BMA Concise Guide to Medicine & Drugs


Brand names Cidomycin, Genticin, Minims gentamicin

Used in the following combined preparation Gentisone HC


Drug group Aminoglycoside antibiotic

Overdose danger rating Low

Dependence rating Low

Prescription needed Yes

Available as generic Yes


Gentamicin is one of the aminoglycoside antibiotics. The injectable form is usually reserved for hospital treatment of serious infections. These include lung, urinary tract, bone, joint, and wound infections, as well as peritonitis, septicaemia, and meningitis. This form is also used together with a penicillin for prevention and treatment of heart valve infections (endocarditis).

In the form of drops, gentamicin is used to treat eye and ear infections. Gentamicin given by injection can have serious adverse effects on the ears and the kidneys. Damage to the ears may lead to deafness and problems with the balance mechanism in the inner ear. Courses of treatment are, therefore, limited to seven days when this is possible. Treatment is monitored by measuring blood levels of gentamicin, especially when high doses are needed or kidney function is poor.


Your drug prescription is tailored for you. Do not alter dosage without checking with your doctor.

How taken/used Injection, eye/ear drops.

Frequency and timing of doses 1–3 x daily (injection); 3–4 x daily or as directed (ear drops); every 2 hours or as directed (eye drops).

Adult dosage range According to condition and response (injection); according to your doctor’s instructions (eye and ear drops).

Onset of effect Within 1–2 hours.

Duration of action 8–12 hours.

Diet advice None.

Storage Keep in original container at room temperature out of the reach of children.

Missed dose Apply eye/ear preparations as soon as you remember.

Stopping the drug Complete the course. Even if you feel better, the original infection may still be present and may recur if treatment is stopped too soon.

Exceeding the dose Although overdose by injection is dangerous, it is unlikely because treatment is carefully monitored. For other preparations of the drug, an occasional unintentional extra dose is unlikely to cause concern. But if you notice any unusual symptoms, notify your doctor.


Adverse effects are rare but those that occur with the injected form of the drug may be serious. Dizziness, vertigo, impaired hearing, and changes in the urine (such as bloody or cloudy urine) should be reported to your doctor promptly and you should stop using the drug. Nausea and vomiting may also occur. If ear drops are used when the eardrum is perforated, damage to the inner ear may occur. Blurred vision or eye irritation may occur with the eye preparations and should be reported to your doctor. Allergic reactions, including rash and itching, may occur with all preparations that contain gentamicin. If such reactions do occur, stop using the drug and contact your doctor immediately.


General note A wide range of drugs, including furosemide, vancomycin, and cephalosporins, increase the risk of hearing loss and/or kidney failure with gentamicin given by injection.


Be sure to tell your doctor if:

· You have a long-term kidney problem.

· You have a hearing disorder, especially a perforated eardrum.

· You have myasthenia gravis.

· You have Parkinson’s disease.

· You have previously had an allergic reaction to aminoglycosides.

· You are taking other medicines.

Pregnancy No evidence of risk with eye or ear drops. Injections are not prescribed, as they may cause hearing defects in the baby. Discuss with your doctor.

Breast-feeding No evidence of risk with eye or ear preparations. Given by injection, the drug may pass into the breast milk. Discuss with your doctor.

Infants and children Reduced dose necessary for injections.

Over 60 Increased likelihood of adverse effects. Close monitoring of treatment is therefore necessary.

Driving and hazardous work No known problems from preparations for the eye or ear.

Alcohol No known problems.


Not usually given for longer than seven days. When given by injection, there is a risk of adverse effects on hearing and balance.

Monitoring Blood levels of the drug are usually checked if it is given by injection. Tests on kidney function are also usually carried out.


Brand name None

Used in the following combined preparations None


Drug group Drug for diabetes

Overdose danger rating High

Dependence rating Low

Prescription needed Yes

Available as generic Yes


Glibenclamide is an oral antidiabetic drug belonging to the sulphonylurea class. Like other drugs of this type, it stimulates the production and secretion of insulin from the islet cells in the pancreas. This promotes the uptake of sugar into body cells, thereby lowering the blood sugar level.

Glibenclamide is used in the treatment of Type 2 diabetes, in conjunction with exercise and a diet that is low in sugar and fats.

In conditions of severe illness, injury, or stress, glibenclamide may lose its effectiveness, making insulin injections necessary. Adverse effects are generally mild. The commonest side effect is hypoglycaemia (low blood sugar). Symptoms of poor diabetic control will occur if the dosage of glibenclamide is not appropriate.


Your drug prescription is tailored for you. Do not alter dosage without checking with your doctor.

How taken/used Tablets.

Frequency and timing of doses Once daily in the morning with breakfast.

Adult dosage range 5–15mg daily.

Onset of effect Within 3 hours.

Duration of action 10–15 hours.

Diet advice An individualized diabetic diet must be maintained in order for the drug to be fully effective. Follow the advice of your doctor.

Storage Keep in original container at room temperature out of the reach of children. Protect from light.

Missed dose Take with next meal; do not double the dose to account for missed dose.

Stopping the drug Do not stop the drug without consulting your doctor; stopping the drug may lead to worsening of your diabetes.


Seek immediate medical advice in all cases. If any early warning symptoms of excessively low blood sugar (such as fainting, sweating, trembling, confusion, or headache) occur, eat or drink something sugary. Take emergency action if seizures or loss of consciousness occur.


Serious adverse effects are rare with glibenclamide. Symptoms such as dizziness, fainting, confusion, weakness, tremor, and sweating may be signs of low blood sugar due to lack of food or too high a dose of the drug. If any such symptoms occur, eat or drink something sugary immediately and seek medical assistance. Other possible adverse effects include constipation, diarrhoea, nausea, vomiting, rash, itching, and weight changes. Discuss with your doctor if they occur. If jaundice develops, consult your doctor without delay.


General note A variety of drugs may reduce the effect of glibenclamide and so may raise blood sugar levels. These include corticosteroids, oestrogens, diuretics, and rifampicin. Others increase the risk of low blood sugar. These include warfarin, aspirin, sulphonamides and other antibacterials, antifungals, NSAIDs, and ACE inhibitors.

Beta blockers may mask symptoms of hypoglycaemia, especially non-cardioselective beta blockers such as propranolol.


Be sure to tell your doctor if:

· You have long-term liver or kidney problems.

· You are allergic to sulphonylurea drugs.

· You have thyroid problems.

· You have porphyria.

· You have ever had problems with your adrenal glands.

· You are taking other medicines.

Pregnancy Not usually prescribed. Insulin is generally substituted in pregnancy because it gives better diabetic control.

Breast-feeding The drug passes into the breast milk and may cause low blood sugar in the baby.

Infants and children Not prescribed.

Over 60 Reduced dose may be necessary. Greater likelihood of low blood sugar exists when glibenclamide is used.

Driving and hazardous work Usually no problems. Avoid these activities if you have warning signs of low blood sugar.

Alcohol Avoid. Alcoholic drinks may upset diabetic control increasing the risk of hypoglycaemia.

Surgery and general anaesthetics Notify your doctor or dentist that you have diabetes before undergoing any surgery.

Sunlight and sunbeds Avoid exposure to sunlight and tanning beds. The drug may make your skin more sensitive.


No problems expected.

Monitoring Regular testing of blood sugar control is required. Periodic assessment of the eyes, heart, and kidneys may also be advised.