Am

Uses

Am is used for the short-term treatment of serious infections due to susceptible strains of Gram-negative bacteria. It is effective in bacterial septicemia (including neonatal sepsis); in serious infections of the respiratory tract, bones and joints, central nervous system (including meningitis) and skin and soft tissue; intra abdominal infections (including peritonitis); and in bums and post operative infections (including post-vascular surgery). Am is also effective in serious complicated and recurrent urinary tract infections due to susceptible Gram-negative organisms. It may be considered as initial therapy in suspected Gram-negative infections and therapy may be instituted before obtaining the results of susceptibility. Am is also effective in infections caused by Gentamycln and/or TobrAmykin resistant strains of Gram-negative organisms. Am has also been shown to be effective in Staphylococcal infection and may be considered as initial therapy under certain condition in the treatment of known suspected Staphylococcal disease such as, severe infections where the causative organism may either a Gram-negative bacterium or Staphylococcus infection due to susceptible strains of Staphylococcal I Gram-negative infections. In certain severe infections such as neonatal sepsis, concomitant therapy with a penicillin type drug may be used because of the possibility of infections due to Gram positive organism such as streptococci or pneumococci.

Am is also used to associated treatment for these conditions: Bacterial Peritonitis, Bacterial Sepsis, Bone and Joint Infections, Burns, Central Nervous System Infections, Endophthalmitis, Infection caused by staphylococci, Infective pulmonary exacerbation of cystic fibrosis, Intra-Abdominal Infections, Lung Infection, Meningitis, Bacterial, Mycobacterium avium complex infection, Neonatal Sepsis, Nosocomial Pneumonia, Postoperative Infections, Respiratory Tract Infection Bacterial, Skin and Subcutaneous Tissue Bacterial Infections, Tuberculosis (TB), Grade 1, grade 2, grade 3, grade 4 Urinary Tract Infection, Severe Bacterial Infections

How Am works

The primary mechanism of action of amikacin is the same as that for all aminoglycosides. It binds to bacterial 30S ribosomal subunits and interferes with mRNA binding and tRNA acceptor sites, interfering with bacterial growth. This leads to disruption of normal protein synthesis and production of non-functional or toxic peptides. Other actions have been postulated for drugs of this class. Am, as well as the rest of the aminoglycosides, are generally bacteriocidal against gram-positive and gram-negative bacteria.

Dosage

Am dosage

Adults and children: 15mg/kg/day in two equally- divided doses (equivalent to 500 mg bid in adults). Use of the 100 mg/2 ml strength is recommended for children for the accurate measurement of the appropriate dose.

Neonates and premature children: An initial loading dose of 10 mg/kg followed by 15 mg/kg/day in two equally divided doses.

Elderly: Doses should be adjusted under impaired renal function in elderly.

Life-threatening infections and/or those caused by pseudomonas: The adult dose may be increased to 500 mg every eight hours but should neither exceed 1.5 gm/day nor be administered for a period longer than 10 days. A maximum total adult dose of 15 gm should not be exceeded.

Urinary tract infections (Other than pseudomonal infections): 7.5 mg/kg/day in two equally divided doses (equivalent to 250 mg bid in adults).

Impaired renal function: In patient with impaired renal function the daily dose should be reduced and/or the intervals between doses increased to avoid accumulation of the drug. Simple doses schedule for renal impairment is given below:

Renal function Dosage schedule

Mild impairment 500 mg every 18 hours

Moderate impairment 500 mg every 24 hours

Severe impairment 250 mg every 24 hours.

Administration:

Intramuscular or intravenous administration: For most infections the intramuscular route is preferred, but in life threatening infections, or in patients in whom intramuscular injection route is not feasible the intravenous route may be used.

Intraperitoneal use: Am may be used as an irrigant after recovery from anesthesia in concentration of 0.25%.

Other routes of administration: Am in concentration of 0.25% may be used satisfactorily as an irrigating solution in abscess cavities, the pleural space, the peritoneum and the cerebral ventricles.

Intramuscular or intravenous administration: For most infections the intramuscular route is preferred, but in life threatening infections, or in patients in whom intramuscular injection route is not feasible the intravenous route may be used.

Intraperitoneal use: Am may be used as an irrigant after recovery from anesthesia in concentration of 0.25%.

Other routes of administration: Am in concentration of 0.25% may be used satisfactorily as an irrigating solution in abscess cavities, the pleural space, the peritoneum and the cerebral ventricles.

Side Effects

When the recommended precautions and dosages are followed the incidence of toxic reactous, such as tinnitus vertigo, and partial reversible or irreversible deafness, skin rash, drug fever, headache, paraesthesia, nausea and vomiting is low. Urinary signs of renal irritation, azotaemia and oliguria have been reported.

Toxicity

Oral (LD50): 6000 mg/kg (Mouse) . No antidote for toxicity is currently available. This drug is only 20% dialyzable; however, this is variable based on the type hemodialysis filter used.

Nephrotoxicity

Mild and reversible nephrotoxicity may be observed in 5 - 25% of patients. Am accumulates in the proximal renal tubular cells. Tubular cell regeneration occurs despite continued drug exposure. Toxicity most commonly occurs several days following initiation of therapy. Am may exacerbate pre-existing renal disease.

Ototoxicity

May cause irreversible ototoxicity. Ototoxicity appears to be correlated to cumulative exposure. Drug accumulation in the endolymph and perilymph of the inner ear causes irreversible damage to hair cells of the cochlea or summit of ampullar cristae in the vestibular complex. High- frequency hearing is lost first with progression leading to loss of low-frequency hearing. Further toxicity may lead to retrograde degeneration of the 8th cranial (vestibulocochlear) nerve. Vestibular toxicity may cause vertigo, nausea, vomiting, dizziness, and loss of balance.

Neuromuscular blockade

In addition to the above, amikacin may exacerbate neuromuscular blockade, however, this is less common.

Use in Pregnancy

Category D. Gentamicin and other aminoglycosides are known to cross the placenta. There is evidence of selective uptake of gentamicin by the fetal kidney resulting in damage to immature nephrons. Eighth cranial nerve damage has also been reported after in-utero exposure to some of the aminoglycosides. Because of the chemical similarity, all aminoglycosides should be considered potentially nephrotoxic and ototoxic to the developing fetus. Therapeutic blood amikacin levels in the mother do not equate with safety for the fetus. In reproductive toxicity studies in mice and rats, no effects on fertility or fetal toxicity were observed.

Use in Lactation

It is not known whether amikacin is excreted in breast milk. Since the possible harmful effect on the infant is not known, it is recommended that if nursing mothers must be given amikacin, the infants should not be breastfed during therapy.

Precaution

Since Am is present in high concentrations in the renal excretory system, patients should be well hydrated to minimize chemical irritation of the renal tubules. If azotemia increases, treatment should be stopped. Monitoring of renal function during treatment with aminoglycosides is particularly important.

Interaction

Concurrent administration of Am with myorelaxants leads to potentiation of their effects and there is a possibility of cessation of the breathing. The combination with other Aminoglycoside antibiotics should be avoided because of the augmentation of their ototoxic and nephrotoxic effects. Concurrent administration of Am with fast acting diuretics increases the risk of ototoxicity in patients with renal failure. Combination with Cephalosporins or Polymixins increases the risk of nephrotoxicity.

Food Interaction

Am Drug Interaction

Moderate: aspirin, aspirinUnknown: charcoal, charcoal, epinephrine, epinephrine, amoxicillin / clavulanate, amoxicillin / clavulanate, ciprofloxacin, ciprofloxacin, albuterol / ipratropium, albuterol / ipratropium, acetaminophen, acetaminophen, valproic acid, valproic acid, ascorbic acid, ascorbic acid, phytonadione, phytonadione

Am Disease Interaction

Major: dehydration, neuromuscular blockade, ototoxicity, renal dysfunction

Volume of Distribution

• 24 L (28% of body weight healthy adult subjects).

Following administration of usual dosages of amikacin, amikacin has been found in bone, heart, gallbladder, and lung tissue. Am is also distributed into bile, sputum, bronchial secretions, and interstitial, pleural, and synovial fluids.

Elimination Route

Rapidly absorbed after intramuscular administration. Rapid absorption occurs from the peritoneum and pleura. Poor oral and topical absorption. Poorly absorbed from bladder irrigations and intrathecal administration.

The bioavailability of this drug is expected to vary primarily from individual differences in nebulizer efficiency and airway pathology.

Following IM administration of a single dose of amikacin of 7.5 mg/kg in adults with normal renal function, peak plasma amikacin concentrations of 17-25 micrograms/mL are attained within 45 minutes to 2 hours.

Following IV infusion of the same dose given over 1 hour peak plasma concentrations of the drug average 38 micrograms/mL immediately following the infusion, 5.5 micrograms/mL at 4 hours, and 1.3 micrograms/mL at 8 hours.

Half Life

The plasma elimination half-life of amikacin is usually 2-3 hours in adults with normal renal function and is reported to range from 30-86 hours in adults with severe renal impairment.

Clearance

The mean serum clearance rate is about 100 mL/min and the renal clearance rate is 94 mL/min in subjects with normal renal function.

Elimination Route

This drug is eliminated by the kidneys. In adults with normal renal function, 94-98% of a single IM or IV dose of amikacin is excreted unchanged by glomerular filtration in the kidney within 24 hours. Am can be completely recovered within approximately 10-20 days in patients with normal, healthy renal function.

In patients with impaired renal function, the clearance of amikacin is found to be decreased; the more severe the impairment, the slower the clearance. The interval between doses of amikacin should be adjusted according to the level of renal impairment. Endogenous creatinine clearance rate and serum creatinine which have a high correlation with serum half-life of amikacin, may be used as a guide for dosing.

Pregnancy & Breastfeeding use

The safety of Am in pregnancy has not yet been established.

Contraindication

Am injection is contraindicated in patients with a known history of hypersensitivity to Am.

Special Warning

Impaired renal function: In patient with impaired renal function the daily dose should be reduced and/or the intervals between doses increased to avoid accumulation of the drug. Simple doses schedule for renal impairment is given below:

• Mild impairment: 500 mg every 18 hours
• Moderate impairment: 500 mg every 24 hours
• Severe impairment: 250 mg every 24 hours.

Pediatric Use: Safety and effectiveness of Am for injection in children or adolescents under 16 years have not been established

Acute Overdose

In the event of overdose or toxic reaction, peritoneal dialysis or hemodialysis will aid in the removal of Am from the blood.

Interaction with other Medicine

No information regarding drug interaction of Am is available.

Storage Condition

Store in a cool dry place protected from light. Keep out of reach of children.

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