Supplementary information regarding Transtympanic Gentamicin
Timothy C. Hain,
Last edited: 8/01. Please read our disclaimer.
Local anesthesia for TTG (or myringotamy)
- A drop of phenol on the ear drum is the most commonly used method of numbing
the ear drum. It burns for a few minutes but leaves an area on the drum that
is numb for several weeks.
- Less long lasting anesthesia can be obtained with tetracaine or lidocaine,
with or without iontophoresis.
- EMLA creme (lidocaine with prilocaine) can also be used.
Delivery systems for gentamicin
- Needle injection through a myringotamy
- Butterfly catheter T-tube assembly
- Micro Wick placed through a tympanostomy tube
- Microcatheter pump through tympanostomy tube
At the present writing, it doesn't seem to matter what delivery system is used
to administer gentamicin. The cheapest approach appears to be the simple needle
injection method. The Silverstein "Micro-Wick" requires a tympanostomy
tube. The Microcatheter pump also requires a more invasive approach.
For weekly injections, concentrations of 20 to 40 mg/ml are made up, buffered
with bicarbonate, and injected so as to fill the middle ear. Between one and
6 injections are administered, typically once/week.
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