Ropivacaine, a new long acting amide type local anaesthetic, was compared with bupivacaine in a randomized double-blind study. One hundred and ten patients undergoing extradural anaesthesia received a test dose of 3 ml of 1% lignocaine with adrenaline which was followed by 15 ml of one of five solutions: 0.5, 0.75 or 1.0% ropivacaine or 0.5 or 0.75% bupivacaine. There was little difference between the groups with respect to speed of onset or sensory block. The duration of analgesia was increased by increasing the concentration of both drugs, but this had minimal effect on onset time or extent of block. When the same concentration of each drug was administered, there were inconsistent differences in duration of sensory block, none of which was statistically significant. Increasing concentration of both drugs resulted in greater degree and longer duration of motor block. Ropivacaine produced a slower onset, shorter duration and less intense motor block than the same concentration of bupivacaine. The cardiovascular changes were similar in all groups.

We have studied the effects of intrathecal injection of 0.5% bupivacaine in solutions containing different concentrations of glucose {0.33%, 0.83% and 8%) in three groups of 10 patients. The mean maximum extent of sensory block was significantly higher with 8% glucose (T3.6) than with 0.83% glucose {T7.2) or 0.33% glucose (T9.5). Administration of solutions containing 0.33% glucose produced a greater variability in upper level of sensory block (11 dermatomes) than the two other concentrations (six dermatomes each). The rate of onset of sensory block to T12 was fastest with solutions containing 8% glucose. Complete motor block of the legs was produced in every patient.

Ropivacaine 0.5%, 0.75% and 1.0% was investigated in an open study of extradural anaesthesia in three groups of 15 patients undergoing urological or orthopaedic surgery. Following a test dose of 3 ml of 1.0% lignocaine with 1:200,000 adrenaline, ropivacaine 20 ml was given in incremental doses over 4 min via a lumbar extradural catheter. The onset time for analgesia was short in all groups: T12 was blocked 4-6 min after the end of the injection of ropivacaine. The maximum segmental level was significantly higher in the 0.75% and the 1.0% groups (T2) than in the 0.5% group (T5). Complete motor block was obtained in seven, four and nine patients in the 0.5%, 0.75% and the 1.0% groups, respectively. Duration of analgesia increased with increasing concentration of ropivacaine: mean duration of analgesia was 203 and 266 min at T10 and 253 and 314 min at L5 for the 0.5 and 1% solutions, respectively. Mean duration of complete motor block was 94 and 192 min for the same solutions. Analgesia was satisfactory for surgery in all patients except for one in the 0.75% group. Hypotension was experienced by three, seven and three patients in the 0.5%, 0.75% and 1.0% groups, respectively. Bradycardia occurred in seven patients and was associated with hypotension in five. Backache was experienced after operation by four patients, and three patients complained of a brief mild headache. No late adverse events were seen.

We have studied the effects of intrathecal injection of 0.5% bupivacaine in solutions containing different concentrations of glucose (0.33%, 0.83% and 8%) in three groups of 10 patients. The mean maximum extent of sensory block was significantly higher with 8% glucose (T3.6) than with 0.83% glucose (T7.2) or 0.33% glucose (T9.5). Administration of solutions containing 0.33% glucose produced a greater variability in upper level of sensory block (11 dermatomes) than the two other concentrations (six dermatomes each). The rate of onset of sensory block to T12 was fastest with solutions containing 8% glucose. Complete motor block of the legs was produced in every patient.

SummaryThe efects of the gastric antisecretory drug, omeprazole. on the disposition of lignocaine were studied in 10 healthy male volunteers in a double-blind, randomised, placebo-controlled, two-period crossover trial. Omeprazole 40 mg or placebo was taken daily for one week before administration of lignocaine I mg.kg-' (3.7 pmol.kg-') given intravenously over 10 min. Venous concentrations of lignocaine and its metabolite monoethylglycinexylidine were measured in plasma with reversed phase liquid chromatography. The mean (95% CI) areas under the curve at infinity for lignocaine after pretreatment with omeprazole or placebo were 6.67 (4.9043.45) pmol.h.1-' and 6.14 (5.05-7.23) pmol.h.l-', respectively ( p = 0.44). The respective areas for monoethylglycinexylidine were 1.85 (1.25-2.45) pmol.h.l-' and 1.79 (1.44-2.14) pmol.h.1-' ( p = 0.78). Similarly, omeprazole had no signijcant effect on the half-lives of lignocaine or methylglycinexylidine. Key wordsAnaesthetic, local; lignocaine. Pharmacokinetics. Pharmacology; omeprazoleOmeprazole is an antisecretory drug which inhibits K + , H+-ATP-ase in the gastric parietal cell resulting in long lasting reduction of gastric acid secretion [ 11. This drug has been shown to be effective in reducing acidity and volume of gastric contents in various situations and could prove useful as prophylaxis against the acid pulmonary aspiration syndrome and against stress-induced gastric ulceration or haemorrhage in at-risk patients [24].The H, receptor antagonists, cimetidine and ranitidine, have been shown to reduce hepatic clearance of lignocaine and other amide local anaesthetics [5-7l, although in the case of ranitidine this has not been a consistent finding [8].Omeprazole, in common with the H, receptor antagonists, has inhibitory effects on the hepatic microsomal cytochrome P450 system and may reduce the clearance of certain co-administered drugs [9]. Lignocaine, a drug with a narrow therapeutic range, may be administered in high doses concurrently with gastric antisecretory drugs to obstetric and critical care patients for nerve block or as an anti-arrhythmic. This study was designed to investigate a possible pharmacokinetic interaction between lignocaine and omeprazole. MethodsTen healthy male volunteers took part in a double-blind, placebo-controlled, two-period crossover study. With Ethics Committee approval, omeprazole (40 mg) or placebo was taken by mouth each morning for the 7 days preceding the study day and 1 h before intravenous lignocaine infusion on the morning of the study day. After arrival in the study room, the subjects took the test medication with 200 ml water and rested in a chair for 1 h before the infusion of lignocaine began. At that point they lay supine for baseline ECG and arterial blood pressure measurements and remained thus during the infusion. A minimum of 15 days elapsed between the two crossover phases whose order was by random allocation.On the study day, lignocaine hydrochloride (1 mg.kg-', 3.7 pmol.kg-') was infused intravenously over