Amikin

Amikin belongs to the class of medicines known as aminoglycoside antibiotics which is used to treat serious bacterial infections in many different parts of the body. This medicine is for short-term use only ranging from 7 to 10 days. It works by killing bacteria or preventing their growth. However, this medicine will not work for colds, flu, or other viral infections.

Amikacin is used widely in clinical practices to treat tuberculosis, complicated and recurrent urinary tract infections, severe gram-negative infections, bacterial septicemia, infections of respiratory tract, intra-abdominal infections, peritonitis, postoperative infections, meningitis, neonatal sepsis, burns etc.

It is also recommended as a reserve drug for hospital acquired gram-negative bacillary infections where gentamicin/tobramycin resistance is high.

If you are about to start Amikin, the risks and benefits ratio of taking this medicine should be considered. This is a decision that your doctor will make with your active participation.

For this medicine, certain factors such as present and past illness, drug interactions, metabolic impairments, hypersensitivity reactions, pregnancy, lactation etc. should be considered as they may alter the drug action. Thus, the use of aminocaproic acid should be considered cautiously.

Amikacin is a semisynthetic derivative of kanamycin to which it resembles in pharmacokinetics, dose and toxicity. The outstanding feature of amikacin is its resistance to bacterial aminoglycoside inactivating enzymes. Thus, it has the widest spectrum of activity, including many organisms resistant to other aminoglycosides.

However, relatively higher doses are needed for pseudomonas, proteus, and staph. infections. The aminoglycoside antibiotic like amikacin is bactericidal having the same general pattern of action which may be described in two main steps:

• Transport of aminoglycoside through the bacterial cell wall and cytoplasmic membrane.
• Binding to 30S ribosomal subunits of susceptible bacteria resulting in inhibition of protein synthesis.

Resistance to aminoglycosides (e.g. Amikacin) is acquired by one of the following mechanisms:

• Mutation decreasing the affinity of ribosomal proteins that normally bind the aminoglycoside.
• Decreased efficiency of the aminoglycoside transporting mechanism.

Medicines should be used following the directions given by a doctor. The dose of Amikin will vary according to patient’s condition or requirements. You should follow the doctor's directions and advice. The amount of medicine that you take should not exceed the maximum therapeutic dose.

Also, the frequency of your daily drug administration and the duration of drug therapy depend on the particular medical problem for which you are taking the medicine.

Parenteral administration of amikacin is described below:

• Uncomplicated urinary tract infections: 250 mg amikacin is given in adults twice a day or via IV injection over 2-3 minutes or as IV infusion.

• Severe gram-negative infections resistant to gentamicin and tobramycin: 15 mg/kg daily in equally divided doses is injected in an adult at every 8 or 12 hours for 7-10 days. Up to 500 mg amikacin can be given 8 hourly in life-threatening infections. 

• Child: 15 mg/kg daily in equally divided doses is injected at every 8 or 12 hours for 7-10 days. 

• Neonates: 10 mg/kg daily in 2 divided doses.

• Impaired renal function: in patients with impaired renal function the daily dose should be given cautiously. The intervals between doses can be increased to avoid accumulation of the drug. Simple (renal function) doses schedule for renal impairment is given below:
  •   Mild impairment: 500 mg every 8 hours
  •   Moderate impairment: 500 mg every 24 hours
  •   Severe impairment : 250 mg every 24 hours

Always try to take your medicine in time. If you miss any dose of this medicine, you should take it as soon as possible. But when it is time for your next dose, then skip the missed dose and go back to your regular dosing schedule.

You should store the medicine in a closed container at room temperature away from heat, moisture, and direct light. 

Regular visits are recommended to make sure this drug is working properly or not.

Before starting Amikin therapy, you should know about some important guidelines which are enlisted below:

• Safety has not been established for treatment period > 14 days. Monitoring of renal function is recommended before and during treatment with amikacin. Cautious use in patients past middle age and in those with kidney damage.

• If signs of ototoxicity, neurotoxicity, or hypersensitivity occur, you should discontinue receiving Amikacin immediately.

• It is effective in tuberculosis, but rarely used for this purpose. More hearing loss than vestibular disturbance occurs in toxicity.

• Potentially fatal conditions may also occur due to increased ototoxic and nephrotoxic effects with other nephrotoxic or ototoxic drugs.

• Contraindicated in pregnancy, lactation, perforated ear drum, myasthenia gravis, and known hypersensitivity to amikacin or its constituents.

• Avoid aminoglycosides during pregnancy due to risk of fetal toxicity. There is positive evidence of human fetal risk based on adverse reaction data from investigational or marketing experience or studies in humans.

• Avoid concurrent use of other ototoxic drugs, e.g. high ceiling diuretics, minocycline etc.

• Avoid concurrent use of other nephrotoxic drugs, e.g. amphotericin B, vancomycin, cyclosporine and cisplatin. Amphotericin B may lead to increased nephrotoxicity and reduced clearance of Amikacin when used together. 

• Cautious use of muscle relaxants in patients receiving an aminoglycoside (e.g. amikacin).

• Do not mix aminoglycide with any drug in the same syringe or infusion bottle.

There are some unwanted side-effects associated with Amikin that usually do not need medical attention. These side-effects usually go away during the treatment episode as your body adjusts to the medicine. Additionally, your health care professional may advise you about the ways to prevent or reduce those unwanted side-effects.

Sometimes, you may need to consult with the doctor if you feel any of these toxic effects which are common to all members, but the relative propensity differs:

• Ototoxicity: this is the most important dose and duration of treatment related adverse effect. The vestibular or the cochlear part may be primarily affected by a particular aminoglycoside (e.g. amikacin). These drugs are concentrated in the labyrinthine fluid and are slowly removed from it when the plasma concentration falls. Ototoxicity is greater when plasma concentration of the drug is persistently high and above a threshold value.

• Nephrotoxicity: it manifests as tubular damage resulting in loss of urinary concentrating power, low GFR, nitrogen retention, albuminuria and casts. Amikacin attains high concentration in the renal cortex and toxicity is related to the total amount of the drug received by the patient. Essentially, renal damage caused by amikacin is totally reversible, provided the drug is promptly discontinued. This incidence is more in elderly and in those with preexisting kidney disease.

• Neuromuscular blockade: all aminoglycosides including amikacin reduce Ach release from the motor nerve endings and interfere with mobilization of centrally located synaptic vesicles to fuse with the terminal membrane as well as decrease the sensitivity of the muscle end-plates to Ach. Myasthenic weakness is accentuated by Amikacin.