Evaluation of the accuracy of a pharmacokinetically-based patient-controlled analgesia system

Pharmacological Treatment of Cancer Pain: Alternative Routes of Opioid Administration

Cancer-related pain is present in 51% of patients at various stages of the disease, and the incidence increases up to 74% in advanced and terminal stages. The World Health Organization proposed and issued very simple guidelines for the pharmacologic treatment of cancer-related pain. According to the guidelines, opioid analgesics are the mainstay of analgesic therapy, and the first choice for drug administration is considered to be the oral route. However, in some clinical situations, the oral route is not feasible, and analgesic drugs consequently have to be administered via an alternative route. For example, this is the case when the patient presents vomiting, bowel obstruction, severe dysphagia, mental confusion and when the opioid dose has to be increased drastically in order to achieve adequate pain control. This review of the literature is aimed at describing the indications, the limits and the main aspects of the pharmacokinetics and pharmacodynamics relative to the alternative routes of administration of opioids most commonly used in clinical practice. Sublingual, rectal, subcutaneous, intravenous, transdermal and spinal administration routes are examined.

Recent developments in patient-controlled analgesia

Patient-controlled analgesia (PCA) has become the gold standard for acute pain management since it was first introduced 20 years ago, and its merits have been discussed in quite a large number of publications. This review summarizes the more recent developments, such as new application devices and strategies, including intranasal, spinal, and regional PCA; patient-controlled sedation; experience with children and elderly people; and some data from chronic pain situations. Analyzing PCA literature from 2001 onwards confirms the author's long belief that the PCA principle ("WYNIWYG": what you need is what you get) was the most important aspect of a patient-controlled strategy, more or less independent of the type of drug or machine. Discovering this principle has changed the understanding of pain and suffering.

Oral cavity complications of bone marrow transplantation

Bone marrow transplantation, once regarded as experimental, has evolved into a standard treatment for a variety of malignancies. Considerable advances have been made in histocompatibility typing, pretransplantation chemotherapy, and posttransplantation immunosuppressive therapy as well as prophylaxis and treatment of infections. Oral complications develop in almost all patients, and their early recognition may result in the institution of prompt treatment and prolonged survival. Mucositis, often severe and extremely painful, develops in more than three quarters of bone marrow transplant recipients, and its prevention, unfortunately, remains unsatisfactory. Herpes simplex virus and Candida albicans account for most oral infections, although their incidence has been dramatically reduced by the institution of prophylactic agents. Graft versus host disease continues to be a significant complication of marrow transplantation, and the detection of commonly occurring oral changes may support its diagnosis.

A pharmacokinetic approach to resolving spinal and systemic contributions to epidural alfentanil analgesia and side-effects

A pilot study was conducted in 7 normal volunteers to demonstrate the feasibility of employing pharmacokinetic tailoring to achieve matching plasma opioid concentration-time curves after epidural (e.p.) and intravenous (i.v.) alfentanil administration. Each subject participated in 1 pretest and 2 test sessions. Our pain model was cutaneous electrical stimulation of the finger and toe, adjusted to produce a baseline pain report of 5 (strong pain on a 0-5 scale). On test day 1, subjects received e.p. alfentanil (750 micrograms) and an i.v. saline infusion. Serial measurements of analgesia, end tidal CO2, pupil size, subjective side effects, and plasma alfentanil concentrations were conducted before and at various time intervals over a 4-h period after alfentanil administration. On test day 2, subjects received e.p. saline and a pharmacokinetically tailored i.v. infusion (using individual pharmacokinetics determined on the pretest day) designed to achieve a plasma concentration-time profile identical to that observed on the epidural day. The same battery of effect measurements was administered as on the 1st test day. Plasma alfentanil was measured to verify the accuracy of the tailored infusion. Plasma alfentanil concentration profiles were nearly identical on both test days. Peak plasma alfentanil concentrations were near the reported minimum effective analgesic concentration (MEAC). Overall, analgesia was slightly greater with e.p. administration. Onset of pain relief was rapid, and duration was approximately 1.5 h with e.p. and 1 h with i.v. alfentanil. There were no differences in pupil size, ETCO2, or subjective side effects between e.p. versus i.v. administration. We conclude that systemic redistribution from the epidural space appears to account for most, but not all, of the analgesia.

Overview of current development in patient-controlled analgesia

Over the past two decades, numerous trials have assessed the safety and efficacy of patient-controlled analgesia (PCA). Advantages over conventional parenteral narcotics reported from these trials include equivalent to superior pain relief, superior patient satisfaction, decreased sedation and anxiety, faster return to normal functional status, and reduction in nursing time and hospitalization. The majority of these trials have been conducted in the postoperative patient population. In the mid to late 1980s, interest arose in applying PCA technology to the management of cancer pain. Factors that served as an impetus for the use of PCA in cancer pain included favorable reports from the postoperative setting and the often-cited statistics regarding the magnitude of the cancer pain problem. Advances in PCA technology coupled with advances in vascular access technology that allow the placement of long-term ports and catheters to facilitate intravenous, epidural, or intrathecal administration of opioid analgesics have made the applicability of PCA in ambulatory cancer patients an attractive option. The greatest breakthrough in PCA technology came with the introduction of devices making it possible to choose between intermittent (demand bolus) and continuous administration (continuous infusion) or both intermittent and continuous modes. A comparison of these types of PCA devices is described. The limitations of the literature involving PCA therapy in cancer patients make it difficult to identify optimal patient selection criteria, PCA administration schedules, drug selection and dosing, and optimal route of administration. The current status and pertinent issues related to these topics are addressed.

Patient-controlled analgesic infusions: alfentanil versus morphine

Previously, we found that cancer patients using a pharmacokinetically based patient-controlled intravenous infusion system (PKPCA) to regulate their own morphine infusion rates achieved more relief from oral mucositis pain than similar patients using morphine by bolus-dose PCA. In this study, we employed the PKPCA system to compare efficacy and side-effect intensities of 2 mu-selective opioid analgesics, alfentanil and morphine, in bone marrow transplant (BMT) patients self-administering the drugs to relieve pain from oral mucositis. Patients using morphine by PKPCA obtained more pain relief than patients regulating their own alfentanil infusions during the first 4 days of continuous opioid infusion therapy. Side-effect intensities did not differ between the 2 study groups. In contrast to patients using morphine for 4-14 days, those receiving alfentanil by PKPCA required unexpectedly high plasma concentrations of the drug to obtain equivalent pain relief. Our results indicate that either the relative potencies of these 2 mu-selective opioids differ from previous estimates or analgesic tolerance developed to alfentanil but not to morphine. We conclude that alfentanil has similar efficacy in control of prolonged pain in BMT patients, but the utility of alfentanil in long-term pain management may be limited by relatively rapid tolerance onset.