.

PURPOSE: To examine if preoperative diclofenac 50 mg or diazepam 10 mg po are useful adjuncts to spinal anesthesia for day-case varicose vein repair. METHODS: Two hundred ASA physical status I-II outpatients, age 18-60 yr, were randomized to receive either diclofenac 50 mg po or diazepam 10 mg po one hour before operation in a double-blind fashion (100 patients in both groups). If the patient was distressed or feared the spinal puncture and requested sedation, a bolus dose of alfentanil 0.5 mg was given i.v. as a rescue medication. On request, patients received diclofenac 50 mg po and, when needed, oxycodone 0.1 mg x kg(-1) im for postoperative pain relief. They were discharged with a supply of diclofenac 50 mg tablets and were asked to record postoperative pain using a visual analogue scale (VAS) and quantity of tablets taken. RESULTS: The VAS scores (+/- SD) eight hours after surgery, the next morning, and in the morning and at the end of the first and second postoperative days were 23 +/- 21, 12 +/- 17, 11 +/- 15, 8 +/- 15 and 8 +/- 15 in the diclofenac group, and 24 +/- 23, 12 +/- 20, 10 +/- 17, 8 +/- 16 and 7 +/- 14 in the diazepam group, respectively (NS). In the diclofenac and diazepam groups, 31% and 67% of the patients required postoperative diclofenac during the first eight postoperative hours (P <0.05). Diazepam premedication did not alter the number of patients who required alfentanil before spinal puncture. CONCLUSION: Diclofenac premedication reduced the analgesic requirements during the first eight hours after varicose vein repair.

Adolescent↗

PubMed2000

Diclofenac premedication but not intra-articular ropivacaine alleviates pain following day-case knee arthroscopy.

PURPOSE: To compare the postoperative analgesic effects of 50 mg diclofenac p.o. before surgery and intra-articular ropivacaine injected after diagnostic day-case knee arthroscopy performed under spinal anesthesia. METHODS: In a randomized, double-blind investigation, 200 ASA physical status 1-2 outpatients, age 18-60 yr, received either 50 mg diclofenac p.o. or placebo one hour before operation (100 patients per group), and intraarticular injections of either 20 ml of ropivacaine 0.5% or 20 ml of saline 0.9% (50 patients in each premedication groups). Patients received 50 mg diclofenac p.o. prn and, if needed, 0.1 mg x kg(-1) oxycodone im for postoperative pain relief. Patients were discharged home with a supply of 50 mg diclofenac tablets and were given a sheet of paper with knee pain VAS scales and a questionnaire of analgesics taken. Patients rated their VAS scores eight hours after surgery and in the moming and at the end of the first and the second postoperative days, respectively. RESULTS: The only statistically significant difference was found when the diclofenac groups were combined and compared with the combined placebo premedication groups. The VAS scores of knee pain at eight hours after the operation were 19+/-22 in the two diclofenac premedication groups and 32+/-28 in the two placebo groups (P = 0.001). CONCLUSIONS: Diclofenac premedication p.o. reduced the VAS scores at eight hours postoperatively while intra-articular ropivacaine did not.

Administration, Oral↗

PubMed2002

Determination of 6-oxo-morphinans, as the oximes, by difference circular dichroism spectroscopy.

A negative Cotton effect is observed in the circular dichroism (CD) spectra of 6-oxo-morphinans in the wavelength range of n-pi* electron transitions. 6-oxo-Morphinans can be transformed into oxime derivatives with hydroxylamine and after oxime formation the CD spectra are significantly different. Oxime formation was monitored by CD and by HPLC. It was established that under the experimental conditions used oxime formation was complete within 90 min. The method suggested for the determination of 6-oxo-morphinans is based on the considerable differences between the ellipticities before and after the oxime formation. The ellipticity difference varies linearly with concentration in the range 2 x 10(-5)-5 x 10(-4) mol L(-1) for the three 6-oxo-morphinans examined (oxycodone, hydrocodone, and 14-hydroxycodeinone). For hydrocodone the dependence is also linear in a lower concentration range (5 x 10(-6)-10(-4) mol L(-1)). The new difference CD spectroscopic method can be applied to the selective determination of 6-oxo-morphinans in bulk and dosage forms.

Circular Dichroism↗

PubMed1997

Ambulatory laparoscopic fundoplication.

BACKGROUND: Increasingly larger series of laparoscopic fundoplications (LF) are being reported. A well-documented advantage of the laparoscopic approach is shortened hospital stay. Most centers report typical lengths of stay (LOS) for LF of 2-3 days. Our success with LF with a LOS of 1 day led to an attempt at performing LF on an ambulatory basis. METHODS: Sixty-one consecutive patients with appropriate criteria for LF underwent surgery at our institution. Patients were counseled by the authors as to the usual postop course and progression of diet. All patients received preemptive analgesia (PEA) consisting of perioperative ketorolac and preincisional local infiltration with bupivicaine. Anesthetic management included induction with propofol, high-dose inhalational anesthetics, minimizing administration of parenteral narcotics, and avoidance of reversal of neuromuscular blockade. Immediate postop pain management included parenteral ketorolac and oral hydro- or oxycodone. All patients were given oral fluids and soft solids after transfer from the recovery room to the postoperative observation unit. Two patients were excluded from ambulatory consideration due to excessive driving distance from our hospital. Another two were hospitalized for observation after experiencing intraoperative technical problems. RESULTS: Of 57 patients in whom same-day discharge was attempted, there were three failures requiring overnight hospitalization: All were due to pain and nausea; one patient also suffered transient urinary retention. There were no adverse outcomes related to early discharge, and there were no readmissions. One patient returned to the emergency room after delayed development of urinary retention. Median time from conclusion of operation to discharge was less than 5 h. No patients expressed dissatisfaction with early discharge on follow-up interview. CONCLUSIONS: LF can be safely performed as an ambulatory procedure. Analgesic and anesthetic management should be tailored to minimize nausea and provide adequate pain control.

Adult↗

PubMed2006

Economic evaluation of Durogesic in moderate to severe, nonmalignant, chronic pain in Germany.

We carried out a cost-effectiveness evaluation of transdermal fentanyl compared to three other widely used opioids: transdermal buprenorphine, sustained-release morphine, and controlled-release oxycodone from a third-party-payers perspective. A decision analytic model with data from a structured database search and from panel data and assumptions was used to derive both cost and utility results. Probabilistic sensitivity analysis was performed to ensure the findings. Transdermal fentanyl patients gain more quality adjusted life-days or quality-adjusted life-years per euro. The incremental cost per quality-adjusted life-year is 1,625.65 euro for transdermal fentanyl compared to sustained-release morphine and 1,003.03 euro compared to CO, and it is cost-saving compared to transdermal buprenorphine (-203.38 euro per patient). Transdermal fentanyl is thus cost-effective compared to both sustained-release morphine and CO and dominant compared to transdermal buprenorphine in the treatment of adults with nonmalignant moderate to severe chronic pain.

Administration, Cutaneous↗

PubMed1986

Suppression of dental pain by the preoperative administration of flurbiprofen.

In a series of three studies involving dental outpatients undergoing removal of impacted third molars, preoperative and postoperative administration of flurbiprofen (Ansaid, Upjohn) led to superior pain relief when compared with acetaminophen alone or in combination with oxycodone. Patient preference and global evaluations clearly favored flurbiprofen. Side effects were mild and generally more common in patients receiving the opiate/mild analgesic combination. In two additional studies, flurbiprofen and etidocaine, a long-acting local anesthetic, also resulted in significantly less postoperative pain than a combination of acetaminophen/oxycodone and lidocaine; 67 percent of patients in the flurbiprofen plus etidocaine group reported no or only slight pain during the entire observation period. The greater analgesic efficacy of flurbiprofen appears to represent a genuine therapeutic advantage, since it is not achieved at the expense of greater side effects.

Acetaminophen↗

PubMed1986

Chronic use of opioid analgesics in non-malignant pain: report of 38 cases.

Thirty-eight patients maintained on opioid analgesics for non-malignant pain were retrospectively evaluated to determine the indications, course, safety and efficacy of this therapy. Oxycodone was used by 12 patients, methadone by 7, and levorphanol by 5; others were treated with propoxyphene, meperidine, codeine, pentazocine, or some combination of these drugs. Nineteen patients were treated for four or more years at the time of evaluation, while 6 were maintained for more than 7 years. Two-thirds required less than 20 morphine equivalent mg/day and only 4 took more than 40 mg/day. Patients occasionally required escalation of dose and/or hospitalization for exacerbation of pain; doses usually returned to a stable baseline afterward. Twenty-four patients described partial but acceptable or fully adequate relief of pain, while 14 reported inadequate relief. No patient underwent a surgical procedure for pain management while receiving therapy. Few substantial gains in employment or social function could be attributed to the institution of opioid therapy. No toxicity was reported and management became a problem in only 2 patients, both with a history of prior drug abuse. A critical review of patient characteristics, including data from the 16 Personality Factor Questionnaire in 24 patients, the Minnesota Multiphasic Personality Inventory in 23, and detailed psychiatric evaluation in 6, failed to disclose psychological or social variables capable of explaining the success of long-term management. We conclude that opioid maintenance therapy can be a safe, salutary and more humane alternative to the options of surgery or no treatment in those patients with intractable non-malignant pain and no history of drug abuse.

Adult↗

PubMedDate not supplied

Improved postoperative analgesia with morphine added to axillary block solution.

STUDY OBJECTIVE: To determine whether the addition of morphine to the axillary block local anesthetic solution provides improved or prolonged postoperative analgesia. DESIGN: Prospective, randomized, double-blind clinical trial with 24-hour follow-up. SETTING: Ambulatory unit of a large academic referral center. PATIENTS: Consecutive healthy volunteers scheduled for elective upper extremity surgery. INTERVENTIONS: Patients in the treatment group (AX) were given intravenous (IV) saline and had morphine 0.1 mg/kg added to their axillary block solution. Control subjects (CT) received morphine 0.1 mg/kg IV and had saline added to their axillary block solution. All axillary blocks were performed using 0.55 ml/kg of 1.5% lidocaine with epinephrine 1:200,000. MEASUREMENTS AND MAIN RESULTS: During the first 24 hours after surgery, visual analog scale (VAS) scores, supplementary analgesic (oxycodone 5 mg with acetaminophen 500 mg) use, and complications were recorded. Both groups had similar VAS scores throughout the study. In the 24-hour postoperative study period, AX patients required approximately half as many doses (median, 2 doses; range, 0 to 7 doses of supplemental analgesic as CT patients (median, 4 doses; range, 0 to 12 doses). There were no major complications in either group. CONCLUSIONS: The addition of morphine 0.1 mg/kg to the local anesthetic axillary block solution provided improved postoperative analgesia without an increased frequency of side effects or major complications.

Acetaminophen↗

PubMed2026

Opioid-sparing anesthesia based on opioid-free principles for early recovery after total knee arthroplasty: A randomized controlled trial.

OBJECTIVE: To evaluate whether an opioid-sparing anesthesia strategy (OSA), based on opioid-free anesthesia (OFA), improves early postoperative recovery quality and optimizes functional outcomes after total knee arthroplasty (TKA), compared with conventional opioid-based anesthesia (OBA). DESIGN: A randomized controlled trial with blinding of patients, surgeons, and outcome assessors. SETTING: Single center, July 2025 to February 2026. PATIENTS: 98 adult patients scheduled for elective unilateral TKA. INTERVENTION: Patients were randomized to the OSA or OBA group. The OSA regimen used esketamine and dexmedetomidine as the primary analgesic backbone, whereas the OBA regimen was opioid-based. Both groups received preoperative femoral nerve block and were administered oxycodone at skin incision and closure. Postoperatively, both groups received the same multimodal analgesia and patient-controlled analgesia. MEASUREMENTS: The primary outcome was the 24-h postoperative Quality of Recovery-15 (QoR-15) score. Secondary outcomes included 48-h QoR-15; Oxford Knee Score (OKS) and EQ-5D-3L at 1 and 3 months; high pain at 1 month and chronic postsurgical pain at 3 months. Exploratory outcomes included postoperative C-reactive protein (CRP), and postoperative nausea and vomiting (PONV), among others. RESULTS: At 24 h postoperatively, QoR-15 was higher in the OSA group than in the OBA group (118.4 ± 11.5 vs 113.3 ± 12.2; adjusted difference 5.12, 95% CI 0.51-9.74; P = 0.029), and this advantage persisted at 48 h (adjusted difference 5.54, 95% CI 1.57-9.52; P = 0.007). The OSA group had a lower incidence of PONV (P = 0.025) and lower postoperative CRP levels (P = 0.001). At 1 month, OKS was higher in the OSA group (adjusted difference 2.31, 95% CI 0.34-4.27; P = 0.022), with no significant differences in other secondary outcomes. CONCLUSION: In TKA, this OFA-based OSA strategy improved early postoperative QoR-15 scores. However, the QoR-15 difference did not reach the minimal clinically important difference, so its clinical relevance remains uncertain.

Humans↗

PubMedDate not supplied

Decreased postpartum use of oral pain medication after a single dose of epidural morphine.

BACKGROUND: Pain after vaginal delivery may result from episiotomy, perineal laceration, or uterine involution. Many women have indwelling epidural catheters in place at delivery. We hypothesized that a small dose of epidural morphine would be an effective strategy for postpartum analgesia. METHODS: Eighty-one healthy parturients receiving epidural analgesia for labor were enrolled. Patients were randomized in double-blind fashion to 1 of 3 groups: all groups received a 4-mL volume of epidural solution consisting of saline (group 1, control), 1 mg (group 2), or 2 mg morphine (group 3) after vaginal delivery. During the first 24 hours postpartum, patients were evaluated for the amount of oral pain medication requested; visual analog scale scores for pain at rest and with movement; satisfaction with postpartum pain treatment; and opioid side effects including nausea, pruritus, urinary retention, and respiratory depression. RESULTS: Patients who received 2 mg of epidural morphine used an average of 0.7 (0-1, interquartile range) opioid-containing pain pills (acetaminophen with codeine or oxycodone) compared with 1.2 (0-2) in the 1-mg group and 1.9 (0-3) in the control group ( P = .07). There was a statistically significant difference in oral drug usage between those who received epidural morphine and those who did not ( P < .03). There were no differences in side effects except that at 12 hours postpartum there was an increase in Foley catheterization in the 1-mg morphine group ( P = .007). CONCLUSIONS: These results suggest that epidural morphine decreases the need for oral pain medication in the first 24 hours postpartum. No significant dose-dependent side effects were found.

Adolescent↗

PubMedDate not supplied

The effect of cyclooxygenase-2 inhibition on acute and chronic donor-site pain after spinal-fusion surgery.

BACKGROUND AND OBJECTIVES: The development of chronic pain after spinal-fusion surgery represents a significant source of morbidity. One of the predictive factors for the development of chronic postsurgical pain is inadequate acute postoperative pain management. Further, the up-regulation of cyclooxygenase-2 (COX-2) after surgery may result in neuro-plastic changes that may contribute to a progression from acute to chronic pain. The goal of this prospective, randomized, double-blind study was to examine the effect of perioperative COX-2 inhibition on acute and chronic donor-site pain in patients undergoing spinal-fusion surgery. METHODS: Eighty patients scheduled to undergo instrumented posterior spinal fusion were randomized to either receive celecoxib 400 mg 1 hour before surgery, and then 200 mg every 12 hours after surgery for the first 5 days or receive matching placebo at similar time intervals. Patients were administered morphine via patient-controlled analgesia pump for the first 24 hours, and then acetaminophen and oxycodone tablets. Patients were asked to quantify their average pain on postoperative days 1 to 5. At 1 year after surgery, patients were questioned about the presence and subjective characteristics of any residual donor-site pain. RESULTS: Patients administered celecoxib reported lower pain scores and less opioid use during the first 5 postoperative days. Chronic donor-site pain was significantly higher (P<.01) in the placebo group (12 of 40, or 30%) compared with the celecoxib group (4 of 40, or 10%) at 1 year after surgery. CONCLUSIONS: The administration of celecoxib for the first 5 days after spinal-fusion surgery resulted in improved analgesia and a reduction in chronic donor-site pain at 1 year after surgery.

Acetaminophen↗

PubMed1984

Combination analgesics.

Six rationales for using combination analgesics are identified, but most combinations are formulated with two rationales in mind: enhancement of analgesia and reduction of adverse effects by combining two analgesics with different mechanisms of action. Acetaminophen and aspirin are the mainstays of oral analgesic combinations. There is substantial evidence that combining an optimal dose of acetaminophen or aspirin with an oral opioid such as codeine, hydrocodone, or oxycodone produces an additive analgesic effect greater than that obtained by doubling the dose of either constituent administered alone. There is also some evidence that the adverse effects produced by such combinations are less than would be produced by an equi-analgesic dose of a single constituent. The physician need not be confined to existing fixed-ratio combinations; he or she may extemporize to the patient's advantage by co-administering acetaminophen, aspirin, or other nonsteroidal anti-inflammatory drugs with available oral opioids and, in select situations, co-administering oral or injectable analgesics with psychoactive drugs.

Acetaminophen↗

PubMed2000

Intensive medical management of ureteral calculi.

OBJECTIVES: To compare two treatment regimens in patients with ureteral calculi. One regimen (control arm) used routine drugs, and the second regimen (treatment arm) used the same routine drugs plus uncommonly used drugs. METHODS: Between February and October 1998, 70 consecutive patients were evaluated for symptomatic ureteral calculi. Thirty-five patients were randomized to a control arm and received ketorolac, oxycodone, and acetaminophen combination tablets and prochlorperazine suppositories. Thirty-five patients were randomized to the treatment arm and received the same medications plus nifedipine XL, prednisone, and trimethoprim/sulfa combination tablets and plain acetaminophen. Stone passage rates, work days lost, emergency room visits, surgical interventions, and possible side effects of the drugs were recorded. RESULTS: The treatment arm (addition of nifedipine XL, prednisone, trimethoprim/sulfa, and plain acetaminophen) had higher (86% versus 56%) stone passage rates and fewer lost work days (mean 1.76 versus 4.9), emergency room visits (1 versus 4), and surgical interventions (2 versus 15). Both arms exhibited similar potential drug side effects. CONCLUSIONS: The addition of a calcium channel blocking agent, steroids, antibiotics, and more acetaminophen effected a higher stone passage rate and fewer lost work days, emergency room visits, and surgical interventions.

Absenteeism↗

PubMed1999

Distinction among eight opiate drugs in urine by gas chromatography-mass spectrometry.

Opiates are commonly abused substances, and forensic urine drug-testing for them requires gas chromatographic-mass spectrometric (GC-MS) confirmation. There are also medical reasons to test urine for opiates, and confirmation procedures other than GC-MS are often used for medical drug-testing. A thin-layer chromatographic (TLC) method distinguishes morphine, acetylmorphine, hydromorphone, oxymorphone, codeine, dihydrocodeine, hydrocodone, and oxycodone in clinical specimens. In certain clinical circumstances, GC-MS confirmation is requested for opiates identified by TLC, but, to our knowledge, no previous report examines all of the above opiates in a single GC-MS procedure. We find that they can be distinguished by GC-MS analyses of trimethylsilyl (TMS) ether derivatives, and identities of 6-keto opiates can be further confirmed by GC-MS analysis of methoxime (MO)-TMS derivatives. Inclusion of deuterium-labeled internal standards permits identification of the opiates in urine at concentrations below the TLC cutoff level of 600 ng/ml, and the GC-MS assay is linear over a concentration range that spans that level. This GC-MS procedure has proved useful as a third-stage identification step in a medical drug-testing sequence involving prior immunoassay and TLC.

Codeine↗

PubMedDate not supplied

A comparison of ketorolac tromethamine/oxycodone versus patient-controlled analgesia with morphine in anterior cruciate ligament reconstruction patients.

Effective postoperative analgesia with minimal side effects remains an important goal in enabling increasingly complex surgical procedures to be performed on an outpatient basis. In this study, we examined the efficacy of postoperative analgesia in 90 patients undergoing anterior cruciate ligament reconstruction using a patellar tendon autograft, with a 24-hour hospital stay. Patients were randomized to receive either intramuscular ketorolac supplemented by oral oxycodone, or intravenous morphine via patient-controlled analgesia (PCA) device, for postoperative analgesia. Patients were monitored for 2 hours in the recovery room, then every 4 hours until discharge, for the presence of complications of nausea, vomiting, urinary retention, pruritus, and dizziness. Pain was assessed using a visual analog scale (VAS) on the morning of postoperative day one. All patients were discharged by 24 hours after surgery. Ten (20%) of the patients receiving ketorolac/oxycodone versus 31 (79%) of those receiving PCA morphine experienced postoperative complications (P < .05). Postoperative nausea, vomiting, and urinary retention were each significantly more common in the PCA morphine group (P < .05). The incidence of pruritus and dizziness was low overall. There was no significant difference between groups in the severity of postoperative pain as assessed using a VAS. We conclude that ketorolac/oxycodone may provide comparable analgesia with fewer undesirable side effects than PCA morphine in patients undergoing anterior cruciate ligament reconstruction. Patients receiving ketorolac/oxymorphone may have a better quality recovery and more rapid discharge.

Analgesia, Patient-Controlled↗

PubMed1988

Sublingual absorption of selected opioid analgesics.

Ongoing interest in the improvement of pain management with opioid analgesics had led to the investigation of sublingual opioid absorption. The present report determined the percent absorption of selected opioid analgesics from the oral cavity of normal subjects under conditions of controlled pH and swallowing when a 1.0 ml aliquot of the test drug was placed under the tongue for a 10-minute period. Compared with morphine sulfate at pH 6.5 (18% absorption), buprenorphine (55%), fentanyl (51%), and methadone (34%) were absorbed to a significantly greater extent (p less than 0.05), whereas levorphanol, hydromorphone, oxycodone, heroin, and the opioid antagonist naloxone were not. Overall, lipophilic drugs were better absorbed than were hydrophilic drugs. Plasma morphine concentration-time profiles indicate that the apparent sublingual bioavailability of morphine is only 9.0% +/- 11.9% (SD) of that after intramuscular administration. In the same subjects the estimated sublingual absorption was 22.4% +/- 9.2% (SD), indicating that the sublingual absorption method may overestimate apparent bioavailability. When the oral cavity was buffered to pH 8.5, methadone absorption was increased to 75%. Thus, an alkaline pH microenvironment that favors the unionized fraction of opioids increased sublingual drug absorption. Although absorption was found to be independent of drug concentration, it was contact time dependent for methadone and fentanyl but not for buprenorphine. These results indicate that although the sublingual absorption and apparent sublingual bioavailability of morphine are poor, the sublingual absorption of methadone, fentanyl, and buprenorphine under controlled conditions is relatively high.

Administration, Sublingual↗