Answer:
The toxins of Clostridium botulinum are classified into eight immunologically
distinguishable exotoxins. The type A toxin is most easily produced
in culture. Its principal effect of muscle paralysis is caused by
the inhibition of the release of acetylcholine at the neuromuscular junction.
The paralytic effect is dose-related with peak effect occurring 5-7 days
after injection and lasting 4-6 months. Glabellar wrinkles are caused
by the action of the corrugator supercilli which serves to draw the eyebrows
medially and inferiorly. Toxin is injected in the muscle belly at two sites
on the medial edge of the supraorbital rim. Five units of toxin are recommended
per site. Complications include blepharoptosis, diplopia, globe perforations,
retrobulbar hemorrhage, lagophthalmos, epiphora, and ectropion. Unwanted
temporary effects include ecchymoses, eyebrow ptosis and asymmetry. Some
of these effects are related to migration of toxin which usually dissipates
in a few weeks.