This chapter deals mainly with the pharmacology of opioid analgesic agents. For more information on the clinical application of these drugs you might like to check out these other related chapters of the Virtual Anaesthesia Textbook:
The information (eg trade names and dosage schedules) supplied in some of these pages may be very specific to a particular country (for example Fiorinal contains completely different agents in the USA and Australia). Please keep this in mind and consult local information guides if in doubt.
The Hypermedia Assistant for Cancer Pain Management (HACPM - used to be called the Talarian Index) has an enormous amount of information pertaining to pain management including a table of equivalent doses for a substantial number of opioids with a second table for folks less than 50kg. They also have some general comments and cautions regarding the use of opioid analgesics.
I'll let this one speak for itself..."The Oxford Pain Internet Site is for anyone with a professional or personal interest in pain and analgesia. It is firmly based in the principles of evidence-based medicine and has pulled together systematic reviews with pain as an outcome." This is a fantastic resource including information on a large number of opioid and non-opioid analgesics. Well worth a visit.
Methadone, with its rapid onset and long duration, is enjoying something of a resurgence in interest.
The NZ Govt's MedsSafe Information for Health Professionals site provides monographs for most opioids - just enter the generic name in the search box. (Use pethidine to search for meperidine).
The Australian Medicines Handbook (AHM) and MIMS Online are resources delivered by subscription to many Australian university and health care organisations, for example via CIAP in New South Wales (passwords required).
RxMed still has a lot of drug monograph information free of charge. Drugs are listed only by trade name, unfortunately, and their search facility is not currently working.
Tramadol is a weak opioid action (about 1/10th the respiratory depression of morphine at equal doses) and inhibits noradrenaline and serotonin reuptake (like SSRI antidepressants). Monographs may be available via the links above. Compared to morphine, and when used for its opioid sparing actions, it may cause less constipation but more confusion. It can cause serious reactions, including seizures and dysphoric serotoninergic reactions, and interacts with a number of other drugs. IV boluses can cause acute hypertension and EEG activation during anaesthesia, and acute nausea post-operatively.
Questions about the Virtual Anaesthesia Textbook project itself should be e-mailed to Chris Thompson.