Zofran and Nausea

[Guest guest]

Laurie,

You wrote, " I am taking 12mgs [Zofran] every four hours. Can you take too

much Zofran? Is there a rebound effect? "

Nausea is certainly a distressing condition. I don't think there is anything

that can put me down quicker. There are a few things that have helped ease

this for me. The first thing was to make sure I was getting the medication

into my system. To improve my ability to breakdown and absorb medications, any

that were available were converted to elixirs, sublingual, topical, etc.

Zofran, fortunately, was one of them.

Zofran, ondansetron, is available is numerous forms. There are 4 mg & 8 mg

tablets as well as ODT, or Orally Disintegrating Tablets. The ODT is also

called a Melt or Oral lyophilisate. It is a freeze dried, fast dispersing oral

dosage form. It isn't a sublingual medications, as it is placed on top of the

tongue, where it will disperse within seconds, then swallowed. There is also

a once daily 24 mg tablet, a sugar-free strawberry flavored oral solution

containing 4 mg per 5 ml, suppository, and both IM and IV injections.

Following oral administration, Zofran is passively and well absorbed from

the GI tract and undergoes first pass metabolism. Peak plasma concentrations

are attained approximately 1.5 hours after an 8 mg dose and half-life 5 hours.

The effects of the medications will be felt before it peaks, but should not

be evaluated until that time. The time it takes to peak seems rather long when

you are nauseated, but knowing this may give a perspective on if its

working or not. Some people may think it should be working its best quicker than

that, when it may be doing what it is supposed to do. The half life explains why

the dose is no more frequent than every four hours. Sometimes, if a

medication is ordered 10 mg every four hours, you can take 5 mg every two

hours, and

it works, but you cannot repeat a dose prior to its half life. The

recommended dose for oral administration is 8 mg twice daily, no more than 24

mg daily.

It is, also, recommend to take the Zofran before the event that might cause

nausea. When I am having periods of continuous nausea, I take a dose of

Zofran on an empty stomach before my meal or snack. That way the sensors that

trigger the nausea are medicated and under control.

It is interesting to note that the pharmacokinetic properties of Zofran are

unchanged on repeat dosing. This means that a tolerance is not built up after

repeated usage, whereas with narcotics, we tend to need more and more and

more. So, if 8 mg doesn't work well, it is likely that it is the medication,

not the dose. Of course, it may also be changing the route of administration,

would make a difference, particularly in persons with gastric disorders. There

is no indication of rebound episode.

You mentioned taking 12 mg instead of the 8 mg. It is important to know that

for doses above 8 mg, effects are not proportional to dose. This means an 8

mg dose doesn't work twice as well, fast, etc., as a 4 mg dose. Zofran

research showed that the pharmacokinetics from a 16 mg tablets was 24% greater

than

predicted from an 8 mg dose, where it should have been twice as predicted.

the significance of this is that if you are not experiencing effective results

following 8, possibly 12 mg, then increasing the dose will not result in

increased efficacy. It will, however, result in increased potential of adverse

reactions.

Manifestations of overdoses that have been reported include visual

disturbances, severe constipation, hypotension and a vasovagal episode with

transient

second degree AV block. In all instances, the events resolved completely.

There is no specific antidote for Zofran, so every precaution should be made to

avoid any possible overdose.

Keeping you in thought & prayer,

Karyn E. , RN,

Exec. Director PAI / 1-

KarynWms@...

http://www.pancassociation.org