Pharmacokinetics and tolerability of inhaled levodopa from a new dry-powder inhaler in patients with Parkinson's disease.

BACKGROUND: Inhaled levodopa may quickly resolve off periods in Parkinson's disease. Our aim was to determine the pharmacokinetics and tolerability of a new levodopa dry-powder inhaler. METHODS: A single-centre, single-ascending, single-dose-response study was performed. Over three visits, eight Parkinson's disease patients (not in the 'off state') received by inhalation 30 mg or 60 mg levodopa, or their regular oral levodopa. Maximum levodopa plasma concentration (C max), time to maximum plasma concentration (Tmax) and area under the concentration time curve 0-180 min were determined. Spirometry was performed three times at each visit. RESULTS: After inhalation, levodopa T max occurred within 15 min in all participants, whereas after oral administration, T max ranged from 20 min to 90 min. The bioavailability of inhaled levodopa without carboxylase inhibitor was 53% relative to oral levodopa with carboxylase inhibitor. No change in lung-function parameters was observed and none of the patients experienced cough or dyspnoea. No correlation was observed between inhalation parameters and levodopa pharmacokinetic parameters. CONCLUSION: Inhaled levodopa is well tolerated, absorbed faster than oral levodopa, and can be robustly administered over a range of inhalation flow profiles. It therefore appears suitable for the treatment of off periods in Parkinson's disease.

Ready-to-use parenteral amiodarone: a feasibility study towards a long-term stable product formulation.

OBJECTIVES: To determine the feasibility of preparing a long-term stable ready-to-use parenteral amiodarone formulation using cyclodextrins as dissolution enhancer. METHODS: A preformulation study was performed with different molar ratios of hydroxypropyl-beta-cyclodextrin (HP-BCD) or sulfobutylether-beta-cyclodextrin (SBE-BCD) to amiodarone in order to investigate enhancement of amiodarone's water solubility. Further, effects of pH and temperature on the dissolution rate during production were investigated. Shelf-life was determined for a ready-to-use iso-osmotic preparation of 1.8 mg/mL amiodarone with SBE-BCD in a molar ratio of 1:3. Amiodarone content was assessed using a validated high-pressure liquid chromatography ultraviolet method. RESULTS: Amiodarone-SBE-BCD in a molar ratio of 1:3 at pH 4.0-5.0 yielded the best results in terms of increased solubility and dissolution time (90 min). With SBE-BCD, a smaller molar ratio to amiodarone was needed than with HP-BCD. The amiodarone content of the final formulation stored 12 months at 21°C in daylight remained unchanged. CONCLUSIONS: A ready-to-use or ready-to-administer amiodarone product, prepared in a hospital pharmacy, for intravenous application in an acute clinical setting is a feasible option from a chemical, physical and microbiological point of view. The availability of such a product will have a significant impact on medication safety, and production should therefore be considered.

Effect of Rectal Levodopa Administration: A Case Report.

OBJECTIVE: The aim of this report is to discuss whether or not rectal levodopa administration is useful in some situations. BACKGROUND: In situations where oral intake of levodopa formulations is not possible, the treatment options of Parkinson's disease patients are limited. The literature describes no or low rectal absorption of levodopa. CASE DESCRIPTION: A patient with an ileus was unable to take oral medication. After consulting the neurologist and pharmacist, the surgeon decided to describe a rectal formulation of levodopa/carbidopa (100/25 mg) once daily. On day 3 of the therapy, 1 h after administration of the rectal formulation of levodopa/carbidopa, a blood sample was drawn. The patient was unable to take his other Parkinson medication; therefore the dose of the rectal levodopa/carbidopa was increased to 5 times a day. RESULTS: Full control of the symptoms was not achieved, but alleviation of the most severe tremor and rigidity was seen, which was confirmed by the neurologist, nurses and patient. The levodopa concentration detected was 17 nmol/l. Compared to levodopa concentrations described in the literature (1,400-12,000 nmol/l), the concentration is very low. There are some possible explanations for the low concentration detected. The presence of a specific amino acid transport system in the rectum is not known, which could lead to no or reduced absorption. The poor rectal absorption of carbidopa leads to a higher conversion of levodopa to dopamine peripherally. CONCLUSIONS: In situations where patients are unable to take oral medication, rectal administration of levodopa/carbidopa is worth considering.

A levodopa dry powder inhaler for the treatment of Parkinson's disease patients in off periods.

Adequate treatment of Parkinson's patients in off periods with orally administered levodopa is hindered by a poor bioavailability and a slow onset of action. Hence, there is a need for a fast and reliable alternative as for instance via pulmonary administration of the drug. We developed a levodopa containing powder formulation for pulmonary delivery by a recently presented high dose dry powder inhaler (Cyclops). The objective was to produce the drug formulation by means of simple techniques such as micronization, either as pure active substance or with a minimum amount of excipients. After an initial screening on dispersion behaviour, the most promising formulation in the Cyclops was characterized in vitro over a range of pressure drops (2-6 kPa) and doses (20, 30 and 40 mg), representative of those to be expected in practice. A co-micronized levodopa formulation with 2% L-leucine appeared to yield the best aerosol properties for inhalation and highest delivered dose reproducibility. The combination of this particular formulation and the Cyclops inhaler seems to meet the basic requirements for satisfactory deposition in the airways. This formulation is therefore expected to be a promising candidate for the treatment of Parkinson's patients in an off period.