Hearing loss and disturbances

High-pitched ringing in the ears (tinnitus), Hearing loss in higher frequencies, Deafness, Nausea, Vomiting and Dizziness (vertigo).

No structural changes to the quinolone ring have been identified as being associated with this adverse reaction. As such this is to be considered a class effect.

Although nausea, vomiting and dizziness (vertigo) is supposedly the number one adverse reaction to the fluoroquinolones we find no research regarding the association between toxicity in the vestibular organ and these events. Little to no information can be found regarding the tinnitus reaction. A search using ‘fluoroquinolone’ and ‘tinnitus’ on PubMed revealed but one article written in 1995 associating this reaction with Ciprofloxacin (but no abstract or text, just a title and author listing). However, one finds hundreds of articles encouraging the use of the fluoroquinolones to treat ‘otitis media’ a very common minor ear infection found in the pediatric population.

Some fluoroquinolones may cause toxicity in the vestibular organ where our sense of balance, position, motion and orientation in space is controlled. Nausea, vomiting and dizziness are signs of this kind of damage, with the dizziness presenting as a form of vertigo. The fluoroquinolones may also cause cochlear toxicity characterized by hearing loss or tinnitus (ringing in the ears).

The hair cells of the cochlea (neuroepithelium) represent the primary target in most fluoroquinolone-induced ototoxic adverse effects on hearing. To what extent an exogenically-induced morphologic damage to hair cells is reversible is not known. In aging structurally altered hair cells such damage may persist for years. As the hair cells continue to degenerate (thereby no longer participating in sensory transduction) secondary changes occur in the spiral ganglion cells and the neuronal pathways.

The link between function and morphology in the cochlea is very obvious regarding the high and middle frequencies with a distinct tonotopic localisation. Whereas for low frequencies (below 1 khz) such a specific morphologic correlation is lacking. Ototoxic effects primarily affecting the source for the production of endolymph, i.e. the stria vascularis, become manifest at all frequencies and at a rather early stage. Independent of type of substance penetrating into the inner ear, the substance has a considerably slower elimination rate as compared with all other compartments in the body. The toxicity of the drugs seems to be more related to its tissue binding capacity and saturation of receptor sites than related to the concentration of the drug in endo-or perilymph.

The first symptom of ototoxicity from the fluoroquinolones is typically a high-pitched ringing in the ears or hearing loss in higher frequencies. If the medication is stopped immediately, the tinnitus may go away within a couple of weeks. However, in some cases, a permanent and total loss of hearing can occur within a month or two.

The fluoroquinolones as a class are associated with deafness and reduced hearing. Health Canada has received 4 serious case reports of deafness or decreased hearing associated with ciprofloxacin. They involved men aged 35, 47, 65 and 67 years old. Three were receiving 1000 mg/d orally and one was receiving 800 mg intravenously. In all cases, the reactions began within 1 week after initiation of therapy. Three patients recovered, and the fourth experienced partial permanent deafness.