Transdermal fentanyl. A review of its pharmacological properties and therapeutic efficacy in pain control

Evaluation of transdermal fentanyl patches for analgesia in cats undergoing onychectomy

OBJECTIVE

To evaluate efficacy and safety of using transdermal fentanyl patches (TFP) for analgesia in cats undergoing onychectomy.

DESIGN

Randomized controlled clinical trial.

ANIMALS

45 client-owned cats weighing > or = 2.7 kg (5.9 lb) undergoing onychectomy, onychectomy and ovariohysterectomy, or onychectomy and castration.

PROCEDURE

Cats were randomly assigned to be treated with a TFP (25 micrograms/h) or butorphanol; TFP were applied a minimum of 4 hours before surgery (approx 8 hours prior to extubation). Rectal temperature, heart rate, respiratory rate, force applied by the forelimbs, and serum fentanyl concentration were measured, and temperament, recovery, degree of sedation, severity of pain, severity of lameness, and appetite were scored before and periodically for up to 40 hours after surgery.

RESULTS

Cats treated with a TFP had better recovery scores at 2 of 4 evaluation times, lower sedation scores at 2 of 8 evaluation times, and lower pain scores at 6 of 8 evaluation times, compared with cats treated with butorphanol. Use of a pressure-sensitive mat to evaluate force applied by the forelimbs did not reveal any differences between groups but did reveal a significant difference between preoperative and postoperative values. Mean +/- SD serum fentanyl concentrations were 1.56 +/- 1.08, 4.85 +/- 2.38, 4.87 +/- 1.56, and 4.35 +/- 2.97 ng/ml approximately 8, 24, 32, and 48 hours, respectively, after TFP placement.

CONCLUSIONS AND CLINICAL RELEVANCE

Results suggest that use of a TFP (25 micrograms/h) for postoperative analgesia in cats undergoing onychectomy with or without surgical sterilization is safe and effective.

Respiratory failure due to the combined effects of transdermal fentanyl and epidural bupivacaine/diamorphine following radical nephrectomy

The transdermal therapeutic system (TTS) fentanyl has been designed for rate-controlled drug delivery. When the system is applied, a fentanyl depot concentrates in the upper skin layers. Plasma concentrations are not measurable until 2 hours after application, and it takes an 8-16 hr latency period until full clinical fentany effects are observed. Following removal, serum fentanyl concentrations decline gradually and fall to about 50% in approximately 16 hours. We report the case of a 77-year-old man with a history of severe arthritis, who was receiving transdermal fentanyl and developed respiratory failure after starting epidural diamorphine/bupivacaine for postoperative pain relief following radical nephrectomy.

Pediatric acute pain management

The past decade has brought about an explosion of knowledge about the physiology of nociception and many new techniques for pain relief, new analgesic drugs, and new applications of old analgesic drugs. These techniques include methods of opioid administration by transdermal and transmucosal absorption and the use of neuraxial analgesia for the management of pain in children. Interest in the use of regional anesthesia in children has been rekindled, and analgesic properties and pre-emptive analgesic properties of many agents not typically considered analgesics, such as clonidine and ketamine, have been recognized. Perhaps the greatest advance has been the paradigm shift in the recognition that pain not only exists in infants and children but also is a significant cause of morbidity and even mortality. Given the unprecedented interest in pain management in adults and children, physicians can now look forward to the development of new methods of drug delivery and of receptor-specific drugs that divorce analgesia from the untoward side effects of existing analgesics. Improvement in the quality of life of hospitalized children also will occur.

Patient-controlled intranasal analgesia: effective alternative to intravenous PCA for postoperative pain relief

PURPOSE

To investigate whether the nasal route for fentanyl administration in patient-controlled analgesia (PCA) provides as effective postoperative analgesia as intravenous PCA.

METHODS

Patient-controlled intranasal or intravenous analgesia with fentanyl was investigated in 48 patients (ASA I-III) on the day of surgery (orthopedic, abdominal or thyroid) in a prospective, randomized, double-blind, double-dummy study. Fentanyl was given in a bolus of 25 microg for intranasal and 17.5 microg for i.v. PCA, lockout interval six minutes. The first requested dose was doubled in both groups. Pain intensity (101-point numerical rating scale) and vital parameters were observed at 11 measurement points during the 240 min study. Patients were asked for side effects at every measurement point and for their satisfaction at the end of the study by the same investigator (J.M.).

RESULTS

Onset of analgesia, the first reduction in pain intensity on the numerical rating scale, was 21 +/- 11 min (range 15-45 min) in intranasal and 22 +/- 16 min (range 15-90 min) in i.v. PCA. Pain intensity was reduced from 55 +/- 11 to 11 +/- 10 in the intranasal group and from 53 +/- 8 to 11 +/- 6 in the i.v. PCA group. Vital parameters remained stable and side effects were comparable in both groups. The judgement "excellent" or "good" was given by 21 of 23 patients treated intranasally and 24 of 25 patients treated intravenously.

CONCLUSION

Intranasal PCA with fentanyl was an effective alternative to i.v. PCA in postoperative patients.

Constipation and the use of laxatives: a comparison between transdermal fentanyl and oral morphine

Constipation and the use of laxatives were investigated in patients with chronic cancer pain treated with oral morphine and transdermal fentanyl in an open sequential trial. Forty-six patients were treated with slow-release morphine 30-1000 mg/day for 6 days and 39 of these patients were switched to transdermal fentanyl 0.6-9.6 mg/day with a conversion ratio of 100:1. Median fentanyl doses increased from 1.2 to 3.0 mg/day throughout the 30-day transdermal treatment period. Twenty-three patients completed the study. Two patients died from the basic disease while treated with transdermal fentanyl, 12 patients were excluded for various reasons, and not enough data for evaluation were available for two patients. Mean pain intensity decreased slightly after conversion although the number of patients with breakthrough pain or requiring immediate-release morphine as a rescue medication was higher with transdermal fentanyl. The number of patients with bowel movements did not change after the opioid switch but the number of patients taking laxatives was reduced significantly from 78-87% of the patients per treatment day (morphine) to 22-48% (fentanyl). Lactulose was used mainly and was reduced most drastically, but other laxatives were also used less frequently. In this study transdermal fentanyl was associated with a significantly lower use of laxatives compared to oral morphine. The difference in the degree of constipation between the two analgesic regimens should be confirmed in a randomized double-blind study that takes into account both constipation and use of laxatives.

Clinical pharmacokinetics of transdermal opioids: focus on transdermal fentanyl

Transdermal delivery allows continuous systemic application of opioids through the intact skin. This review analyses the pharmacokinetic properties of transdermal opioid administration in the context of clinical experience, with a focus on fentanyl. A transdermal therapeutic system (TTS) for fentanyl has been developed. The amount of fentanyl released is proportional to the surface area of the TTS, which is available in different sizes. After the first application of a TTS, a fentanyl depot concentrates in the upper skin layers and it takes several hours until clinical effects are observed. The time from application to minimal effective and maximum serum concentrations is 1.2 to 40 hours and 12 to 48 hours, respectively. Steady state is reached on the third day, and can be maintained as long as patches are renewed. Within each 72-hour period, serum concentrations decrease gradually over the second and third days. When a TTS is removed, fentanyl continues to be absorbed into the systemic circulation from the cutaneous depot. The terminal half-life for TTS fentanyl is approximately 13 to 25 hours. The interindividual variability of serum concentrations, partly caused by different clearance rates, is markedly larger than the intraindividual variability. The effectiveness of TTS fentanyl was first demonstrated in acute postoperative pain. However, the slow pharmacokinetics and large variability of TTS fentanyl, together with the relatively short duration of postoperative pain, precluded adequate dose finding and led to inadequate pain relief or, especially, a high incidence of respiratory depression; such use is now contraindicated. Conversely, in cancer pain, TTS fentanyl offers an interesting alternative to oral morphine, and its effectiveness and tolerability in this indication has been demonstrated by a number of trials. Its usefulness in chronic pain of nonmalignant origin remains to be confirmed in controlled trials. In general, TTS fentanyl produces the same adverse effects as other opioids, mainly sedation, nausea, vomiting and constipation. In comparison with oral morphine, TTS fentanyl causes fewer gastrointestinal adverse events. The risk of hypoventilation is comparatively low in cancer patients. Sufentanil and buprenorphine may also be suitable for transdermal delivery, but clinical results are not yet available. Transdermal morphine is only useful if applied to de-epithelialised skin. However, iontophoresis may allow transdermal administration of opioids, including morphine, with a rapid achievement of steady state concentrations and the ability to adjust delivery rates. This would be beneficial for acute and/or breakthrough pain, and initial clinical trials are in progress.

Novel Drug Delivery Systems

Interest in pain management is growing, with the emerging demand by our patients and colleagues, for pain relief. To meet that need, pharmaceutical and medical technology companies have provided the medical field with a variety of choices and options to deliver medication for pain control. Examination and review of the present systemic options are introduced. A more detailed look at the intrathecal route is necessary because of the tremendous potential for receptor-targeted drug delivery. The ability to treat nociceptive and neuropathic pain with drug-specific therapy makes this system all the more exciting. Because of this future, a wealth of new and old drugs are being found or reexamined for their use.

Comparison of transdermal fentanyl and intramuscular oxymorphone on post-operative behaviour after ovariohysterectomy in dogs

The effects of transdermal fentanyl and i.m. oxymorphone on behavioural and physiological responses, after ovariohysterectomy in dogs, were investigated. The study involved three groups of 10 dogs: fentanyl/surgery (FS), oxymorphone/surgery (OS), fentanyl/control (FC). A transdermal fentanyl delivery system (50 microg hour(-1)) (FS and FC) was applied 20 hours before surgery, or i.m. oxymorphone (OS) was administered. After ovariohysterectomy (FS and OS) or anaesthesia alone (FC), dogs were continuously videotaped for 24 hours and a standardised hourly interaction with a handler performed. The videotapes were analysed, and interactive and non-interactive behaviours evaluated. In addition, pain and sedation scores, pulse and respiratory rates, rectal temperature, arterial blood pressure, plasma cortisol and plasma fentanyl concentrations were measured. This study showed that transdermal fentanyl and i.m. oxymorphone (0.05 mg kg(-1)) produced comparable analgesic effects over a 24 hour recording period. I.m. oxymorphone produced significantly more sedation and lower rectal temperatures than transdermal fentanyl. There were no significant differences between groups in respiratory and heart rates, and arterial blood pressures.