How long will 2 units of Botox last?

Botox usually lasts 3 months, but feel it is doubtful that it could cause dry mouth. Check other supplements or medications to ensure they don't have a side effect profile that includes dry mouth.

Botox takes 1-2 weeks for final results and will resolve in 3-4 months, however the side effects will dissipate over time. Best, Dr. Emer

Thank you for your question. Botox is used to relax
facial tissues and soften them. It usually takes about 3-7 days to see the effect
and it will last up to 3 months. However, two units of Botox cannot cause dry
mouth as the dosage is too low. I recommend you consult an expert to determine the best treatment
plan for you. All the best!

2-3 units of Botox at the base of the nose is a nice trick to lift the nose tip. It would last 2-3 months. It would not be the cause of any dry mouth symptoms. I would explore other reasons.

A small dose such as 2 units should not last long. Even though Botox can last 3-4 months, smaller amounts typically last a lot less, and you may only see an effect for about 2 months.
I agree that the dry mouth is unlikely to be the result of Botox as well.