Clinical pharmacokinetics of transdermal opioids: focus on transdermal fentanyl

Long-term management of noncancer pain with transdermal therapeutic system-fentanyl

Transdermal therapeutic system-fentanyl (TTS-F) has been extensively studied in cancer pain management. However, few studies have addressed the long-term management of noncancer pain, especially when it relates to neuropathic pain. A total of 529 patients were recruited into this prospective open-label study to determine the safety and effectiveness of TTS-F in relation to quality-of-life (QOL) stratified according to pain type and etiology. TTS-F significantly improves QOL within 28 days, and pain management within 48 hours. The frequency of side effects rapidly decreases over time, and patients not experiencing adequate pain management are identified within 28 days. The median duration of therapy for effective pain management was 10 months, and 90% of patients sustained such efficacy. TTS-F offers statistically significant increases in QOL-Short Form 12 (including the Physical Component Scale and Mental Component Scale measures) and pain control (Greek Brief Pain Inventory) from one time point to the next (P <.0001). These improvements are not influenced by pain type or etiology. TTS-F is a safe and effective pain management system independent of patient characteristics and demographic factors. What is of most importance is that in those patients with neuropathic pain, for whom opioids have long been thought to be ineffective, similar effectiveness is demonstrated when compared to patients with nociceptive pain.

The assessment and management of chronic pain in children

Chronic pain in children and adolescents is frequently misdiagnosed by caregivers. It is not treated until it results in the loss of routine ability and function. Chronic pain is often associated with underlying diseases commonly seen in childhood, including sickle cell disease, malignancy, rheumatologic disorders, inflammatory bowel disease, trauma, and states where there is no identifiable etiology. Chronic pain differs from acute pain in that it serves no useful function. Untreated or under-treated chronic pain will result in the unnecessary suffering of the patient, disruption of family routine, and cohesiveness and restriction of the child's daily activities, thereby increasing long-term disability. Accurate and repeated assessment of chronic pain is required for therapy to be effective. Assessment of chronic pain in children is difficult due to their developing cognitive abilities. The assessment of childhood pain varies with the child's age, type of pain, situation, and prior painful experiences. Assessment tools such as the Varni-Thompson Pediatric Pain Questionnaire and the Visual Analog Scale are helpful for both the patient and physician in helping to identify situations that precipitate pain, to rate the level of pain and determine if therapy has been effective. Documentation of pain assessments and the effectiveness of interventions in the medical record should be included as a routine part of all patient records. Most caregivers have extensive experience in the treatment of acute pain in children but are often not comfortable with the management of complicated and chronic pain states. The therapy for chronic pain in children is multifactorial. It can include agents from multiple classes of pharmacologic agents (nonsteroidal anti-inflammatory drugs, opioids, tricyclic antidepressants, and antineuroleptics) nonconventional therapies (acupuncture and pressure and aromatherapy), as well as herbal and homeopathic remedies.

Benefit-Risk Assessment of Transdermal Fentanyl for the Treatment of Chronic Pain

Transdermal fentanyl is effective and well tolerated for the treatment of chronic pain caused by malignancy and non-malignant conditions when administered according to the manufacturer's recommendations. Compared with oral opioids, the advantages of transdermal fentanyl include a lower incidence and impact of adverse effects (constipation, nausea and vomiting, and daytime drowsiness), a higher degree of patient satisfaction, improved quality of life, improved convenience and compliance resulting from administration every 72 hours, and decreased use of rescue medication. Transdermal fentanyl is a useful analgesic for cancer patients who are unable to swallow or have gastrointestinal problems. Transdermal fentanyl forms a depot within the upper skin layers before entering the microcirculation. Therapeutic blood levels are attained 12-16 hours after patch application and decrease slowly with a half-life of 16-22 hours following removal. Patients with chronic pain should be titrated to adequate relief with short-acting oral or parenteral opioids prior to the initiation of transdermal fentanyl in order to prevent exacerbations of pain or opioid-related adverse effects. Transdermal fentanyl can then be initiated based on the 24-hour opioid requirement once adequate analgesia has been achieved. The prolonged elimination of transdermal fentanyl can become problematic if patients develop opioid-related adverse effects, especially hypoventilation. Adverse effects do not improve immediately after patch removal and may take many hours to resolve. Patients who experience opioid-related toxicity associated with respiratory depression should be treated immediately with an opioid antagonist such as naloxone and closely monitored for at least 24 hours. Because of the short half-life of naloxone, sequential doses or a continuous infusion of the opioid antagonist may be necessary. Transdermal fentanyl should be administered cautiously to patients with pre-existing conditions such as emphysema that may predispose them to the development of hypoventilation. Transdermal fentanyl is indicated only for patients who require continuous opioid administration for the treatment of chronic pain that cannot be managed with other medications. It is contraindicated in the management of acute and postoperative pain, as pain may decrease more rapidly in these circumstances than fentanyl blood levels can be adjusted, leading to the development of life-threatening hypoventilation. Cognitive and physical impairments such as confusion and abnormal co-ordination can occur with transdermal fentanyl. Therefore, patients should be instructed to refrain from driving or operating machinery immediately following the initiation of transdermal fentanyl, or after any dosage increase. Patients may resume such activities once the absence of these potential adverse effects is documented.

Comparison of TTS-fentanyl with sustained-release oral morphine in the treatment of patients not using opioids for mild-to-moderate pain

OBJECTIVE

This randomised, multicentre, direct open comparative trial evaluated the efficacy, treatment convenience, tolerability and safety aspects of transdermal therapeutic system (TTS)-fentanyl and sustained-release oral morphine (SRM) in both opioid-naïve patients with moderate-to-severe cancer-related pain and in patients who had already been using opioids for mild-to-moderate pain. The two treatment groups were run in parallel. Special attention was paid to constipation, nausea/vomiting, drowsiness and respiratory depression.

PATIENTS AND METHODS

The 131 enrolled patients started the 4-week treatment at low doses of opioid (25 microg/h TTS-fentanyl for 3 days or 30 mg SRM every 12 h) and were individually titrated. Tolerability, efficacy and safety were assessed throughout the study period. Frequency of constipation was the primary study variable and accordingly the study was powered for this. Both patients and investigators made a global treatment evaluation.

RESULTS

TTS-fentanyl and SRM were shown to be equally effective. Pain control and sleep quality improved with both treatments. None of the patients developed respiratory depression. Statistically significantly more patients in the SRM treatment group discontinued the trial prematurely (59% vs 27%; p < 0.001), particularly due to adverse events (36% vs 4%; p < 0.001). Fewer patients in the TTS-fentanyl than in the SRM treatment group reported constipation during the trial. This finding was statistically significant after 1 week of treatment (27% vs 57%; p = 0.003). The favourable tolerability profile of TTS-fentanyl was also reflected in both the patient and the investigator global evaluation of the treatment. Patient assessment favoured TTS-fentanyl treatment in terms of a significantly lower rate of troublesome side-effects ('quite a bit' to 'very much' troublesome side-effects in 14% vs 36% of patients; p = 0.003) and less interruption of daily activities (absence of any interruption of daily activities in 88% vs 63% of patients; p = 0.012). Investigators scored TTS-fentanyl as significantly better with respect to 'side-effects' (p = 0.039) and 'overall impression' (p = 0.013). Sub-analyses of opioid-naïve users gave similar results.

CONCLUSION

These data indicate that TTS-fentanyl, when used as an opioid of first choice in the treatment of cancer-related pain, is as effective as, but better tolerated than, SRM, including in opioid-naïve patients.

The effects of iontophoresis and electroporation on transdermal delivery of buprenorphine from solutions and hydrogels

The in-vitro permeation of buprenorphine across skin was investigated to assess the effects of iontophoresis and electroporation on drug permeation from solutions as well as from hydrogels. Iontophoresis (0.3 mA cm(-2)) increased the buprenorphine permeation from solution by a factor of 14.27 as compared with passive diffusion; the application of electroporation increased the buprenorphine permeation from solutions by a factor of 8.45. The permeation experiments using cellulose membrane and stratum corneum (SC)-stripped skin as permeation barriers suggested that the enhancement with iontophoresis was primarily due to strong electrophoretic drift of buprenorphine molecules, whereas the enhancement seen with electroporation was mainly attributed to the creation of transient aqueous pores in the SC layer. Application of high-voltage pulses followed by iontophoresis resulted in a shorter permeation onset time from both solutions and hydrogels as compared with iontophoresis or electroporation alone. The charge repulsion between buprenorphine and chitosan vehicles as well as the competition effects of counter-ions for carboxymethylcellulose (CMC)-based polymers may account for the different permeation rates under electrical field. This study demonstrates the feasibility of using hydrogels for delivery of buprenorphine under the application of iontophoresis or electroporation, separately or together.

Fentanyl-associated syndrome of inappropriate antidiuretic hormone secretion

A 43-year-old woman with advanced pulmonary blastoma was admitted for worsening back pain. Her drug regimen included hydromorphone and benazepril. On admission, hydromorphone patient-controlled analgesia (PCA) was started for acute pain control and dexamethasone for possible cord compression. Baseline laboratory tests were unremarkable, but magnetic resonance imaging revealed T3 and L3 lesions. Irradiation was started with improvement in her pain. In anticipation of discharge, a fentanyl transdermal patch was given, and PCA was tapered. Two days later, the patient became progressively confused and fell. Neurologic examination and computed brain tomography were normal. Her serum sodium was 119 mEq/L (normal 136-144 mEq/L) and was confirmed on repeat testing, urine sodium was 194 mEq/L, and urine and serum osmolalities were 554 mOsm/kg (normal 300-900 mOsm/kg) and 245 mOsm/kg (normal 280-300 mOsm/kg), respectively, consistent with the syndrome of inappropriate antidiuretic hormone secretion (SIADH). Fluids were restricted, hydromorphone PCA was started again, and fentanyl was discontinued. After 36 hours, her serum sodium increased to 136 mEq/L. Because we were unsure whether the fentanyl or her cancer was causative and were unable to find any published reports of fentanyl-associated SIADH, we readministered the fentanyl patch 2 days later. Within 48 hours, serum sodium dropped to 123 mEq/L. Fentanyl was discontinued, fluids were restricted, and 3% saline was started. Her serum sodium increased to 132 mEq/L in 48 hours. The patient was prescribed oral hydromorphone and benazepril and was discharged. The repeated temporal relationship between the administration of fentanyl and the onset of SIADH strongly implicates fentanyl as the causative agent in this case. To our knowledge, this is the first report of fentanyl-associated SIADH.

Costs of opioid therapy for chronic nonmalignant pain in Germany: an economic model comparing transdermal fentanyl (Durogesic) with controlled-release morphine

The fentanyl transdermal therapeutic system (fentanyl-TTS;Durogesic) has a distinct route of administration and safety profile compared with other opioids used in the treatment of moderate to severe pain.These aspects are likely to have an impact on patient acceptance and functioning as well as efficacy. We compared the cost-utility of fentanyl-TTS and controlled-release morphine (cr-morphine) in the treatment of moderate to severe nonmalignant pain in outpatients in Germany. A 1-year, three-phased decisionanalytic model was constructed, incorporating estimates of a variety of aspects of pain control.Use of fentanyl-TTS was predicted to incur higher costs than cr-morphine over 1 year of treatment (DM 6950 vs.DM 6186, respectively) but was associated with a higher number of quality-adjusted life days (234 vs. 216, respectively), thus achieving an incremental cost-utility ratio of DM 15,960 per quality-adjusted life-year gained.The results of the decision-analytic model support the use of fentanyl-TTS as a favorable cost-effective option for the treatment of moderate to severe nonmalignant pain.

Electrically modulated transdermal delivery of fentanyl

PURPOSE

Test to determine if iontophoresis and electroporation, alone or in combination, can be used for rapid and modulated delivery of fentanyl.

METHODS

Fentanyl citrate (5 mg/ml) dissolved in pH 4.0 citrate buffer was delivered in vitro across human epidermis. For iontophoresis. a current of 0.5 mA/cm2 was applied for 5 h, using silver/silver chloride electrodes. Electroporation protocol consisted of applying 15 exponential pulses of 500V (applied voltage) and 200 msec duration at the rate of 1 pulse per minute at time zero and, in some cases, repeating at 1.5 and 2.5 h.

RESULTS

There was no measurable permeation of fentanyl through human epidermis under passive conditions. A significant flux (about 80 microg/cm2-hr) was achieved using iontophoresis and decreased once the current was turned off. A 4-fold higher flux and shorter lag time was observed with electroporation as compared to iontophoresis. The flux was found to recover quickly (within 1 h) following pulsing. Modulation of transdermal delivery of fentanyl was demonstrated by both iontophoresis and electroporation.

CONCLUSIONS

Electrically assisted transdermal delivery of fentanyl significantly increased transport compared to passive delivery. Also, rapid and modulated delivery was shown to be feasible by programming the electrical parameters.

Transdermal fentanyl: an updated review of its pharmacological properties and therapeutic efficacy in chronic cancer pain control

Fentanyl is a synthetic opioid agonist which interacts primarily with the mu-opioid receptor. The low molecular weight, high potency and lipid solubility of fentanyl make it suitable for delivery by the transdermal therapeutic system. These patches are designed to deliver fentanyl at a constant rate (25, 50, 75 and 100 microg/h), and require replacement every 3 days. Data from randomised, nonblind trials suggest that transdermal fentanyl is as effective as sustained-release oral morphine in the treatment of chronic cancer pain, as reported by patients using visual and numerical analogue scales as well as verbal description scales. No obvious differences in health-related quality of life were found in patients with chronic cancer pain when comparing transdermal fentanyl with sustained-release oral morphine. Nevertheless, significantly more patients expressed a preference for transdermal fentanyl than for sustained-release oral morphine after a randomised, nonblind, crossover trial. Because of the formation of a fentanyl depot in the skin tissue, serum fentanyl concentrations increase gradually following initial application, generally levelling off between 12 and 24 hours. Thereafter, they remain relatively constant, with some fluctuation, for the remainder of the 72-hour application period. Once achieved, steady-state plasma fentanyl concentrations can be maintained for as long as the patches are renewed. The most frequently observed adverse events during transdermal fentanyl administration (as with other opioid agonists) included vomiting, nausea and constipation. Data from a nonblind, randomised trials suggest that constipation occurs less frequently in patients receiving transdermal fentanyl than in those given sustained-release oral morphine. The most serious adverse event reported in US premarketing trials was hypoventilation, which occurred with an incidence of approximately 2%. Adverse reactions related to skin and appendages (i.e. rash and application site reactions - erythema, papules, itching and oedema) were reported in 153 patients with cancer at a frequency between 1 and 3%.

CONCLUSION

Transdermal fentanyl is a useful opioid-agonist for the treatment of moderate to severe chronic cancer pain. The advantages of transdermal fentanyl include ease of administration and the 3-day application interval. These factors coupled with a lower incidence of constipation are likely to contribute to the reported patient preference of transdermal fentanyl over sustained-release oral morphine.

Treatment of cancer pain with transdermal fentanyl

Pain is a feature of many cancers, particularly in the advanced stages at which the palliative care approach to symptom control achieves the best outcomes. The holistic approach generally dictates that any treatment of the cancer per se has symptom control as the primary objective at this advanced stage. Pain, which invariably increases with disease progression, is treated with opioids and adjuvant analgesic drugs together with physical therapies. Orally administered opioid drugs are used preferentially because of cost and convenience, but other routes of administration (subcutaneous, rectal, spinal) are also possible. More recently, transdermal fentanyl has been evaluated in the treatment of moderate to severe cancer pain. The rate of fentanyl absorption is constant (after a lag period), and the dose is altered by increasing or decreasing the area of skin covered by the patch (size and/or number of patches). The dosing interval for these systems is generally 3 days. The extent of pain relief provided by transdermal fentanyl and sustained release morphine formulations is similar, with quality-of-life instruments showing no consistent preference for either formulation. Open studies have suggested a lower risk of constipation. Transdermal fentanyl is effective in the treatment of severe cancer pain, particularly when the oral route is unavailable.

Lack of pain associated with microfabricated microneedles

Microscopic needles previously shown capable of transdermal delivery of drugs and proteins are demonstrated to be painless when pressed into the skin of human subjects.

Assessing the Impact of Heat on the Systemic Delivery of Fentanyl Through the Transdermal Fentanyl Delivery System

OBJECTIVES

To examine the effects of locally applied heat on the systemic delivery of fentanyl through the Transdermal Fentanyl Delivery System.

DESIGN

Open, 2-period crossover randomized study conducted in the anesthesia department of a university teaching hospital.

METHOD

Six healthy adult volunteers received a fentanyl 25-microg/h patch with and without local heat for 240 minutes followed by administration without heat for an additional 20 hours. Participants then crossed over. Venous blood was drawn at baseline and hourly for 24 hours. Peak plasma concentration (CMax) of fentanyl was measured and the area under the curve (AUC) of the plasma fentanyl concentration versus time post administration graph was evaluated.

RESULTS

Difference in CMax and AUC were not statistically significant over the entire 24-hour study period. However, for the 4-hour period of heat application statistically significant differences were seen in both mean CMax (heat, 0.4 ng/mL versus no heat, 0.1 ng/mL (P =.030)) and mean AUC (heat, 40 ng/mL x min versus no heat, 10 ng/mL x min (P =.010)).

CONCLUSION

Local heat can speed the onset of steady state fentanyl concentration in the Fentanyl Transdermal Drug Delivery System thus limiting the delay in onset of analgesia and allowing earlier identification and treatment of side effects.