Can antibiotic drugs be administered faster and make acceptable serum concentrations if we give short but multiple infusions compared to long and fewer infusions? In this study we will compare giving meropenem 1 gram 6 times daily in 15 minutes infusions to the recommended 2 gram 3 times daily in 3 hours infusions. In patients in the intensive care unit, the need for intravenous access is of essence. If 6 short infusions results in the same serum concentrations as 3 long infusions, we will increase intravenous access from 15 to 22.5 hours daily.

The primary aim of this pilot study is to examine if the dosing of the antibiotic meropenem given as 1 gram 6 times daily in 15 minutes infusions can be compared to 2 grams given 3 times daily in 3 hours infusion when measuring the serum concentration above the minimum inhibitory concentration (MIC) ≥ 50 % of the time (2 mg/l).

The secondary aims are

• That both administration forms will result in serum concentrations above MIC ≥ 100 % of the time (2 mg/l)
• Days in hospital
• 30 days mortality after admittance to the ICU
• Serious side-effects

Five extra blood samples will be performed 24, 48 and 72 hours between two dosing intervals. The dose will be adjusted according to renal function which will be monitored daily. The patients will be supervised for adverse effects until 2 days after treatment has stopped.

The study will be performed from 2021 to the end of 2024.

Inclusion Criteria:

1. Patients ≥ 18 years admitted to the ICU at Oslo University Hospital, Rikshospitalet and
2. who shall be treated with meropenem because of proven or suspected serious infection and
3. who give their written informed consent either directly or through next of kin

Exclusion Criteria: Patients

1. with known hypersensistivity to betalactam antibiotics or
2. who use of valproat or
3. who are pregnant or
4. the lack of consent.