Analgesics Stronger than Asprin or Paracetamol

When pain fails to respond to aspirin or paracetamol [acetaminopen) and it is not possible to treat the underlying cause, more potent analgesics must be considered. There is little to choose between the opioids, codeine phosphate (30mg 1M or 10-60mg orally every 4-6 hours and ~ 200mg in 24 hours) and dihydrocodeine .tartrate (30mg every 4-6 hours or 50mg 1M or Sc). Dihydrocodeine is theoretically more potent, otherwise the 2 drugs have similar elimination half-lives and side effects e.g. respiratory depression, constipation, nausea and risk of dependence. Both drugs are widely prescribed in combination with aspirin or paracetamol although the doses of the opioids infixed-dose combined preparations are generally not adequate.

Dextropropoxyphene [propoxyphene) (65mg orally every 6-8 hours) and pentazocine (25-100mg every 3-4 hours) are other analgesics more potent than aspirin and paracetamol but the effect of oral doses of pentazocine is unreliable. Both have a greater number of side effects than codeine or dihydrocodeine. Combinations of dextropropoxyphene with aspirin or paracetamol are available but in both preparations the 2 constituents have very different half-lives.

The use of all these analgesics must be reviewed frequently. With the opioids, effects such as physical dependence should be measured against the benefits of pain relief and great care must be taken in patients with respiratory or hepatic disease. In patients in which respiratory depression is a potential problem, nefopam is a useful alternative. The drug does not cause respiratory depression, constipation or depengence but side effects do include insomnia, vomiting and dry mouth. Drug and Therapeutics Bulletin 22: 45 (28 Jun 1984)

4 INPHARMA® 14 Jul 1984 0156-2703/ 84/ 0714-0004/ 0$01 .00/ 0 @ ADIS Press