Oral pentazocine

The Psychotomimetic Side Effects of Pentazocine

A literature review of psychotomimetic side effects associated with the use of pentazocine is presented. Clinical experience with pentazocine indicates a 1–2 percent occurrence of disturbing psychotomimetic side effects. Side effects noted include hallucinations, delusions, depression, distorted body images and depersonalization. These adverse effects occur more frequently with parenteral administration and appear to be dose-related. The most severe acute types of psychotic reactions tend to develop within two hours following a single administration. Usually the psychotic phenomenon is of a transitory nature, lasting from one to twenty-four hours. Acute symptoms such as hallucinations and distorted body images generally subside within hours, while depressive states may persist for one or more days. Treatment of the psychotomimetic effects may require only reassurance and discontinuation of pentazocine therapy. Benzodiazepines may be helpful in alleviating anxiety and reducing the effects of pentazocine.

Comparative effects and analgesic efficacy of the agonist-antagonist opioids

Pentazocine, butorphanol, nalbuphine, and buprenorphine are mixed agonist-antagonist opioids that are effective analgesics, with less abuse potential than the agonists morphine, propoxyphene, and codeine. The dual properties of the agonist-antagonists are largely explained by their varying actions at the postulated three types (mu, chi, and sigma) of opioid receptors. The agonist-antagonists are classified as either morphine-like or nalorphine-like, based on their acute effects and withdrawal symptoms after chronic dosing. Buprenorphine is morphine-like, while the other drugs are nalorphine-like. These agents vary in the duration of analgesia, with pentazocine having a mean action of three hours and buprenorphine greater than six hours. The hemodynamic effects of nalbuphine and buprenorphine generally resemble those of morphine, while pentazocine and butorphanol increase cardiac workload, blood pressure, and pulmonary artery pressure. The agonist-antagonists have ceilings for respiratory depression, whereas the agonists produce dose-dependent depression. Agonist-antagonists generally produce less increase in biliary ductal pressure than does morphine. The major clinical limitations are that agonist-dependent patients may experience unpleasant subjective effects, when treated with the agonist-antagonists, and the nalorphine-like agents can produce psychotomimetic effects. More clinical experience is needed to rank the abuse potential within this group of opioids. The newer agents are being studied for oral use in acute and chronic pain.

Adverse effects of commonly ordered oral narcotics

Approximately equianalgesic oral doses of codeine, an oxycodone compound resembling Percodan, and pentazocine were compared for adverse effects in a double-blind, randomized study of four doses of each drug given over two days to 247 postsurgical patients with pain. Placebo and parenteral morphine were also treated as negative and positive controls, respectively. Approximately 50 patients each received one of the five drugs. Codeine, pentazocine, and morphine had the same incidence of adverse effects (22 to 28 per cent). One capsule of oxycodone compound was the analgesic equivalent of 12.5 mg morphine with an adverse effect incidence of 4 per cent (placebo 8 per cent). Smoking made no difference in analgesic effect or adverse effects. Analgesics given in the evening intervening between the two days may have affected the analgesic performance of placebo.

Postoperative analgesia

Postoperative analgesia both by drugs and regional techniques is reviewed. In the United Kingdom in the last 25 years or more there has been little advance on either front. Some marginal improvement in regard to drugs might be brought about by better education of both doctors and nurses and better patient contact. Extradural analgesia and intercostal block do not offer a complete solution, though a judicious increase in the use certainly of the former might be beneficial. The problem awaits a radical new approach.

Analgesia following oral surgery for day patients: a clincial comparison of two analgesics

A single-blind, between-patient study was carried out in 167 patients following oral surgery to compare the effectiveness and tolerance of two combination analgesic preparations; pentazocine (15 mg) plus paracetamol (500 mg) and dextropropoxyphene hydrochloride (32.5 mg) plus paracetamol (325 mg). Assessments of pain and pain relief were made over two periods, initially over the 90 minute period following administration of either preparation and secondly, over the subsequent 3 days following discharge. At the hospital, those patients receiving pentazocine plus paracetamol achieved a greater relief of pain than those receiving dextropropoxyphene plus paracetamol, though the differences did not reach statistical significance. At home, pain relief was very similar for both groups of patients, both preparations being effective and well tolerated.