Brief Answer:
About 90% elimination in 24 hours

Detailed Answer:
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Fioricet(acetaminophen) with codeine is used in analgesia to relieve pain.The peak effect of codeine is seen after 2-4 hours and 90% of the drug gets eliminated through the urine in 24 hours. Similarly about 80-90% of acetaminophen also gets eliminated through urine in 24 hours.
Codeine is an opioid and it works through the opioid receptors in brain to cause sedation and analgesia.Acetaminophen is a nonsteroid antiinflammatory medication and it does not causes sedation unlike codeine.

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Brief Answer:
Half life about 3 hours

Detailed Answer:
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The plasma half life of codeine is about 3 hours and 90% of oral dose is excreted in the urine within 24 hours of the dosing.With usual therapeutic dose the peak effect of analgesia(pain relief) reaches at about 2 hours and the effect persists for 4-6 hours.

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Brief Answer:
Details below

Detailed Answer:
Difference between oral and intravenous medication is that the time to achieve peak affect is less in intravenous medication.
In oral medication the drug has to pass through the gut and liver before reaching the blood circulation.In intravenous medication the drug reaches directly to the blood and thus the time of peak effect is earlier in comparison to oral medication.But once the drug reaches to the circulation the metabolism is same irrespective of the route of administration.
So it is not like that effect of oral medication lasts longer than intravenous.
The usual dose of codeine tablet is 1-2 tablet 2-4 hourly depending on the severity.It should be taken under physician supervision.
In case of excessive sedation the dose may need to be decreased.

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