Doprin - General Information
The naturally occurring form of dihydroxyphenylalanine and the immediate precursor of dopamine. Unlike dopamine itself, it can be taken orally and crosses the blood-brain barrier. It is rapidly taken up by dopaminergic neurons and converted to dopamine. It is used for the treatment of parkinsonian disorders and is usually given with agents that inhibit its conversion to dopamine outside of the central nervous system. [PubChem]
Pharmacology of Doprin
Doprin (L-dopa) is used to replace dopamine lost in Parkinson's disease because dopamine itself cannot cross the blood-brain barrier where its precursor can. However, L-DOPA is converted to dopamine in the periphery as well as in the CNS, so it is administered with a peripheral DDC (dopamine decarboxylase) inhibitor such as carbidopa, without which 90% is metabolised in the gut wall, and with a COMT inhibitor if possible; this prevents about a 5% loss. The form given therapeutically is therefore a prodrug which avoids decarboxylation in the stomach and periphery, can cross the blood-brain barrier, and once in the brain is converted to the neurotransmitter dopamine by the enzyme aromatic-L-amino-acid decarboxylase.
Doprin for patients
Stopping this medication suddenly can cause Parkinson's disease to worsen quickly. Report bothersome or unexpected side effects. Unless prescribed, do not take levodopa in addition to this drug. Avoid pyridoxine (vitamin B6) if you are taking levodopa alone, although it can be taken with carbidopa/levodopa. Avoid high-protein meals for maximum absorption. If you are taking the sustained-release tablet, swallow a whole or one-half tablet without chewing or crushing it. Onset of effect of the first morning dose of the sustained release product could be delayed up to 1 hour compared with the quick-release product. A dark color (red, brown, or black) might appear in saliva, urine, or sweat and can stain clothing.
Monoamine oxidase (MAO) inhibitors and Larodopa should not be given concomitantly and these inhibitors must be discontinued 2 weeks prior to initiating therapy with Larodopa. Larodopa is contraindicated in patients with known hypersensitivity to the drug and in narrow angle glaucoma.
Because levodopa may activate a malignant melanoma, it should not be used in patients with suspicious, undiagnosed skin lesions or a history of melanoma.
Additional information about Doprin
Doprin Indication: For the treatment of idiopathic Parkinson's disease (Paralysis Agitans), postencephalitic parkinsonism, symptomatic parkinsonism which may follow injury to the nervous system by carbon monoxide intoxication, and manganese intoxication.
Mechanism Of Action: Striatal dopamine levels in symptomatic Parkinson's disease are decreased by 60 to 80%, striatal dopaminergic neurotransmission may be enhanced by exogenous supplementation of dopamine through administration of dopamine's precursor, levodopa. A small percentage of each levodopa dose crosses the blood-brain barrier and is decarboxylated to dopamine. This newly formed dopamine then is available to stimulate dopaminergic receptors, thus compensating for the depleted supply of endogenous dopamine.
Drug Interactions: Not Available
Food Interactions: Not Available
Generic Name: Levodopa
Synonyms: L-Dihydroxyphenylalanine; L-DOPA; DOPA; 3,4-dihydroxyphenylalanine
Drug Category: Dopamine Agents; Antiparkinson Agents; Antidyskinetics
Drug Type: Small Molecule; Approved
Absorption: Levodopa is rapidly absorbed from the proximal small intestine by the large neutral amino acid (LNAA) transport carrier system.
Toxicity (Overdose): Oral, mouse: LD50 = 2363 mg/kg; Oral, rabbit: LD50 = 609 mg/kg; Oral, rat: LD50 = 1780 mg/kg.
Protein Binding: High
Biotransformation: 95% of an administered oral dose of levodopa is pre-systemically decarboxylated to dopamine by the L-aromatic amino acid decarboxylase (AAAD) enzyme in the stomach, lumen of the intestine, kidney, and liver. Levodopa also may be methoxylated by the hepatic catechol-O-methyltransferase (COMT) enzyme system to 3-O-methyldopa (3-OMD), which cannot be converted to central dopamine.
Half Life: 50 to 90 minutes
Dosage Forms of Doprin: Tablet Oral
Chemical IUPAC Name: (2S)-2-amino-3-(3,4-dihydroxyphenyl)propanoic acid
Chemical Formula: C9H11NO4
Levodopa on Wikipedia: https://en.wikipedia.org/wiki/Levodopa
Organisms Affected: Humans and other mammals