Improvement of dry mouth by replacing paroxetine with fluvoxamine.
OBJECTIVE
To present a case of improvement of paroxetine-induced dry mouth by substitution of fluvoxamine and analyze this case based on receptor occupancy theory.


METHODS
A 66-year-old woman with major depressive disorder had been treated with brotizolam 0.5 mg/day, flunitrazepam 2 mg/day, sulpiride 100 mg/day, bromazepam 2 mg/day, trazodone 25 mg/day, and paroxetine hydrochloride 10 mg/day. Although her psychological symptoms improved gradually, she complained of dry mouth. Paroxetine was replaced with fluvoxamine maleate 50 mg/day, and the dryness disappeared within a month.


CONCLUSIONS
We calculated the time courses of muscarinic acetylcholine (mACh) receptor occupancy after oral administration of paroxetine and fluvoxamine at the treatment doses by using pharmacokinetic parameters obtained from the literature. The mACh receptor occupancy was estimated to be decreased from 0.22% to 0.020% by replacing paroxetine with fluvoxamine.


CONCLUSIONS
The improvement of dry mouth observed after the replacement of paroxetine with fluvoxamine in this patient may have been due to a decrease in the mACh receptor occupancy.
Arima
Yuka
Y
Graduate School of Pharmaceutical Sciences, Kyushu University, 3-1-1 Maidashi, Higashi-ku, Fukuoka 812-8582, Japan.
Kubo
Chiharu
C
Tsujimoto
Masayuki
M
Ohtani
Hisakazu
H
Sawada
Yasufumi
Y
D000368:Aged; D003865:Major Depressive Disorder / Q000188:drug therapy*; D005260:Female; D016666:Fluvoxamine / Q000493:pharmacokinetics / Q000627:therapeutic use*; D006801:Humans; D017374:Paroxetine / Q000009:adverse effects* / Q000493:pharmacokinetics; D011976:Receptors, Muscarinic / Q000378:metabolism; D017367:Selective Serotonin Reuptake Inhibitors / Q000009:adverse effects* / Q000493:pharmacokinetics; D014987:Xerostomia / Q000139:chemically induced*
D016666:Fluvoxamine; D017374:Paroxetine; D011976:Receptors, Muscarinic; D017367:Selective Serotonin Reuptake Inhibitors