In the treatment of
Parkinson's disease,
levodopa, DCI,
MAO-B inhibitor, COMT inhibitors,
dopamine receptor agonists,
amantadine,
anticholinergics have been applied and new drugs are being developed.
Levodopa is still the golden standard in the treatment of
Parkinson's disease. The study on
levodopa bioavailability showed 3-4 times differences in individual patients. Drug-food interactions are prominent in
levodopa. Low
protein food increased
levodopa bioavailability and improved no ON or delayed ON in the treatment of
Parkinson's disease. Vitamine C or
magnesium did not alter the bioavailability of
levodopa. The bioavailability of
levodopa between the
levodopa/carbidioa (100/12.5) group and the
levodopa/
benserazide (100/25) group was studied in patients with
Parkinson's disease by population PK study. C(max) of
levodopa in levodeopa/
benserazide group was twice as high as in
levodopa/
carbidopa group.
Domperidone, a
dopamine receptor antagonist applied as an
antiemetic inceases vowel movement. The effect of
domperidone on
levodopa bioavailability was studied, and the combination of
domperidone with
levodopa increased AUC of
levodopa. Clarythromycin or grape fruit juice inhibits both of
CYP3A4 and
P-glycoprotein which work on metabolism and absorption of drugs. Coadministration of clarythromycin with
ergot alkaloids such as
cabergoline or
bromocriptine increased the AUC up to 2-3 times.
Amantadine is excreted through kidney without being metabolized and renal function is the most important factor in the blood concentration of
amantadine. In elder women with the
body weight of 50 kg or less,
creatinine clearance is less than 50 ml/min even though the serum
creatinine is within the normal range.
Selegiline is metabolized through
CYP2D6 and 3A4. Coadministration of qunidine,
cimetidine, maclorides, antifungals, grape fruit juice increase the bioavailability of
selegiline and may augment the antiparkinsonian effect.