1) A patient with Parkinson's disease was hospitalized for aspiration pneumonia and could no longer take oral medications. It is important to switch such patients from oral to intravenous antiparkinsonian drugs to prevent complications. 2) When switching from L-DOPA to intravenous levodopa, the guidelines recommend administering 50-100 mg of levodopa for every 100 mg of oral L-DOPA, or a total levodopa equivalent dose. 3) For this patient taking 300 mg of L-DOPA daily, the recommendation would be to administer 150-300 mg of intravenous levodopa per day to match the oral dose. Continuous intravenous infusion is an alternative to divided administration.

1. Daisuke Yamamoto
Department of Neurology, Shonan Kamakura General Hospital
How to switch
oral antiparkinsonian drugs
to intravenous drugs
in Parkinson disease .

2. Introduction
Research anticipates that 1 in 1000 people and 1 in 100
elderly develop Parkinson disease (PD). Thus, there are
several cases of acute hospitalizations in patients with PD. In
such a situation, a sudden cessation of antiparkinsonian drugs
could induce neuroleptic malignant syndrome. Therefore,
during disease treatment, it is imperative to manage the
discontinuation of oral antiparkinsonian drugs and switch to
intravenous drugs, which might eventually affect hospitalization.
Through this presentation, I would like suggest a way to
resolve this problem. I hope this presentation is helpful,
especially for medical doctors who cannot consult a specialist.

3. The occurrence of PD is attributed to the deficiency of dopamine
in the brain. At present, several types of drugs are available for PD
treatment. Among several drugs, L-DOPA supplements dopamine
itself.
Some brand names of L-DOPA are Sinemet, Madpar, or Prolopa.
First, physicians must check whether a patient is taking these drugs
and ascertain their dosages.
The minimum knowledge
of antiparkinsonian drugs <1>.
→ The main antiparkinsonian drug is L-DOPA.

4. In principle, half the dose of orally administered L-DOPA
should be used for intravenously administering levodopa.
In addition, levodopa should be diluted with normal saline.
The minimum knowledge
of antiparkinsonian drugs <2>
→If a patient cannot take drugs orally,
physicians should switch to
intravenous administration of levodopa.

5. Dopamine agonists (DAs) constitute one group of antiparkinsonian
drugs; DA is the second most crucial drug after L-DOPA. In case of
difficulty in swallowing, DA administration should be discontinued;
however, a discontinuation might exacerbate the psychotic state,
resulting in dopamine agonist withdrawal syndrome (DAWS).
Thus, an early continuation of DA is desirable to avoid DAWS.
The minimum knowledge of
antiparkinsonian drugs <3>.
→the cessation of dopamine agonist
might pose a risk of developing DAWS.

6. [If a patient with PD has to discontinue oral intake of L-DOPA in
situations like surgery, 50– 100 mg levodopa is to be
intravenously per 100 mg L-DOPA once in the morning of the
operation day. This can be continued the next day; the dose of
levodopa can be increased according to the symptoms.]
The guidelines on PD treatment by Japanese Society of Neurology
recommend two ways of switching drugs.
<1> Guidelines for the treatment of PD (2011)

7. [Switch 100-mg L-DOPA to 50–100 mg levodopa, and administer it in
2–3 h . It can also be administered in 1 h.]
The guidelines on PD treatment by Japanese Society of Neurology
recommend two ways of switching drugs.
<2> The guidelines for the treatment of PD (2002)
In the clinical practice, we often chose the latter.
However, there are no clear guidelines to switch drugs.

8. There exists a more precise approach of
switching from L-DOPA to levodopa.
Precisely, all antiparkinsonian drugs should be changed to their
levodopa equivalent. The website below helps easily detail
Levodopa Equivalent Dose of all drugs.
http://www.parkinsonsmeasurement.org/toolBox/levodopaEquivalentDose.htm

9. Ideally, the Levodopa Equivalent Dose of all drugs should be
converted in terms of intravenous levodopa; however, it is not
always recommended to change all antiparkinsonian drugs
because of the differences in administration route.
There might arise a possibility of high levodopa level in the
blood. To avoid this problem, I suggest changing only L-DOPA
to levodopa. Thus, in this manner, please note that a lower
Levodopa Equivalent Dose would be attained.

10. A patient with PD who was prescribed 300-
mg/day L-DOPA was admitted to the hospital
because of aspiration pneumonia. As a result
of which, he could not take the medicine orally.
In this case ,
300-mg L-DOPA should be changed to
levodopa,
↓
50–100 mg levodopa should be administered
per 100 mg L-DOPA, or
↓
150–300 mg/day levodopa should be
administered.
Prescription
example
Prescription:
levodopa 50 mg
+ normal saline 100 mL
Administer three times a day,
dripping in 2 h
(total levodopa: 150 mg/day)

11. The purpose of switching therapy
The first objective of switching therapy is to prevent the
development of neuroleptic malignant syndrome.
Another objective is to maintain patients’ activities of daily
living (ADL) and to prevent swallowing dysfunction.
A continuous administration of antiparkinsonian drugs is
needed to avoid these problems.

12. Continuous intravenous infusion would maintain a constant
blood level of levodopa. Consequently, this therapy would
result in better ADL compared with the therapy involving
divided administration. This therapy can be performed safely,
and I suggest its efficacy in certain cases. Please consider
only one option of the treatment.
Another way
→The continuous
intravenous infusion of levodopa therapy

13. A patient with PD who was prescribed 300-
mg/day L-DOPA was admitted to the
hospital because of aspiration pneumonia.
He was unable to take medicine orally.
↓
In such a case, switch to continuous
intravenous infusion of levodopa.
Example
Japanese levodopa brand:
Dopaston 1A (20 mg, 20 mL)
Dopaston 6A + normal saline 180 mL
This prescription contains 300 mg
levodopa and 300 mL liquid volume.
Prescription
example Prescription:
Dopaston 6A + normal saline
180 mL
If this is administered at 10 mL/h,
the total amount of levodopa would
be 240 mg/day, which is almost
similar to that in divided
administration. If the patient’s ADL
is inadequate, a dose of 20 or 30
ml/h can also be administered.

14. Following patient consent,
an NG tube can also be considered to administer drugs.
Of note, sustained-release preparations
cannot be administered from the NG tube.
However, a rotigotine patch can be administered
without interruption.

15. Irrespective of the clinical department you are working in,
you would face this problem. There is no clear guideline
for switching antiparkinsonian drugs. If you cannot
consult a specialist in your hospital, PD treatment can be
managed by the method proposed in this presentation .
TAKE HOME MESSAGE!

16. If you have any further questions, or any opinions,
please contact us.
d_yamamoto@shonankamakura.or.jp