Here.Metabolism
Cetirizine does not undergo extensive metabolism.[3] It is notably not metabolized by the cytochrome P450 system.[36] Because of this, it does not interact significantly with drugs that inhibit or induce cytochrome P450 enzymes such as theophylline, erythromycin, clarithromycin, cimetidine, or alcohol.[3] While cetirizine does not undergo extensive metabolism or metabolism by the cytochrome P450 enzyme, it does undergo some metabolism by other means, the metabolic pathways of which include oxidation and conjugation.[3][2] Plasma radioactivity attributed to unchanged cetirizine is more than 90% at 2 hours, 80% at 10 hours, and 70% at 24 hours, indicating limited and slow metabolism.[2] The enzymes responsible for transformation of cetirizine have not been identified.[3]
Elimination
Cetirizine is eliminated approximately 70 to 85% in the urine and 10 to 13% in the feces.[3] About 50 or 60% of cetirizine eliminated in the urine is unchanged.[3][2] It is eliminated in the urine via an active transport mechanism.[2] The elimination half-life of cetirizine ranges from 6.5 to 10 hours in healthy adults, with a mean across studies of approximately 8.3 hours.[3][2] Its duration of action is at least 24 hours.[2] The elimination half-life of cetirizine is increased in the elderly (to 12 hours), in hepatic impairment (to 14 hours), and in renal impairment (to 20 hours).
Moclobemide The risk or severity of adverse effects can be increased when Moclobemide is combined with Levocetirizine.
Just to re-iterate - while I'm happy to help you in your pathway towards understanding, we really can't give out medical advice. The main thing to be aware of is, in my view, the question of whether Passiflora would decrease the urinary clearance of levocetirizine leading to a risk of overdose. Quite a lot of work has been done lately by the European medicines and health agency on herbal medications so it's likely there would be something there about known interactions from Passiflora, albeit not necessarily with levocetirizine.This information should not be interpreted without the help of a healthcare provider. If you believe you are experiencing an interaction, contact a healthcare provider immediately. The absence of an interaction does not necessarily mean no interactions exist.
The effects on the urinary system of the substances named in the flavonoids section is where I would suggest you start looking.Constituents:
Flavonoids, mainly C-glycosides of apigenin and luteolin, e.g. isovitexin, isoorientin and their 2"-β-D-
glucosides, schaftoside, isoschaftoside, vicenin-2 and swertisin, with considerable variation in
qualitative and quantitative composition according to source (Hänsel et al., 1994; Bradley, 1992;
Wichtl, 2004; Barnes et al., 1996; 2007; ESCOP, 2003; PDR for herbal medicines, 1998; Weniger &
Anton, 1996).
Maltol which, however, may be an artefact (Hänsel et al., 1994; Bradley, 1992; Barnes et al., 1996
and 2007; ESCOP, 2003; Weniger & Anton, 1996).
Essential oil in trace amounts comprising more than 150 components (Hänsel et al., 1994; Bradley,
1992; Wichtl, 2004; Barnes et al., 1996 and 2007; ESCOP, 2003; PDR for herbal medicines, 1998;
Weniger & Anton, 1996).
Gynocardin (a cyanogenic glycoside) (Hänsel et al., 1994; Bradley, 1992; Wichtl, 2004; ESCOP, 2003;
PDR for herbal medicines, 1998; Weniger & Anton, 1996).
β-carboline alkaloids (e.g. harman, harmol, harmalol) may be present in traces. However, these
alkaloids are undetectable in most commercial materials (ESCOP, 2003).
A tri-substituted benzoflavone derivative (Dhawan et al., 2004). The presence of this substance in
Passiflora incarnata has later been questioned by Holbik et al.,2010, who were unable to repeat
isolation of the substance from plant materials of three different geographical origins.