Antibiotics - Polymyxins: Nursing pharmacology

Polymyxins are an older class of antibiotics, which are nowadays used as a last resort to treat bacterial infections when other antibiotics are either contraindicated or ineffective.

These medications affect susceptible gram-negative bacteria such as Escherichia coli, Pseudomonas aeruginosa, Klebsiella spp., and Shigella spp.

There are two approved medications in this class: polymyxin B and polymyxin E, also known as colistin. Both are available for intramuscular and intravenous use.

Additionally, polymyxin B can be given intrathecally, as an ophthalmic formulation, as well as by inhalation.Once administered, polymyxins work by binding to the bacterial membrane and disrupting it, which ultimately leads to bacterial cell death.Now, polymyxins can cause serious side effects like neurotoxicity and nephrotoxicity.

In fact, that’s a boxed warning for polymyxin B! Clients with neurotoxicity might experience facial flushing, drowsiness, dizziness, ataxia, and paresthesia.

Sometimes, neurotoxicity can cause respiratory paralysis. On the other hand, nephrotoxicity may present with a low urine output, albuminuria, cellular casts in the urine, and azotemia.

Finally, specific side effects associated with intravenous administration of polymyxins include fever, rash, and itching; while side effects of intrathecal polymyxin B use include headaches and neck stiffness.Regarding contraindications, polymyxins should not be used during pregnancy and breastfeeding, as their safety hasn't been established.

These medications should be used cautiously in elderly clients, as well as in those with neuromuscular disease like myasthenia gravis, and in clients with renal disease.

Finally, polymyxins should not be combined with other neurotoxic or nephrotoxic medications, such as aminoglycosides. And again, that’s a boxed warning for polymyxin B!

Also, polymyxins shouldn't be used with general anesthetics and neuromuscular blocking agents, such as succinylcholine, rocuronium, vecuronium, and atracurium, as they can increase the risk of respiratory paralysis.

Now, when a client is diagnosed with hospital-acquired pneumonia and is prescribed polymyxin B, first, perform a baseline assessment including weight, vital signs, SpO2, respiratory status, as well as their fluid intake and output.

Next, review recent laboratory test results, specifically CBC, renal function tests, urinalysis, culture and sensitivity results, and arterial blood gas analysis.

Lastly, review diagnostic test results, including chest X-ray or CT scan.Next, explain to your client that the medication will help to treat their pneumonia.

Let them know that you’ll first be administering a loading dose of the medication intravenously, followed by a dose every 12 hours.

Then, let your client know about important side effects, like neurotoxicity and nephrotoxicity; and reassure them you will be monitoring them closely to decrease the risk of these side effects.Okay, when preparing to administer polymyxin B intravenously, be sure your client is adequately hydrated, and that they have a patent IV and indwelling urinary catheter in place.

Then, confirm the correct dose by calculating units per kilogram of body weight, and input the correct mL/hr to be administered by infusion pump.

While your client is receiving the medication, be sure to monitor the insertion site closely for signs of extravasation, such as redness, puffiness, or blanching, and instruct your client to let you know if they feel any pain or tenderness.

Also, monitor their vital signs, and assess for neurotoxicity by instructing them to let you know if they experience drowsiness, dizziness, or paresthesias.

Lastly, be sure to monitor them for nephrotoxicity by keeping a close eye on their fluid intake and output, as well as their renal function tests.Finally, while caring for a client receiving polymyxin B, be sure to monitor for the development of side effects, and evaluate your client for the desired therapeutic response to the medication, including the resolution of their infection and absence of symptoms like fever and dyspnea.

All right as a quick recap… Polymyxins are a class of antibiotics used as a last resort to treat certain gram-negative bacterial infections.

These medications work by disrupting the bacterial cell membrane and causing cell death. Polymyxins can cause serious side effects like neurotoxicity and nephrotoxicity.

Nursing considerations when administering polymyxins include performing a baseline assessment, monitoring for signs of toxicity and side effects, and evaluating for the desired therapeutic response.

Client teaching is focused on what to expect during treatment and learning to recognize signs and symptoms that should be