Ototoxic Drugs

Let's start with this case scenario.....

CC: A 55 years old patient, known case of HF and IHD, presented to ED complaining of hearing loss for 2 days.

HPI: hearing loss is bilateral, started gradually, progressive with no aggravating or relieving factors and associated with vertigo. Patient denied pain, fever, or trauma to his head or ear.

Past Hx: Patient has Hx of IHD, HF, and he was just diagnosed with malaria since he came back from Jazan 2 months ago. He was also diagnosed with testicular tumor. Patient denied any major or minor surgical procedures.

Medications: Aspirin, furosemide, quinine, cisplatin.

Allergy: NKA

Family Hx: His father was diagnosed with reversible drug induced hearing loss after the use of vancomycin and gentamicin.

Social Hx: Patient is working in his farm,

and he is a smoker for 25 years.

Clases of Ototoxic Drugs:

1- Antibiotics:

Aminoglycosides are bactericidal inhibitors of protein synthesis.

2- Loop Diuretics:

inhibit the cotransport of sodium potassium, and chloride.

3- Anti-neoplastic agents:

Chemotherapeutic agents : Alkylating agents are used IV and distribute to most tissues and cleared unchanged from kidney

Clases of Ototoxic Drugs:

4- Salicylates:

inactivation of the cyclooxygenase (COX) enzyme. Cyclooxygenase is required for prostaglandin and thromboxane synthesis.

5- Anti-malarial drugs:

Quinine complexes with double stranded DNA to prevent DNA replication and RNA transcription ,  it is Blood schizonticides 

Examples of Ototoxic Drugs:

Mechanism of Ototxicity:

*Aminoglycoside:

Mechanism of Ototxicity:

*Aspirin:

Salicylic acid quickly enters to cochlea

perilymph levels produce tinnitus & hearing loss.

The mechanism is multifactorial

but cause metabolic changes

rather than morphologic changes within the cochlea.

Mechanism of Ototxicity:

*Diuretics:

• Furosemide and Ethacrynic acid.
• Know to cause edema and cystic changes in stria vascularis of cochlear duct.
• The edema is caused due to blockage of Na+ &Cl- ions transport

• Effect: mostly reversible but permanent damage may occur.

Risk Factors That Potentiate Ototoxicity of The Drugs:

There are certain factors may put the patients at increased risk for ototoxicity:

• Large doses and long duration of therapy
• Elderly patient
• Patient with hearing problems
• Renal insufficiency
• Family history of ototoxicity

*Precautions which should be observed in high risk and pregnant patients when they receive ototoxic drugs*

Precautions of Ototoxic Drugs:

1- Pregnant women and children should not be given ototoxic medications if a non-toxic alternative is available    

2- An evaluation of a pre-existing condition of hearing impairment should be done before prescribing ototoxic antibiotics.

3- Hearing ability has to be monitored through audiometric exams throughout the therapy

Precautions of Ototoxic Drugs:

4- According to the American Speech-Language-Hearing Association (ASHA) a tonal audiometric exam should be carried out 24 hours after the beginning of the therapy and every two or three days for the rest of the therapy.

5-Pregnant women may be at risk of exposing their unborn child to substances harmful to the child’s hearing.

So avoid using of Fluoroquinolones categories C  & Aminoglycosides (Amikacin, Gentamicin, and Tobramycin) categories D.  Not recommended in pregnancy

•• should use the minimum dose with maximum effectiveness to avoid harmful effects.

Thank You...

Lma Humaied Alkhaldi

Rahaf Sfran Alharthui

Khairiah Yaqoup Alqashqari

Enas Fadel Kamal

Waad Daif Allah Alotaibi

Azah Aziz Alharthi

Hanan Husain AL-Malki

Eatezaz Yahia Alzahrani

Rahaf Hashim Fatta

Raghad Khaled Althbety

Ghaida Turkii Alrobaiee

Maha Safar Althwaiby

Rawan Marzoq AlTwiriqi

Ohoud Daif Allah Alotaibi