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CASE 2, Both at proximal tubule, 2 OAT Involved in tubular excretion,…
CASE 2
Probenecid
MOA of Probenecid
Increase rate of uric acid excretion accompanied by the presence of renal tubular blocking agent
Inhibit
OAT at basolateral membrane of cell
URAT receptor in apical membrane
MOA of Organic Anion Transporter (OAT)
Regulates ion balance in the body
OAT 3
OAT 1
Controls the excretion of common drugs, toxins and endogenous metabolites into the urine.
Mediates and regulates renal absorption and the excretion of the drugs
Oral Contraceptive
Uses
Control pregnancy
Prevent or delay the ovulation
Progesterone inhibit FSH production
Maintain estrogen level
No surge in estrogen, no ovulation occur
2 Types
Combination pill of Estrogen and Progestogen
Progestogen-only pill
Absorption of Ethinyl estradiol
Weak acid (pKa 10)
Undissociated drug readily absorb in acidic environment
Better absorption in small intestine (pH 6.5-7.4)
Slower absorption in stomach pH (4-6.5)
Enterohepatic recycling
Involves biliary secretion and intestinal reabsorption of a solute
Sometimes with hepatic conjugation and intestinal deconjugation.
In liver
Steroid hormone
are conjugated to allow the excretion of bile
Through
Glucuronidation
Sulfonation
Also found excreted in
Urine
Feces
In gut
Conjugated hormones that excreted in the bile can be deconjugated
by beta-glucuronidase bacteria
Allow to be reabsorbed into circulation
Ampicillin
Physiochemical properties of Penicillin
Penicillin is a beta-lactam antibiotics which has narrow spectrum antibiotic, meaning that it is effective against a relatively narrow range of bacteria.
It is hydrophilic, so it is easily excreted.
Melting point: 214-217'C
Interaction with Oral Contraceptive
Interrupt normal microbiota in gut
Less steroid hormones can be deconjugated and reabsorbed into circulation
Reduces the level of bacteria in gut
More steroid hormones will be excreted
Less bioavailability of the drugs
Interaction with Probenecid
Prolong the plasma level of penicillin and increase penicillin efficacy.
Examples of drugs that are being excreted with the help of OAT
Other beta-lactam antibiotics
Cephalosporin
Penicillin
Methotrexate
Probenecid blocked OAT and URAT and decrease the elimination or excretion of some drugs such as penicillin that is supposed to be excreted by these transporters.
Patient Benefits on Probenecid-Penicillin Interaction
Penicillin has a shorter half life
Patients will not getting any therapeutic effect of penicillin if they take the penicillin only
It will be excreted out faster from the body exert its therapeutic effects.
By consuming penicillin and probenecid , penicillin will be retained in the blood plasma to prolong the duration of penicillin.
Antibacterial mechanism of Penicillin is increase while Penicillin excretion through the urine decrease.
Both at proximal tubule
.
.
Reabsorption of uric acid from proximal tubule is prevented
2 OAT Involved in tubular excretion
.
.
An uricosoric agent - Decrease uric acid level in blood
in Tubular
Excretion
Julia
Bob
Ref :
https://www.healthywomen.org/condition/birth-control-pills
Ref :
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5017946/
Ref :
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5045553/
Ref :
https://www.medicinenet.com/probenecid-oral/article.htm
Ref :
https://www.ncbi.nlm.nih.gov/books/NBK548599/
Ref :
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5017946/
