HMD
HMD - General Information
An inhibitor of DOPA decarboxylase, preventing conversion of levodopa to dopamine. It is used in parkinson disease to reduce peripheral adverse effects of levodopa. It has no antiparkinson actions by itself. [PubChem]
Pharmacology of HMD
HMD, a noncompetitive decarboxylase inhibitor, is used in combination with levodopa for the treatment of Parkinson's disease.
HMD for patients
Carbidopa is used with levodopa to treat Parkinson's disease. Parkinson's disease
is believed to be related to low levels of a chemical called dopamine (DOE pa meen)
in the brain. Levodopa (Dopar, Larodopa) is turned into dopamine in the body.
Carbidopa is used with levodopa to prevent the breakdown (metabolism) of levodopa
before it can reach the brain and take effect. Carbidopa is only effective if it is
taken with levodopa. It has no effect if it is used alone. Carbidopa is used with
levodopa to treat the stiffness, tremors, spasms, and poor muscle control of
Parkinson's disease. These medications are also used to treat the same muscular
conditions when they are caused by drugs such as chlorpromazine (Thorazine),
fluphenazine (Prolixin), perphenazine (Trilafon), and others.
HMD Interactions
Caution should be exercised when the following drugs are administered concomitantly with LODOSYN (Carbidopa) given with levodopa or carbidopa-levodopa combination products.
Symptomatic postural hypotension has occurred when LODOSYN, given with levodopa or carbidopa-levodopa combination products, was added to the treatment of a patient receiving antihypertensive drugs. Therefore, when therapy with LODOSYN, given with or without levodopa or carbidopa-levodopa combination products, is started, dosage adjustment of the antihypertensive drug may be required.
For patients receiving monoamine oxidase inhibitors, see CONTRAINDICATIONS. Concomitant therapy with selegiline and carbidopa-levodopa may be associated with severe orthostatic hypotension not attributable to carbidopa-levodopa alone.
There have been rare reports of adverse reactions, including hypertension and dyskinesia, resulting from the concomitant use of tricyclic antidepressants and carbidopa-levodopa preparations.
Dopamine D2 receptor antagonists (e.g., phenothiazines, butyrophenones, risperidone) and isoniazid may reduce the therapeutic effects of levodopa. In addition, the beneficial effects of levodopa in Parkinson's disease have been reported to be reversed by phenytoin and papaverine. Patients taking these drugs with LODOSYN and levodopa or carbidopa-levodopa combination products should be carefully observed for loss of therapeutic response.
Iron salts may reduce the bioavailability of carbidopa and levodopa. The clinical relevance is unclear.
Although metoclopramide may increase the bioavailability of levodopa by increasing gastric emptying, metoclopramide may also adversely affect disease control by its dopamine receptor antagonistic properties.
HMD Contraindications
LODOSYN is contraindicated in patients with known hypersensitivity to any component of this drug.
Nonselective monoamine oxidase (MAO) inhibitors are contraindicated for use with levodopa or carbidopa-levodopa combination products with or without LODOSYN. These inhibitors must be discontinued at least two weeks prior to initiating therapy with levodopa. SINEMET (Carbidopa-Levodopa), or levodopa may be administered concomitantly with the manufacturer's recommended dose of an MAO inhibitor with selectivity for MAO type B (e.g., selegiline HCl).
Levodopa or carbidopa-levodopa products, with or without LODOSYN, are contraindicated in patients with narrow-angle glaucoma.
Because levodopa or carbidopa-levodopa products, with or without LODOSYN, may activate a malignant melanoma, they should not be used in patients with suspicious, undiagnosed skin lesions or a history of melanoma.
Additional information about HMD
HMD Indication: For treatment of the symptoms of idiopathic Parkinson's disease (paralysis agitans), post-encephalitic parkinsonism
Mechanism Of Action: When mixed with levodopa, carbidopa inhibits the peripheral conversion of levodopa to dopamine and the decarboxylation of oxitriptan to serotonin by aromatic L-amino acid decarboxylase. This results in increased amount of levodopa and oxitriptan available for transport to the CNS. HMD also inhibits the metabolism of levodopa in the GI tract, thus, increasing the bioavailability of levodopa.
Drug Interactions: Not Available
Food Interactions: Not Available
Generic Name: Carbidopa
Synonyms: Alpha-Methyldopahydrazine; Carbidopa Anhydrous; Carbidopa Monohydrate; Carbidopum [Inn-Latin]; N-Aminomethyldopa
Drug Category: Dopamine Agents; Antiparkinson Agents; Antidyskinetics
Drug Type: Small Molecule; Approved
Other Brand Names containing Carbidopa: Atamet; HMD; Lodosin; Lodosyn;
Absorption: Rapidly decarboxylated to dopamine in extracerebral tissues so that only a small portion of a given dose is transported unchanged to the central nervous system.
Toxicity (Overdose): Symptoms of a carbidopa toxicity include muscle spasms or weakness, spasms of the eyelid, nausea, vomiting, diarrhea, an irregular heartbeat, confusion, agitation, hallucinations, and unconsciousness.
Protein Binding: 76%
Biotransformation: Rapidly decarboxylated to dopamine
Half Life: 1-2 hours
Dosage Forms of HMD: Tablet Oral
Chemical IUPAC Name: (2S)-3-(3,4-dihydroxyphenyl)-2-hydrazinyl-2-methylpropanoic acid
Chemical Formula: C10H14N2O4
Carbidopa on Wikipedia: https://en.wikipedia.org/wiki/Carbidopa
Organisms Affected: Humans and other mammals
