Compatibility of ropivacaine with morphine, sufentanil, fentanyl, or clonidine

Ropivacaine hydrochloride (HCl) ('Naropin') is a long-acting local anaesthetic agent, administered epidurally to patients undergoing various surgical procedures. A combination of local anaesthetic and opioid is often administered for the management of severe pain to ensure that a minimal dose of each is used. Ropivacaine might be used in combination with an alpha2-adrenergic agonist for the management of visceral pain. Stability data have shown that ropivacaine is compatible with the systemic narcotic opioid analgesics morphine sulphate, sufentanil citrate and fentanyl citrate for 14 days in a Polybag (AstraZeneca-AB, Sweden), but no data have been obtained for the longer-term compatibility of ropivacaine with these opioids or with the alpha2-adrenergic agonist clonidine HCl.

This study used the Mark II Polybag (AstraZeneca-AB, Sweden) to test the physical and chemical compatibility of these products for up to 30 days.

Ropivacaine HCl solution for epidural infusion, 2 mg/mL, in 200 mL Mark II Polybag and commercially available additives in glass ampoules or vials were used as starting material. Appropriate admixtures were made and their appearance, pH, and drug concentrations were monitored on days 0, 7, 14, and 30. The appearance of the admixtures was examined with the aid of a stereomicroscope (Olympus, no. 220186, New York, USA) at 10x magnification. Drug concentration and enantiomeric purity were determined using high-performance liquid chromatographic analysis.

All combinations at all doses stayed within the compatibility criteria (if no visible signs of physical changes in the admixture appeared throughout the 30 days of storage, and if pH and drug concentrations in each admixture did not vary by more than 10% between day 0 and days 7, 14, or 30 in storage). In addition, there were no important differences in the enantiomeric purity of ropivacaine with each combination.

The study demonstrated that ropivacaine was suitable for use in combination with the opioids morphine sulphate, sufentanil citrate, and fentanyl citrate, or with the alpha2-adrenergic agonist clonidine HCl, for up to 30 days of storage before the management of severe or visceral pain. From a microbiological point of view, combinations not prepared under aseptic conditions should be used immediately. 'Naropin' is a trade mark of the AstraZeneca group of companies.