Colistin, a polymyxin antibiotic, is commercially available in two forms: colistin sulphate (oral or topical powder) and colistimethate sodium (CMS) (parenteral formulation) [1]. When used for neonatal multidrug resistance-gram-negative infections (e.g., carbapenem-resistant Acinetobacter, Klebsiella, and Pseudomonas), i.v. colistin is frequently effective (clinical response rate is 70.0%-90.0%) and is considered a last-resort option [2, 3]. However, pharmacokinetics in neonates differ from those in older children/adults. A number of pharmacokinetic studies suggest standard low doses may produce subtherapeutic plasma colistin concentrations. Some guidance recommends a loading dose strategy in neonates/infants [4-6]. The case studied is a 3.7 kg male post-emergency section term 38 weeks plus two days, 2025. An echo done and revealed a ventricular septal defect and a small left kidney medication start with ampicillin and cefotaxime as first-line prophylactic treatment in the Neonatal Intensive Care Unit (NICU), Algala Maternity Hospital, Tripoli, Libya. The subsequent medicines are described: Phenobarbitone for convulsion, and meropenem, amikacin as second line after C-reactive protein (CRP) was raised calcium gluconate 10.0% for hypocalcemia, furosemide and spironolactone for cardiac problem. Colistin was used in this stage because CRP raised again and there was no response to the third line of antibiotics [3, 7]. In the present case, the Clinical Pharmacists have the following issues regarding colistin use.