The mainstay of therapy for motor symptoms of Parkinson disease are: Levodopa, dopamine agonists, monoamine oxidase (MAO) B inhibitors, anticholinergic agents, amantadine, catechol-O-methyl transferase (COMT) inhibitors, estrogen and other drugs such as Exenatide, uric acid, isradipine, nilotinib and GDNF infusion.

Treatment choices for some of the nonmotor symptoms of PD are:

psychosis: quetiapine, clozapine and pimavanserin.

Dementia: Cholinesterase inhibitors such as rivastigmine and donepezil.

Fatigue: Amantadine, methylphenidate and pemoline.

Depression: Amitriptyline, desipramine, citalopram ,paroxetine, venlafaxine, ropinirole and pramipexole.

Constipation: Increasing probiotics and fibers, lubiprostone and polyethylene glycol.

Sialorrhea: chewing gum and hard candy but in severe cases, botulinum toxin injection into salivary glands .

Sexual dysfunction: sildenafil (for male)

Ortostatic hypotention: Fludrocortisone, Sympathomimetic agents such as ephedrine, pseudoephedrine, methylphenidate and dextroamphetamine.

The mainstay of therapy for motor symptoms of Parkinson disease are:

• Levodopa: This drug is the most effective in controlling motor symptoms in PD patients.^[1][2] If we use levodopa alone, it will convert to dopamine in the peripheral circulation, so we combine it with a decarboxylase inhibitor like carbidopa to prevent this. The ratio of carbidopa_levodopa in tablets are 10/100, 25/100 or 25/250.^[3][4] The adverse effects of this drug includes elevated serum homocysteine, low levels of vitamin B12, elevated methylmalonic acid and sensorimotor peripheral neuropathy.^[5][6][7][8] It can also cause motor fluctuations, dyskinesia, cramps and dystonia.^[9][10] One of the concerns regarding long term use of levodopa is that it may be increase the rate of dopamine neurons degeneration^[11] but other studies demonstrated  that it does not damage neurons.^[12][13]
• Dopamine agonists: Dopamine agonist such as bromocriptine, pramipexole and ropinirole are proved to be effective in managing motor symptoms of PD patients.^[14] At first, the use of dopamine agonist were limited t the condition where there is reduced levodopa response or when we had disturbing levodopa complications^[15][16] but since dopamine agonists have fewer side effects, some experts suggest using these drugs as the first line therapy especially for PD patients under 60 years old.^[17] The adverse effects of dopamine agonist are nausea, vomiting, sleep disorders, confusion, peripheral edema and valvular heart disease.^[18][19]
• Monoamine oxidase (MAO) B inhibitors: MAO B inhibitors such as selegiline, rasagiline and safinamide are proved to be helpful in managing motor symptoms of PD patients.^{[20][21][22][23]} these drugs can cause nausea and headaches.^[21] Rasagiline can also cause impulse control disorders.^[24]
• Anticholinergic agents: In PD we have reduced amount of dopamine and excess amount of cholinergic effects, so anticholinergic drugs such as trihexyphenidyl and benztropine can reduce the symptoms of PD.^[25][26][27]
• Amantadine: Amantadine, an antiviral drug can improve PD symptoms by increasing dopamine release, inhibition of dopamine reuptake, stimulation of dopamine receptors and anticholinergic effect.^[28][29] Some studies showed that in controlling bardykinesia, this drug can be more effective than anticholinergic drugs.^[30]
• Catechol-O-methyl transferase (COMT) inhibitors: The catechol-o-methyl transferase (COMT) inhibitors such as entacapone and tolcapone can potentiate the effect of levodopa in reducing PD motor symptoms.^[31][32]
• Estrogen: In postmenopausal women who are experiencing motor fluctuation on antiparkinsonism drugs we can use low dose estrogen to improve their condition.^[33][34]
• Other agents: Other drugs such as Exenatide^[35], uric acid^[36], isradipine^[37], nilotinib^[38] and GDNF infusion^[39] can be effective in controlling PD patients symptoms.

Treatment choices for some of the nonmotor symptoms of PD are:

• Psychosis: Drugs such as quetiapine, clozapine and pimavanserin are used in managing psychosis in PD.^[40][41] one of the side effects of clozapine is leukopenia and agranulocytosis.^[42]
• Dementia: Cholinesterase inhibitors such as rivastigmine and donepezil are the main treatment of dementia in PD.^[43][44][45]
• Fatigue: Amantadine, methylphenidate and pemoline can improve fatigue in PD patients.^[46][47][48]
• Depression: Amitriptyline^[49], desipramine, citalopram^[50],paroxetine, venlafaxine^[51], ropinirole and pramipexole^[52][53][54] are useful in managing depression in PD patients. If we intent to use tricyclics we should be aware that their anticholinergic effect can increase orthostatic hypotension and cognitive impairment^[55] and for SSRI we should know that they can cause dystonia, tremor and parkinsonism.^[56] the combination of MAO B inhibitors with SSRIs or tricyclics can cause serotonin syndromes^[57]
• Constipation: Increasing probiotics and fibers, lubiprostone and polyethylene glycol are effective in treatment of constipation.^[58][59][60]
• Sialorrhea: If the sialorrhea is mild we can treat it with chewing gum and hard candy^[61][62] but in severe cases, botulinum toxin injection into salivary glands is helpful.^[52][63]
• Sexual dysfunction: Male sexual dysfunction can be treated with sildenafil.^[64]
• Ortostatic hypotention: Fludrocortisone^[65], Sympathomimetic agents such as ephedrine, pseudoephedrine, methylphenidate and dextroamphetamine are used to treat orthostatic hypotension.^[66][67]