On-call scenario 3: Resolution

Last updated: Wednesday, June 05, 2024

What an on-call pharmacist could advise...

As per the calculation above, you could advise the doctor that the product licence allows each 4.4g dose of IV co-trimoxazole to be diluted with 700mL glucose 5% in patients who are fluid restricted. 

However, this concentrated solution is less stable than the standard recommended dilution and has a higher risk of precipitation. It should therefore be administered over a maximum of 60 minutes and the drug inspected carefully throughout administration.

In addition, it means that the patient will still be receiving this volume four times per day which equates to nearly 3 litres which may be in excess of their fluid allowance. 

You check Medusa and this does give some unlicensed guidance where in patients who are severely fluid restricted, the drug may be given undiluted through a central venous access device over 90 to 120 minutes. Your patient only has peripheral venous access currently and inserting a central venous catheter is not without risk. 

Together you decide that the first dose which is due now be diluted in 700mL of 5% glucose and given peripherally, and that the patient be reviewed in the morning by the senior multi-disciplinary team.

Follow up

The next day you document your advice on the patient’s drug chart and speak to the ward pharmacist caring for the patient. They will  liaise with the team about the potential ways forward which include inserting central venous access, considering whether a switch from IV to oral co-trimoxazole might be clinically appropriate, or whether there is an alternative drug that may be used. 

They also signpost you towards the UKCPA Drug Dosing in Extremes of Body Weight guide, which discusses how to dose IV co-trimoxazole in patients who are obese. You review this document and share at your next on-call pharmacist group meeting.