Opioid-Induced Constipation in Real-World Practice: A Physician Survey, 1 Year Later

Iatrogenic Side Effects of Pain Therapies

Pain regimens, particularly for chronic cancer and noncancer pain, must balance the important analgesic benefits against potential risks. Many effective and frequently used pain control regimens are associated with iatrogenic adverse events. Interventional procedures can be associated with nerve injuries, vascular injuries, trauma to the spinal cord, and epidural abscesses. Although rare, these adverse events are potentially catastrophic. Pharmacologic remedies for pain must also consider potential side effects that can occur even at therapeutic doses of over-the-counter remedies such as paracetamol (acetaminophen) or nonsteroidal anti-inflammatory drugs. Opioids are effective pain relievers but are associated with many side effects, some of which can be treatment limiting. A prevalent and distressing side effect of opioid therapy is constipation. Opioid-induced constipation is caused by binding to opioid receptors in the gastrointestinal system, making conventional laxatives ineffective. Peripherally acting mu-opioid receptor antagonists are a new drug class that offers the benefits of preserving opioid analgesia without side effects in the gastrointestinal system. An important safety concern, particularly among geriatric patients is the increasingly prevalent condition of polypharmacy. Many senior patients take five or more medications, including some that may be contraindicated in geriatric patients, duplicative of other drugs, have potential pharmacokinetic drug-drug interactions, or may not be the optimal choice for the patient's age and condition. Careful assessment of medications in the elderly, including possibly deprescribing with tapering of certain drugs, may be warranted but should be done systematically and under clinical supervision.

Adherence to coprescribing of laxatives with opioids and associated characteristics in general practices in the Netherlands

BACKGROUND

Guidelines recommend to prescribe a laxative with an opioid to prevent constipation. We aimed to determine the adherence by general practitioners (GPs) to this recommendation and to explore which GP- and patient related factors were associated with it from the perspective of the GP.  METHODS: We conducted an observational study using GPs' prescription data from the Nivel Primary Care Database combined with a questionnaire asking for reasons of non-adherence. The proportion of first opioid prescriptions prescribed together with a laxative was determined as primary outcome. Possible explanatory factors such as the quality of registration, the level of collaboration with the pharmacy, familiarity with the recommendation and use of a clinical decision support system were explored, as were the self-reported reasons for non-adherence (classified as either GP-related or patient-related). We assessed the association of factors with the primary outcome using univariable multilevel logistic regression analysis.

RESULTS

The recommendation was measured in 195 general practices. The median proportion of first opioid prescriptions prescribed together with a laxative in these practices was 54% (practice range 18-88%). None of the determinants was consistently associated with the primary outcome. GPs from 211 practices filled out the questionnaire and the most frequently mentioned reason not to prescribe a laxative was that the patient has laxatives in stock, followed by that the patient doesn't want a laxative; both were patient-related factors.

CONCLUSION

There was room for improvement in following the guideline on laxative prescribing in opioid use. A main reason seemed to be that the patient refuses a laxative. Improvement measures should therefore focus on communication between GPs and patients on the relevance of co-using a laxative with opioids. Future studies need to establish the effect of such improvement measures, and determine whether reasons for non-adherence to the guideline changed over time.

The Impact of P-Glycoprotein on Opioid Analgesics: What's the Real Meaning in Pain Management and Palliative Care?

Opioids are widely used in cancer and non-cancer pain management. However, many transporters at the blood-brain barrier (BBB), such as P-glycoprotein (P-gp, ABCB1/MDR1), may impair their delivery to the brain, thus leading to opioid tolerance. Nonetheless, opioids may regulate P-gp expression, thus altering the transport of other compounds, namely chemotherapeutic agents, resulting in pharmacoresistance. Other kinds of painkillers (e.g., acetaminophen, dexamethasone) and adjuvant drugs used for neuropathic pain may act as P-gp substrates and modulate its expression, thus making pain management challenging. Inflammatory conditions are also believed to upregulate P-gp. The role of P-gp in drug-drug interactions is currently under investigation, since many P-gp substrates may also act as substrates for the cytochrome P450 enzymes, which metabolize a wide range of xenobiotics and endobiotics. Genetic variability of the ABCB1/MDR1 gene may be accountable for inter-individual variation in opioid-induced analgesia. P-gp also plays a role in the management of opioid-induced adverse effects, such as constipation. Peripherally acting mu-opioid receptors antagonists (PAMORAs), such as naloxegol and naldemedine, are substrates of P-gp, which prevent their penetration in the central nervous system. In our review, we explore the interactions between P-gp and opioidergic drugs, with their implications in clinical practice.