Step I Ques..Glaucoma

[SYD]

Could somebody/ anybody clarify this please ??

Glaucoma MX-

Does Mydriatic( pupil dilatation) drugs make it better( curative).

I thought it was vice versa, 'cos when pupil dilates/pupillary constrictor muscle contracts there is crowding at the base making drainage of aquous fluid difficult/less..

Thanks

 

[SYD]

Its me again,

The q book answer is this-
Acute glaucoma Mx - Anti mucarinic/ Beta blockers

Don't they produce opposing effects ??

I am really confused 😕

 

[ckent]

What you probably read is anti-cholinergic *esterases* and beta blockers for glaucoma. It's not the miosis that the drugs cause that benefits glaucoma patient, it's the increase in outflow of aqueous humor or the decrease in production of aqueous humor.

 

[Ludy]

I think ckent is right about the anticholinesterases. The other drugs that can be used are muscarinic agonists like pilocarpine. They work for narrow-angle because they constrict the pupil and for open-angle because they increase the "tone" of the trabecular network, thereby increasing outflow of aqueous humor. As for beta-blockers, they're used because they decrease production of aqueous humor. There actually are no beta receptors on the ciliary muscles; the sympathetic receptors in the eye are alpha-1 receptors. So alpha agonists can be used to dilate the eye during eye exams.

 

[SYD]

Thanks guys

So, we use Beta (-) to reduce Aqueous production.
( S/E pupil dilatation - not good 'cos could worsen glaucoma ??)

Pilocarpine : Cholinomimetic (muscarine +) constrict pupil, increasing outflow.

In summary When pupil constricts its good for Glaucoma- makes sense, 'cos when we dilate the eye somebody said to me ask for glaucoma , Yeap.
🙂

 

[SYD]

I think I was wrong there

Rx can be

Anti ACh (-)- Physostigmine
ACh (+) Pilocarpine

Both costrict pupil- which should be good for a glaucoma eye.

Beta (-) reduce aqueous, does not dilate eye , cos ciliary muscle has no Beta, so no need to worry about S/E.

Then its only when we dilate with anti muscarinics we need to worry about making glaucome eye worse ... 😀

 

[BellKicker]

Don't forget alpha2-agonists (apraclonidine) and carbonic anhydrase inhibitors (acetazolamide).

And for those with waaay too much disk cortical diskspace: etacrynic acid.

Just took my pharm final yesterday. RRrrr.

Later.

 

[SYD]

Bell kicker

Acetazolamide, yes totally forgot about, now I recall..

Clonidine / Alfa 2 (+) : woouldn't it dilate the eye & make things worse ???

While your Pharm knowledge is saturating your brain I will thow in a question on PK/PD very soon, try and answer if you could..