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Gentamicin

Gentamicin

Gentamicin has been recognised for many years, at least since 1989, as a very efficacious drug but one that has the potential to cause significant ototoxicity and nephrotoxicity when administered in inappropriate circumstances, doses or regimens. Some studies have estimated that the incidence of gentamicin ototoxicity is as high as 3%. Despite the well known hazards of this drug it has been and continues to be quite extensively used in Australian hospital settings.

What is Gentamicin?

Gentamicin is an aminoglycoside antibiotic. Other antibiotics in this family include tobramycin, streptomycin, neomycin, amikacin, and netilmicin. Such antibiotics derive their benefit by killing and preventing further growth of bacteria.

What is it used for?

It is generally used to treat serious bacterial infections. Gentamicin is active against a wide range of pathogenic gram-negative organisms and some gram-positive organisms such as staphylococcus.

When is it contraindicated?

Gentamicin should not usually be used if a person has had or has any of the following:

  • kidney disease or problems – gentamicin is excreted through the kidneys meaning the drug is in prolonged contact with renal tissue where a person has a degree of renal failure, which can cause damage to the renal tissue;
  • hearing problems;
  • Myasthenia gravis – gentamicin may aggravate muscle weakness; or
  • Parkinsons disease – gentamicin may aggravate muscle weakness.

Gentamicin may interact with other medicines, including:

  • some antibiotics;
  • diuretics;
  • cancer drugs such as cisplatin;
  • vitamin K; and
  • some muscle relaxants.

What are the potential side effects?

Gentamicin is potentially ototoxic and nephrotoxic. Ototoxic means potentially damaging to the ear, specifically the auditory nerve, cochlea or vestibular system. Nephrotoxic means potentially damaging to the kidneys.

People who experience gentamicin toxicity usually develop one or more of the following symptoms:

  • imbalance or ataxia (unsteady gait)
  • blurring of vision
  • deafness
  • oscillopsia (bouncing vision)

What is the usual dosing regimen?

The usual adult dose of gentamicin injection is 60-80mg per day for 7-10 days. It is usually administered intramuscularly. Gentamicin is also commonly administered intravenously, in which case the usual dose is 4-6mg/kg/day, which generally equates to a recommended daily dose of between 210mg and 350mg per 24 hour period.

It is generally accepted that in most circumstances, persons undergoing gentamicin therapy should be closely monitored for any signs of adverse reaction and the levels of gentamicin in their blood should be monitored regularly.

Are all instances where gentamicin is prescribed and an adverse outcome follows indicative of negligence?

No. Gentamicin is in some circumstances the drug of choice and even when administered at the correct dose over the correct period of time can cause adverse effects.

What are the important things to know in order to assess whether the administration of gentamicin was negligent?

Some things that may be relevant to determining the likelihood of a successful claim for compensation based on the inappropriate administration of gentamicin include:

  • what dose/s was administered;
  • how was the dose/s administered;
  • over what period of time was the dose administered;
  • was the person weighed prior to gentamicin being given;
  • was the person taking any other drugs, prescribed or over-the-counter;
  • did the person have any contraindications to gentamicin;
  • was the person warned of possible side-effects to gentamicin;
  • what side-effects resulted;
  • when did the side-effects occur; and
  • to what extent is the adverse reaction a continuing and disabling problem.

(A note of thanks to Ngaire Watson, Barrister, Culwalla Chambers, for her article “Gentamicin – An Antibiotic For Use With Care” which appeared in the June 2010 issue of Precedent, the Journal of the Australian Lawyers Alliance which has informed the discussion here).

How can Catherine Henry Lawyers help?

Our team of highly experienced health lawyers can assist you with expert advice and legal support on your options.

We are well known and highly respected in the health and medical litigation arena, with specialist knowledge accumulated over 20 years.

Catherine Henry has conducted numerous gentamicin toxicity cases with successful outcomes.

The following case study provides an examples of a case in which Catherine Henry successfully assisted an individual who have suffered gentamicin toxicity.

Case study

The plaintiff was admitted to hospital with lower abdominal pain, fever and spasms. Blood tests indicated she had a slightly elevated neutrophil count and a mild fever (both of which can be indicative of infection). A preliminary diagnosis of pancreatitis was made. After further testing she was diagnosed with a ruptured cyst or ruptured oesophagus. A definitive diagnosis was not made, however, the doctor ordered she be treated with intravenous Ampicillin, Flagyl and Gentamicin. The Ampicillin and Flagyl were commenced the same day.

The following day blood tests were done which showed a normal neutrophil count. The plaintiff showed no sign of fever. The Gentamicin that had been ordered the previous day to commence on the second day was administered despite the absence of any indication of infection.

Further testing two days later revealed multicystic disease affecting the kidneys and liver. The plaintiff had a long history of polycystic kidney and liver disease.

After three days of gentamicin therapy the plaintiff reported a feeling like mouth ulcers or blisters to the nursing staff. Despite stomatitis (an inflammation of the mucous lining of the mouth) being a side effect of gentamicin, no investigations were initiated.

Two days after being discharged from hospital, the plaintiff experienced difficulty with balance and complained of impaired vision and tinnitus (ringing in the ears). Two weeks later she lost a degree of hearing in both ears. After further investigation, a neurologist diagnosed her with permanent and irreparable damage to both ears as the result of Gentamicin administration.

The plaintiff sued the hospital alleging the hospital was negligent in commencing gentamicin when the drug was not clinically indicated, as at the time it was first given and on all subsequent occasions:

  1. there was no clear evidence of any serious infection; and
  2. any infection she may have had had responded appropriately to antibiotics already administered.

The hospital denied the administration of gentamicin was inappropriate. In particular, the hospital argued that triple antibiotic therapy (Ampicillin, Flagyl, and Gentamicin) was properly prescribed due to the possibility of a serious infection and the possibility of an extremely serious potential outcome.

The claim was resolved with a successful outcome for the plaintiff.

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