Levodopa: Uses, Side Effects And Dosage etc

It is used for the treatment of Parkinsonian disorders (associated with low levels of a chemical known as dopamine)and is typically given with agents that inhibit its conversion to dopamine outside of the central nervous system.Levodopa is employed alone or together with carbidopa. Some patients need the combination of medication, whereas others benefit from L-dopa alone. By improving muscle control, L-dopa permits more normal movements of the body.

Clinical Uses:

• In The treatment of Parkinson’s disease L-dopa together with carbidopa is at first given in a small dose, like 25/100 mg (25 carbidopa and 100 levodopa) 3 times daily after meals to stop gastric irritation.The dose may be raised upto 25/250 mg 3-4 times daily.However its better to stay the dose of L-dopa low so as to avoid the adverse effects.
• L-dopa is particularly effective in Tremors and hypokinesia.

Pharmacokinetics:

When Given Orally,I is absorbed from the small intestine by an active process.Plasma half Life is about 2 hours and its onset of action happens in 1-2 hours.When It is given alone , it’s principally metabolised in the peripheral tissue into dopamine by the enzyme dopa decarboxylate enzyme, and only 1-3% of levodopa stay unchanged and passes into brain.

Mechanism Of Action:

In a Parkinson sickness the amount of dopamine become terribly low This is as a result of many of the cells in your brain that manufacture dopamine have died or are dying.Dopamine molecule is just too polar to cross the blood-brain barrier, and therefore cannot enter the brain.(Dopamine is lipid soluble and therefore cannot pass through blood brain barrier.) the most common treatment used contains the chemical levodopa. This molecule is additionally polar, but because it’s an amino acid it’s recognised by proteins that carry amino acids across the blood-brain barrier.Levodopa is thus safely transported across the interface. levodopa is the precursor Molecule of dopamine and A small proportion of each levodopa dose crosses the barrier and is decarboxylated to dopamine. This recently formed dopamine then is available to stimulate dopaminergic receptors, therefore compensating for the depleted supply of endogenous dopamine.Levodopa may be a chemical building block that your body converts into dopamine.

Levodopa Contraindications:

It is contraindicated in Narrow angle glaucoma,in gouty arthritis unless patient is protected with prophylactic anti gout therapy.It is conjointly contraindicated in malignant melanoma because levodopa increase the synthesis of melanin.

Levodopa side Effects:

• More Common and less serious side effects include constipation, dry mouth, or blurred vision;muscle twitches; sleep disorder, confusion, or nightmares; darkening of the pee or sweat, mild nausea, vomiting, or decreased appetite; hand tremor, fatigue, dizziness or sleepiness, agitation or anxiety.
• Serious side effects, an allergic reaction, seizures, an irregular heartbeat or fluttering within the chest, depression or suicidal thoughts, uncontrolled movements of a section of the body, persistent nausea, vomiting, or diarrhea, and unusual changes in mood or behavior.
• Very Rare side effects include glaucoma, Blood Dyscrasias, Gout, and brown discoloration of various body secretions

Levodopa in Pregnancy:

Levodopa should be used with caution in pregnant ladies.Animal studies show toxicity associated with the use of L-dopa. it may pass into breast milk and have an effect on milk production. Consult your doctor before breast-feeding.

Drug Interactions:

• Drug Like Pyridoxine (vitamin B6) will increase the peripheral metabolism of L-dopa which will be prevented by dopa decarboxylase inhibitors.
• Combination of adrenergic medicine with levodopa might cause hypertension (Blood Pressure).
• Administration of non selective Mono amine oxidase inhibitors (MAO) with Levodopa will cause hypertensive crisis.Thus it should be avoided with in two weeks of administration of Non selective MAO inhibitors or MAO-A inhibitors.

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