Opioid drug effects

Reversal of opioid effects Complete or partial reversal of opioid drug effects, including respiratory depression, induced by either natural or synthetic opioids. Opioid overdose Management of known or suspected opioid overdose. 

Opioid drugs are often more effective than other nonnarcotic treatments, but they are also associated with more side effects making them less suitable for many patients. Higher doses which are more effective are also associated with undesirable effects such as sedation. 

Delta receptors are relatively selective for two related penta-peptides, methionine enkephalin and leucine enkephalin (met- and leu-enkephalin), which were isolated from porcine brain (Hughes 1975). Both met- and leu-enkephalin inhibit electrically induced contractions of guinea pig ileum, an effect that mimics those effects seen with opioid drugs, and is naloxone reversible. The enkephalins are processed posttranslational ly from proenkephalin, and secreted from central and peripheral neurons and endocrine cells in the adrenal medulla. 

Managing Opioid Side Effects and Drug Interactions... 

Mechanism of Action An opioid agonist that binds with opioid receptors in the CNS. Therapeutic Effect Alters the perception of and emotional response to pain reduces withdrawal symptoms from other opioid drugs. 

The previous edition of this book contained a detailed description of abuse of the antiemetic tablet preparation cyclizine by illicit drug users, nearly always crushed and injected along with methadone tablets or ampoules. Cyclizine is a constituent of Diconal along with the opioid dipipanone, and it seems that cyclizine has an opioid-enhancing effect which partly accounts for the particularly euphoriant property of Diconal. This could therefore be reproduced by combining cyclizine with the synthetic opioid methadone, and the intention to do this led to a wave of patients in the UK attempting to have their methadone prescribed in the ampoule or tablet form. 

Chiorphenamine is effective in reducing pruritus from opioid drugs and may have synergistic activity with other anti-emetic drugs, although it is not primarily used as an anti-emetic. 

Care should be taken not to administer any partial agonist or drug with mixed opioid receptor actions to patients receiving pure agonist drugs because of the unpredictability of both drugs effects reduction of analgesia or precipitation of an explosive abstinence syndrome may result. 

Shaham, Yavin. 1993. "Immobilization Stress-Induced Oral Opioid Self-Administration and Withdrawal in Rats Role of Conditioning Factors and the Effect of Stress on Relapse to Opioid Drugs." Psycfwpharmacotogy 111 477-85. 

The compulsive use of drugs for non-medical purpose. It is characterised by a craving for mood-altering drug effects, not painrelief. Addiction refers to a dysfunctional behaviour as opposed to the improved function and quality of life that result from pain relief. In cancer patients who use opioids for long-term pain relief addiction is extremely rare. 

Within the last 10, years several new compounds were launched in the field of non-steroidal antiinflammatory drugs (NSAIDs) with a clear focus on cyclooxygenase type 2 selective compounds. In the field of opioids on the other hand no new drugs have passed phase III clinical trials. In this field innovation has been achieved through new pharmaceutical formulations of known drugs such as transdermal systems, e.g. buprenorphine patch, transmucosal systems, e.g. fentanyl lollipop, or rectal delivery systems containing e.g. morphine. These were developed in order to reduce opioid side effects, but also to overcome pharmacokinetical limitations, in particular to prolong compliance and duration of action. 

Opioids basically exert their analgesic effects by inhibiting synaptic transmission in key pain pathways in the spinal cord and brain. This inhibitory effect is mediated by opioid receptors that are located on both presynaptic and postsynaptic membranes of pain-mediating synapses (Fig. 14—2). In the spinal cord, for example, receptors are located on the presynaptic terminals of primary (first-order) nociceptive afferents, and when bound by opioids, they directly decrease the release of pain-mediating transmitters such as substance P.35,38 Opioid drug-receptor interactions also take place on the postsynaptic membrane of the secondary afferent neuron—that is, the second-order nociceptive afferent neuron in the spinal cord.19,33 When stimulated, these receptors also inhibit pain transmission by hyperpolarizing the postsynaptic neuron.19... 

---