Amikacin is an antibiotic typically used to treat very severe bacterial infections that have not responded to other antibiotics. It is an aminoglycoside antibiotic, a class of drugs that work by binding to proteins within bacteria and changing their shape, inhibiting the bacteria's ability to synthesize new proteins and reproduce. Amikacin is not absorbed very efficiently by the human body; over 90% exits the body unchanged within 24 hours, leaving only approximately 10% to actually bind with bacterial proteins and halt their development.
Amikacin treats a wide variety of bacterial infections. It is most effective against gram-negative bacteria, a group that does not hold the crystal violet stain used by microbiologists to differentiate bacteria when observing them with microscopes; this type of bacteria does not hold the stain due to the composition of their cell wall. Amikacin is only particularly effective against two non gram-negative bacteria, staphylococcus and nocardia (which can cause pneumonia and encephalitis).
Amikaicin was patented in 1971 and became commercially available in 1976. It is synthesized from kanamycin A, a similar antibiotic developed in 1957. Its patent has since expired, and it's now manufactured by several companies, including Teva Pharmaceuticals and Heritage Pharmaceuticals. Its trade names include Amikin and Amiglyde-V. The cost of amikacin treatment can vary widely, ranging from $13 to $130 for a month's supply in the developing world; a course of treatment typically costs $25 to 50 in the United States.
Amikacin is approved for use in both adults and children, but is not recommended for infants. Elderly patients should use it with caution.
Amikacin is also widely used in veterinary medicine; it only approved by the FDA for use in dogs and horses, but it has also been used to treat cats, rodents, cattle, birds, reptiles, amphibians, and fish. Animals treated with amikacin are vulnerable to many of the same side effects as humans, including kidney damage, hearing loss, and allergic reactions at the injection site; cats are particularly vulnerable to hearing damage from amikacin.
The World Health Organization has designated amikacin as an essential medicine, meaning it is regarded as thoroughly safe when used as directed and that it is considered critically important to public health. Many nations use the WHO's list as a basis for their medical infrastructure.
The most common side effects of amikacin are similar to other antibiotics: nausea and diarrhea, headache and lightheadedness, fatigue, sweating, and joint pain. These are rarely serious and typically subside after treatment is complete. However, amikacin can cause very serious side effects in some patients.
Like other aminoglycoside antibiotics, amikacin is mildly neurotoxic and nephrotoxic, i.e. damaging to the brain and kidneys. It has, in rare cases, caused significant damage to auditory hair cells, usually resulting in ringing in the ears or the loss of high-frequency hearing. One patient reported complete hearing loss after using amikacin for sixteen weeks, however this case was far from typical because the patient was both diabetic and suffering from late-stage kidney disease. In effecting the ear's hair cells, amikacin can also cause problems with balance, but this is also very rare. Hearing loss from amikacin is very uncommon and typically negligible, but patients who lose their hearing from the drug typically never recover it.
In addition to threatening hearing, amikacin can also, in rare cases, damage patients' nerves. Patients taking amikacin should contact their doctor immediately if they experience numbness, muscle twitching, or vertigo. The most serious cases of nerve damage with amikacin have involved seizures.
One trial suggested that nearly a quarter of patients using amikacin experienced a temporarily reduction in kidney function. An important test of renal health is the patient's serum creatinine, the amount of the compound creatinine in the blood. Creatinine is excreted by the muscles and removed by the kidneys; an unusually high amount of creatinine in the blood indicates that kidneys are not efficiently removing it. Many patients taking amikacin experience high serum creatinine levels, but they virtually always return to normal after stopping treatment. Most patients can handle this reduction in kidney function, and it is usually only acutely dangerous in patients with underlying kidney issues.
Patients should seek immediate medical attention if they have any symptoms of hearing loss, severe dizziness or trouble balancing, or kidney problems such as infrequent or painful urination. To mitigate the drug's most dangerous side effects, patients are often subjected to frequent blood or urine tests, as well as tests of kidney and nerve function and hearing exams.
As with all aminoglycoside drugs, amikacin should not be taken as a fixed dose; the dose should be determined primarily by the patient's body weight, and also consider their age, other medications, and the exact condition to be treated.
The typical dose of amikacin is between 15 and 22.5 milligrams per kilogram of the patient's body weight, divided into between one and three doses per day, depending on the severity of the infection. Most patients are initially given a maximum of one and a half grams per day, which may be adjusted following blood tests.
Certain conditions require significantly higher or lower doses; patients with urinary tract infections may be prescribed up to 250 milligrams, while patients with cystic fibrosis may only be prescribed 35 milligrams per kilogram.
Amikacin cannot be absorbed orally; it is typically taken intravenously or intramuscularly, i.e. injected directly into patient's blood stream or muscle tissue. It can also be taken through a nebulizer. Patients with infections of the central nervous system, such as meningitis, may need the drug to be injected intrathecally (directly into the spine) or intraventricularly (directly into their brain tissue).
Elderly and pediatric patients may need smaller doses of amikacin, because their kidneys are typically not as strong as those of younger and middle-aged adults. Amikacin usually stays in elderly patients' systems for much longer periods of time; one trial indicated that it clears twice as fast in twenty year old patients as for eighty year olds.
Patients with kidney problems may need to receive doses further apart depending on their creatinine clearance; these patients are unlikely to be prescribed the drug in the first place given its reputation for kidney complications, so this would be only in cases of last resort where other antibiotics have failed or pose an even greater risk.
Injection of amikacin is almost always done by a nurse or doctor; patients rarely prepare or inject the drug themselves, due to the specialized knowledge and equipment required at all steps. Since injection is so closely supervised, it's uncommon to miss the regularly scheduled doses, but in the event that a patient misses a dose it should be taken as soon as possible, and the remaining doses for the day should be taken at evenly spaced intervals.
Courses of amikacin typically last for seven to ten days; treatment periods longer than 14 days have not been carefully studied. Amikacin intake should always be closely measured and monitored, because taking too much can damage the brain and kidneys. Overdoses of amikacin can be very serious, and are usually treated with dialysis.
Amikacin's toll on the kidneys can be amplified if it's taken alongside certain other medicines, including chemotherapy, antivirals, intravenous antibiotics or osteoporosis medication, and even over the counter medicines for pain and arthritis, such as aspirin and acetaminophen.
Patients using amikacin should also avoid strong diuretics and drink plenty of fluids, in order to mitigate the drug's impact on their kidneys.
It is recommended that patients do not use amikacin concurrently with other drugs with neurotoxic or nephrotoxic effects, in order to avoid compounding these negative side effects. A wide variety of drugs have these effects, including bacitracin, cisplatin, cephaloridine, viomycin, colistin, and vancomycin. While these drugs are safe in their prescribed doses, mixing them with other drugs known to have neurotoxic or nephrotoxic properties could dangerously amplify these negative side effects.
Amikacin is known to be explicitly neurotoxic and nephrotoxic (damaging to the brain and kidneys). It is generally safe when used exactly as prescribed, but can be dangerous if taken in excess or for a prolonged amount of time, or by patients with existing kidney problems.
Amikacin can be particularly dangerous for patients with kidney problems; its most dangerous side effects, including hearing loss and nerve damage, are more common in people with preexisting renal problems.
Amikacin should never be taken while the patient is pregnant; it is thought to cause severe birth defects, including permanent deafness in the baby. This conclusion is in fact drawn from studies on a similar drug, streptomycin, as there have no been no thorough studies of amikacin in pregnant women. Trials examining rats and mice revealed no reproductive harm due to amikacin, but doctors nonetheless advise against the use of any aminoglycoside drug by pregnant women, based on the conclusion of the streptomycin study. Amikacin is partially secreted in breast milk, and thus should not be used by nursing mothers.
Amikacin has been known to cause severe allergic reactions in some users, so seek immediate medical attention if, after taking amikacin, you develop any symptoms of anaphylaxis, including itching, hives, shortness of breath, or swelling or the hands, face, or mouth. Amikacin contains a chemical called sodium metabisulfite which may be responsible for some patients' allergic response as it is known to cause anaphylaxis and asthma attacks in some individuals. Asthmatic individuals are known to be sensitive to sulfites, such as sodium metabisulfite, more often than non-asthmatic people, but sulfite sensitivity is very uncommon overall.
Patients with myasthenia gravis, an autoimmune disorder, should not use amikacin.
As with all antibiotics, amikacin should be used only to treat infections that are certainly caused by bacteria; careless use of antibiotics can reduce their effectiveness if users or diseases develop a tolerance for them.
Amikacin must be diluted before it can be taken; once diluted, the solutions must be refrigerated or frozen for long-term storage, but vials of unmixed amikacin can be stored at room temperature (68 to 77 degrees Fahrenheit, 20 to 25 degrees Celsius). It is sold in packs of ten vials, with three different sizes available: 100 mg per 2 mL (typically used only for pediatric patients), 500 mg per 2 mL, and 1000 mg per 4 mL.
Before it can be injected, amikacin must be mixed with a sterile diluent, such as dextrose or sodium chloride. The combined solution of amikacin and a diluent can be stored for up to several weeks at a time, but must be either refrigerated or frozen. Trials have shown that amikacin solutions will last for up to 24 hours at room temperature after 30 days frozen at -15 degrees Celsius, or 60 days refrigerated at 4 degrees Celsius. Amikacin should be removed from refrigeration at least one hour before use in order to warm to room temperature.
Amikacin is typically colorless, but may begin to turn pale yellow in storage; if this occurs, the medicine is still usable and has not lost potency. However, amikacin should be inspected for floating particles and unusual discoloration before use, and should not be used if either is present.
Amikacin should be kept out of the reach of children and pets.
For decades, amikacin has proven itself as a reliable antibiotic to use in dire situations when infections don't respond to milder treatment. In rare cases, its side effects can be extreme, but in bacterial infections serious enough to call for amikacin, the benefits outweigh the side effects. Its most dangerous side effects are very uncommon, and can largely be avoided by careful measurement of the medicine's dosage, proper preparation of diluted solution, and close monitoring of patients' kidney function. The World Health Organization's selection of amikacin for its list of essential medicines attests to the drug's safety, effectiveness and irreplaceability.