1. Overview in short 

Colistimethate is used as an injection for treatment of bacterial infections. It is a bactericidal antibiotic. It can be used as liquid or as an intravenously administered injection. It can be used as an intramuscular injection. It can also be used as a nebulizer for treating respiratory infections. It is widely used against gram negative infections and other serious infections. It is also a polymyxin antibiotic agent.  Colistin is also known as colistimethate and polymyxin are different in their mode of actions and hence need not be confused as the same antibiotics. Colistin is considered a last resort drug for treating multidrug resistant bacterial infections. Colistimethate is eliminated by the kidneys mainly, as well by non renal pathways. 

2. Use of colistin specific to kidneys

Colistin is considered as nephrotoxic and the toxic effect it exerts on the kidney is deemed reversible. Colistin is also known to exacerbate renal impairment. Colistin can be cleared during the process of haemodialysis. There is no other mechanism for returning colistin from dialysate post dialysis back to the blood. Drug manufacturers are suggestive of the fact a standard dose of colistin of about 9 million units per day can be used for patients with normal renal function and who are on continuous renal replacement therapy. This dose is significantly reduced in patients with renal impairment (5.5-7.5 MU/ day) dose is recommended in patients with creatinine clearance less than 50ml/min and 4.5-5.5 MU/day when the creatinine clearance is less than 30ml/min and 3.5 MU/da with creatinine clearance less than 10ml/min. Several research data are suggestive of the fact that several hyper absorptive filters can efficiently adsorb colistin and a bit higher doses would be required 13.5 instead of 9 MU/day. 

3. Dose in general population IV: 

Adults and adolescents- The recommended dose is 9MIU/day and is divided into 2-3 doses per day. A maintenance dose of up to 12 MIU/day is recommended for patients with good renal function. The safety quotient of the drug is still in question. Dose reductions are advised to patients having renal dysfunction. 

4. Dose especially mention in kidney disease and in dialysis patients

For children below 12 years, colistin is not at all recommended owing to the questionable safety and efficacy of the drug. The drug can be intravenously or intramuscularly injected at 2.5-5mg/kg/day. The frequency of administering the injection is every 6 to 12 hours. 

5. Side effects especially on kidneys 

Colisthemate are very nephrotoxic due to their narrow therapeutic index. Colisthemate builds up in the body and causes programmed cell death, also known as apoptosis. This causes renal failure as well as significant histopathology and tissue damage. Increased exposure to Colisthemate generated dilatation in renal tubules, resulting in tissue scarring and necrosis in a time and dose dependent manner, according to several research findings. Acute renal injury is one of the most serious side effects of colistin. (AKI). Such occurrences are associated with a poor prognosis and a higher probability of patient mortality. Patients with AKI who were given polymyxin treatment had a higher rate of Acute kidney injury (AKI). Increased age and weight have been linked to an increased risk of AKI, with the effect being dosage independent. These are perhaps unchangeable factors. There are a number of controllable factors, such as the usage of nephrotoxic medicines. Non-steroidal anti-inflammatory medications and calcineurin inhibitors have been identified as modifiable risk factors. Co-administration of antibiotics such as vancomycin, aminoglycosides, and rifampin with colistin has been shown to enhance the risk of nephrotoxicity in CKD patients.

6. Only major drug interactions 

Colistin is known to interact with other antibiotics like amphotericin B, bacitracin, it moderately interacts with other drugs amikacin, acyclovir, cisplatin, cyclosporine which are immunosuppressive drugs given to patients with renal dysfunction.One of the major contradiction of the drug is hypersensitivity. Colymycin can be an alternative  if one is allergic to colistin. 

7. Brands available in India

Conclusion: 

The antibacterial medication Colistin has been highlighted in this paper. This medication is typically used to treat multidrug-resistant bacterial infections as well as people with renal failure. This medication has a high risk of causing renal damage. If blood urea nitrogen or creatinine level is elevated then the use of colistin can be avoided. This is essentially a last-resort medication. These drugs can also interact with other medications, increasing the risk of kidney injury.  Colistin is not indicated for patients with renal impairment or dialysis, according to current guidelines, due to its narrow therapeutic index.  Colistin should be used in minimal doses by people with renal impairment.