Tobramycin is an antibiotic belonging to the class of aminoglycosides which derives from the fermentation of Streptomyces tenebrarius .
Tobramicina - Chemical Structure
Tobramycin is available in different pharmaceutical formulations, including nebulising solution, inhalation powder, eye drops, ophthalmic ointment and solution for intramuscular or intravenous administration.
Indications
For what it uses
The use of tobramycin is indicated for the treatment of:
- Urinary tract infections (parenteral administration);
- Septicemia (parenteral administration);
- Bone infections (parenteral administration);
- Skin and soft tissue infections (parenteral administration);
- Infections of the gastrointestinal tract (parenteral administration);
- Meningitis (parenteral administration);
- Infections of the bronchi and lungs (parenteral administration);
- Infections of the eye and ocular adnexa (ocular administration);
- Lung infections caused by bacteria belonging to the genus Pseudomonas, including infections caused by Pseudomonas aeruginosa (inhaled administration).
Furthermore, parenteral tobramycin can be used as a second-choice drug in the treatment of infections with Escherichia coli and staphylococci.
Warnings
Tobramycin is ototoxic and nephrotoxic (respectively, toxic to the ear and to the kidneys), therefore, before starting treatment with the drug and for the duration of the drug, regular checks of renal function and hearing should be performed .
When tobramycin is administered parenterally, the blood concentrations of the same should be regularly monitored, so as not to reach too high levels of the drug that could facilitate the occurrence of ototoxicity and / or nephrotoxicity.
Tobramycin should be used with caution in newborns and premature babies, as their kidneys have not yet fully matured.
If any signs of renal toxicity or otovestibular toxicity occur, treatment with tobramycin should be stopped immediately.
When tobramycin is administered by inhalation, it may cause coughing, chest tightness or wheezing. If this happens, the treatment with the drug should be suspended and the doctor should be immediately informed who will decide what to do.
The use of tobramycin can promote the development of secondary infections (superinfections) from resistant bacteria or fungi.
Tobramycin may aggravate muscle weakness in patients with pre-existing severe myasthenia or pre-existing Parkinson's disease.
Tobramycin could cause side effects that could affect the ability to drive or use machines, therefore, caution should be used.
Interactions
Concomitant use of tobramycin and other nephrotoxic and / or ototoxic drugs should be avoided. Among these drugs, we recall:
- Bacitracin, vancomycin, viomycin, polymyxin B or colistin, other antibiotic drugs;
- Kanamycin, gentamicin, amikacin, neomycin, streptomycin or paromomycin, other aminoglycosides;
- Cisplatin and other platinum compounds used in cancer therapy;
- Amphotericin B, an antifungal;
- Ciclosporin or tacrolimus, immunosuppressive drugs used in the prevention of transplant rejections;
- Cephaloridine, cephalothin and other cephalosporins;
- Powerful diuretics, such as etacrinic acid, furosemide or mannitol .
In any case, it is still necessary to inform your doctor if you are taking - or if you have recently been - medicines of any kind, including over-the-counter drugs and herbal and / or homeopathic products.
Side effects
Tobramycin can cause various types of side effects, although not all patients experience them. This is due to the different sensitivity that each individual has towards the drug. Therefore, it is not said that the adverse effects occur all with the same intensity in each person.
The following are the main adverse effects that can occur during tobramycin therapy.
Kidney and urinary tract disorders
Treatment with tobramycin may cause:
- Alterations in renal function that occur with increased total and urea blood urea nitrogen and creatininemia;
- oliguria;
- cylindruria;
- Increased proteinuria.
Ear and labyrinth disorders
Tobramycin therapy can cause:
- Dizziness;
- Tinnitus, an auditory disorder characterized by the perception of whistling, buzzing, hissing, tinkling, etc .;
- Hearing loss;
- Hearing loss.
Neuromuscular block and respiratory paralysis
Treatment with tobramycin can cause neuromuscular blockage accompanied by respiratory paralysis which requires immediate treatment.
In addition, secondary or prolonged apnea may occur in anesthetized patients and in therapy with the drug.
Skin and subcutaneous tissue disorders
Treatment with tobramycin may cause:
- Skin eruptions;
- Itch;
- Urticaria;
- Skin discoloration;
- Dry skin;
- Skin inflammation.
Gastrointestinal disorders
Tobramycin therapy can cause nausea, vomiting and diarrhea.
Nervous system disorders
Treatment with tobramycin can cause headaches, drowsiness, mental confusion and disorientation.
Changes in blood composition
The use of tobramycin can lead to:
- Increased blood levels of liver transaminases;
- Increased blood lactate dehydrogenase concentration;
- Hypocalcemia, hypomagnesaemia, hyponatremia and hypokalemia, respectively, decrease in the amount of calcium, magnesium, sodium and potassium in the bloodstream;
- Leukopenia, ie the decrease in the number of white blood cells in the bloodstream;
- Leukocytosis, ie an increase in the number of white blood cells in the blood;
- Eosinophilia, ie an increase in the number of eosinophils in the bloodstream;
- Anemia;
- Plateletopenia, ie decrease in the number of platelets in the blood.
Side effects typical of ocular administration
In addition to some of the adverse effects described above, tobramycin administered via the eye can cause:
- Ocular discomfort;
- Eye redness;
- Inflammation of the eye surface;
- Vision impairment;
- Blurred vision;
- Corneal Abrasion;
- Swelling of the eye and eyelid;
- Eye dryness;
- Ocular secretion or itching;
- Increased tearing.
Side effects typical of inhaled administration
In addition to some previously described side effects, treatment with inhaled tobramycin may cause:
- Cough;
- Hoarseness;
- hypersalivation;
- Inflammation of the tongue;
- Noisy breath;
- Dryness of the mucosa;
- Blood in the sputum;
- Throat and chest pain;
- Shortness of breath;
- Sputum production higher than normal;
- Chest constriction;
- Breathing difficulty.
Overdose
In case of overdose with tobramycin administered parenterally, renal, auditory and / or vestibular toxicity, neuromuscular blockage, respiratory paralysis or respiratory failure may occur. These symptoms require immediate treatment.
Neuromuscular blockade can be treated with calcium salts and the necessary supportive therapies must be started.
Hemodialysis can be useful for eliminating excessive amounts of tobramycin from the bloodstream.
If you use more eye drops or more ophthalmic ointment than the prescribed one, instead, you need to rinse the eye with warm water and inform your doctor immediately.
In the case of inhaled preparations, if an excessive dose of tobramycin is given, the voice could become very hoarse and, in any case, it is necessary to contact the doctor immediately.
Action mechanism
Tobramycin is an aminoglycoside and, as such, exerts its antimicrobial action by interfering with bacterial protein synthesis.
Protein synthesis within bacterial cells occurs thanks to ribosomes. These organelles consist of ribosomal RNA and proteins associated with each other to form two subunits: the 30S subunit and the 50S subunit.
The ribosome has the task of translating the messenger RNA coming from the cell nucleus and of synthesizing the proteins for which it encodes.
Tobramycin binds to the 30S ribosomal subunit and, in doing so, can prevent messenger RNA from binding to the ribosome and can also induce a "misreading" of the messenger RNA itself, forcing the ribosome to synthesize "wrong" proteins called non-proteins. -sense.
Some of these nonsense proteins are included in the bacterial cell membrane altering their permeability. The alteration of the permeability of the membrane allows the entry of another antibiotic into the cell, thus causing a total block of protein synthesis.
Mode of Use - Posology
As mentioned in the introduction of this article, tobramycin is available for:
- Administration by inhalation in the form of a solution to be sprayed or capsules containing powder for inhalation;
- Administration by eye in the form of eye drops or ophthalmic ointment;
- Intramuscular or intravenous administration as an injectable solution.
Below are some indications on tobramycin doses that are usually used in therapy.
In any case - if deemed necessary - the doctor may vary the dose of tobramycin administered and the duration of the treatment.
Administration by inhalation
When using the tobramycin-based solution to be sprayed, it is recommended to take the drug twice a day (with an interval of twelve hours between one administration and another) for at least 28 days of therapy followed by another 28 days of pause. without taking the drug. The cycle should be repeated until the doctor decides to stop the therapy.
When using the capsules containing the powder for inhalation with the appropriate inhaler, however, the recommended dose of tobramycin is four capsules twice a day, with an interval of twelve hours between one administration and another.
Administration by eye
When using tobramycin based eye drops, it is recommended to instill two drops of the drug in the conjunctival sac four times a day in acute forms and three times a day in chronic forms, or according to medical prescription.
If prolonged-release eye drops are used, it is advisable to instill a drop of the drug in the conjunctival sac in the morning and one drop in the evening, or according to a medical prescription.
The ophthalmic ointment must be applied in the conjunctival sac 2-4 times a day, according to medical prescription.
Intramuscular or intravenous administration
The dose of tobramycin usually given in adults is 3-6 mg / kg of body weight, to be taken in a single dose.
In children, the dose of tobramycin usually used is 6-7.5 mg / kg of body weight per day, to be administered in 3-4 divided doses and at regular intervals.
In newborns and premature babies, the dose of tobramycin usually administered is 4 mg / kg of body weight per day, to be taken in two divided doses at a distance of twelve hours from each other.
In patients with renal insufficiency, minor doses of tobramycin will be given compared to those usually used.
Pregnancy and breastfeeding
The use of tobramycin administered parenterally by pregnant women is contraindicated, as the drug is able to cross the placenta and may cause fetal harm. The use of parenteral tobramycin is also contraindicated in mothers who are breast-feeding due to the possible damage it could cause to the newborn.
With regard to preparations based on tobramycin to be administered by inhalation or by ophthalmic means, pregnant women and breastfeeding mothers - before taking these drugs - must absolutely seek advice from the doctor who will decide what to do.
Contraindications
The use of tobramycin is contraindicated in the following cases:
- In patients with known hypersensitivity to tobramycin itself;
- In patients with known hypersensitivity to other aminoglycosides;
- In pregnancy and during lactation (only when tobramycin is administered parenterally).
