Amphotericin B is a antibiotic and antimicottite drug with polyene structure of choice in systemic fungal infections such as for example in aspergillosis . Also used for its effectiveness in serious fungal infections.
It is an antibiotic that It is obtained by the fermentation of the bacteria Streptomyces nodosus . Its name, amphotericin, is because it is an amphipathic molecule, that is, it has a lipophilic and a lipophobic part. This is due to the presence of an acidic group and an amino group in their structure, which allows the product to be relatively soluble in water.
We will see the following characteristics of amphotericin B:
- Mechanism of action.
- Adverse reactions.
Mechanism of action
Amphotericin is a high-potency and broad-spectrum drug, that is, it is not specific to a type of microorganism, it can be effective against infections developed by different mushrooms .
As we have already commented, it is a molecule amphipathic . It is the lipophilic part, that is, the one that is soluble in water, the one that binds to the ergosterol molecules. This ergosterol is a molecule characteristic of the membranes of fungi.
Amphotericin presents a greater affinity for fungal membranes that for others, but even so, it also damages the membranes of human cells. Alters the permeability of sodium, potassium and hydrogen ions.
Is a fungicidal or fungistatic drug according to the sensitivity of the fungus and the concentration of drug that is administered. That it is fungicide means that it produces the death of the fungus. On the other hand, unlike the previous one, the fungostática activity inhibits the growth without producing the death.
This antibiotic is administered intravenously, and if this route is not possible, the spinal route is used. It could be administered orally, but it is absorbed badly and irregularly, producing, as a result, insufficient plasma concentrations.
The Maximum concentrations in plasma are observed at 2-3 hours after intravenous administration, without evidence of drug accumulation. It is administered by an intravenous infusion over 4 to 6 hours in order to minimize adverse effects.
On the other hand, amphotericin it binds in a high proportion to plasma proteins, Approximately 90-95%. That is why caution should be exercised in case you are taking medication with another drug that also binds to proteins. A co-administration of both can displace the amphotericin reaching toxicity.
The metabolism of this drug is not well known. A small amount is excreted in the bile and another by the kidney very slowly.
You can develop a a picture similar to the flu that runs with chills, fever, sickness and vomiting immediately after administration by intravenous infusion. They are mild or moderate symptoms that disappear during the first two days of treatment.
For these effects, it is usually accompanied by the administration of amphotericin B with NSAIDs, antiemetics, antihistamines or corticosteroids in order to reduce them and control them. Patients who are admitted to the hospital to be treated with amphotericin should be previously given a small dose to see their reaction to treatment.
In addition to these flu symptoms has other serious adverse reactions such as:
- Nephrotoxicity: manifesting itself with an increase in plasma creatinine and uric nitrogen. In addition, it presents with hypokalemia, hyponatremia and metabolic acidosis.
- Thrombophlebitis: To avoid these coagulation problems it is administered with corticoids and heparin.
As well can cause alopecia, bone pain , rash, anaphylactic reactions, bronchospasm and also the extravasation of amphotericin B can cause local irritation.
Amphotericin is a drug with which you have to be very careful since it is a drug that interacts with many other drugs. A nephrotoxic additive effect may be given when administered, at the same time, with aminoglycosides such as gentamicin, tobramycin or amikacin for example.
Must be reduce the dose of amphotericin B in the event of renal deterioration. With zidovudine, more serious myelotoxicity and nephrotoxicity have been observed when administered with amphotericin B.
As well Cyclosporine interacts with amphotericin. There is an increase in serum creatinine , although it could also be due only to high doses of ciclosporin.
On the other hand also can interact with drugs such as diuretics of the loop, cisplatin, corticoids or ACTH, showing hypocalcemia. Apart from those mentioned, there are many drugs that interact with amphotericin causing toxic effects in the patient.
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