Analgesics opioids paracetamol

The second group of non-opioid analgesics, which are not classified as NSAIDs, consists of substances that lack anti-inflammatory properties, such as phenazones, metamizole (dipyrone) and paracetamol. Their molecules are neutral or weakly basic, have no hydrophilic... 

Co-codamol is a combination of paracetamol (nonnapioid analgesic) and codeine (opioid analgesic). One of the side-effects of opioids is constipation. Naprosyn is a proprietary (trade name) preparation of the non-steroidal antiinflammatory drug naproxen Adalat is a proprietary preparation of the calcium-channel blocker nifedipine Amoxil is a proprietary preparation of the beta-lactam amoxicillin and Dulco-lax is the brand name of the stimulant laxative bisacodyl. 

Alternative products to diclofenac include naproxen and mefenamic acid, both of which are non-steroidal anti-inflammatory drugs. Co-codamol is a mixture of the opioid analgesic codeine and paracetamol and it does not possess the anti-inflammatory component. It may be used in pain management either where NSAIDs are contraindicated or in patients who are intolerant to the effects of NSAIDs. 

Codeine, one of the principal alkaloids of opium, has an analgesic efficacy much lower than other opioids, due to an extremely low affinity for opioid receptors. It is approximately one-sixth as potent as morphine. It has a low abuse potential. In contrast to other opioids, with the exception of oxycodone, codeine is relatively more effective when administered orally than parenterally. This is due to methylation at the C3 site on the phenyl ring (Figure 7.3), which may protect it from conjugating enzymes. It is used in the management of mild-to-moderate pain, often in combination with non-opioid analgesics, such as aspirin or paracetamol. It is valuable as an antitussive and for the treatment of diarrhoea. Side effects are uncommon and respiratory depression, even with large doses, is seldom a problem. 

Clinical use Paracetamol (Ameer and Greenblatt, 1977 Clissold, 1986) has analgesic and antipyretic properties, but no relevant anti-inflammatory action. It is used for the treatment of various mild to moderate pain conditions and to reduce fever. Paracetamol is one of the most popular analgesics as a single drug or in multi-ingredient preparations, often in combination with NSAIDs or weak opioids. 

Analgesic efficacy and clinical use Dextropropoxyphene (Grover, 1988) is a moderately potent opioid analgesic often combined with paracetamol or acetylsalicylic acid or other NSAIDs (Collins et al., 2000). As the hydrochloride or napsylate it is used orally for the treatment of mild, moderate, or severe pain (Beaver, 1984). 

Paracetamol and opioid analgesics are safe to use in porphyria, however diclofenac is one of the drugs known to be unsafe to prescribe in porphyria. There are other NSAIDs such as ibuprofen or naproxen which are not listed as unsafe and the medical team should be advised to amend the prescription accordingly. However if Mrs JC is in severe pain it may be necessary to prescribe a strong opiate. These are safe in porphyria. 

Paracetamol is considered to be first-line treatment for osteoarthritis. It should be taken regularly. Paracetamol is the initial drug of choice because there is only a small inflammatory component to osteoarthritis and paracetamol is usually effective in the early stages of the disease. Compound analgesics like co-codamol may be used although their benefit over paracetamol alone is small and the opioid component may lead to unwanted side-effects. 

This chapter concentrates on some drug choices in acute rather than chronic pain, but the same principles can be used to determine the appropriateness of other types of analgesic. The drugs considered in this section are paracetamol, non-steroidal anti-inflammatories (NSAIDs specifically diclofenac, ibuprofen, indometacin, naproxen, sulindac and tenoxicam) and opioids (codeine, dihydrocodeine, morphine, pethidine and tramadol). Unless otherwise stated, all pharmacokinetic data originate from standard reference sources [1-5] and apply to adults only. 

In theory, ibuprofen and aspirin are the most effective analgesics as they act at the site of the pain, rather than centrally, in the manner of paracetamol and opioids. 

Acetaminophen, also known as paracetamol in other countries, is available widely without prescription as an analgesic and antipyretic. It is available in various oral dosage forms, including an extended-release preparation. Acetaminophen may be combined with other drugs, such as antihistamines or opioid analgesics, and marketed in cough and cold preparations, menstrual remedies, and allergy products. 

The drugs dealt with in this section include aspirin and other salicylates, NSAIDs, opioid analgesics, and the miscellaneous analgesics, such as nefopam and paracetamol. Table 6.1 , (p.l34) contains a listing, with a further classification of the NSAIDs. 

A placebo-controlled, crossover study in 26 healthy subjects found that both intravenous granisetron 3 mg and tropisetron 5 mg blocked the analgesic effect of a single 1 oral dose of paracetamol given 90 minutes later. The pharmacokinetics of paracetamol were unaffected by the two drugs. The interaction was thought to involve the serotonergic system, see Mechanism, in Opioids + Antiemetics Ondansetron , p.l61. 

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