L-DOPA is a natural amino acid found in food. It is used to increase dopamine levels in people with Parkinson’s disease. Apart from being a medicinal preparation, it is also found in a large number of herbal supplements available without a prescription. The effect? Increase in muscle mass in athletes using L-DOPA.
How is L-DOPA important for athletes?
Some studies show that taking L-DOPA increases libido and serves in bodybuilding as a means of increasing the synthesis of human growth hormone . An increase in muscle mass has been observed in athletes using L-DOPA. Motor control is also improved. L-DOPA also shows remarkable effects on glucose metabolism as well as vasopressor properties.
Biosynthesis
L-DOPA (3,4-dihydroxy-L-phenylalanine) is a natural amino acid present in food. It is synthesized in the human body from another amino acid: L-tyrosine with the help of the enzyme tyrosine hydroxylase. L-DOPA is converted to dopamine in the brain during decarboxylation. The prefix “L-” indicates its levorotation property (compared to the dextrorotation of D-DOPA). It is also a precursor molecule for the catecholamine neurotransmitter norepinephrine (norepinephrine) as well as the hormone epinephrine ( adrenaline ).
In clinical practice, the drug is known as Levodopa (INN) (Synonyms: Dopaflex, Caldopa).
Therapeutic use
L-DOPA is used to increase dopamine levels in Parkinson’s disease and some types of dystonia. It crosses the blood-brain (chemo-encephalic) barrier, while dopamine cannot. Once in the central nervous system, Levodopa is metabolized to dopamine by the enzyme aromatic L-amino acid decarboxylase. Pyridoxal phosphate (vitamin B6) is required as a cofactor for decarboxylation and is therefore often co-administered with levodopa (usually as pyridoxine).
Effects
The conversion of L-DOPA to dopamine takes place in peripheral tissues, ie outside the brain. This is also the mechanism of the observed side effects. In standard clinical practice, a peripheral DOPA decarboxylase inhibitor, Carbidopa or Benserazide, is often prescribed, often a catechol-O-methyltransferase (COMT) inhibitor, to prevent the synthesis of dopamine in peripheral tissues. An interesting fact is that green tea is a natural decarboxylase inhibitor.
L-DOPA can be metabolised directly by catechol-O-methyltransferase (COMT) to 3-O-methyldopa (3-OMD). This metabolic pathway does not exist in the healthy human body, but is important after peripheral L-DOPA administration in Parkinson’s patients or, in rare cases, in patients with enzyme deficiency of aromatic L-amino acid decarboxylase (AADC).
Side Effects
- Hypotension, especially when the dose is exceeded
- Arrhythmia
- Nausea: less pronounced with food
- Gastrointestinal bleeding
- Difficulty breathing
- Hair loss
- Confusion and disorientation
- Extreme emotional states – anxiety, restlessness, frequent and increased libido
- Sleep disorders
- Visual and auditory hallucinations
- Drowsiness
- Conditions similar to amphetamine psychosis
Contraindications
Atherosclerosis, hypertension , glaucoma, melanoma, bronchial asthma , cardiovascular failure, endocrine diseases. Restrictions: during / pregnancy, childhood (up to 12 years), history of myocardial infarction.
Toxicity
Some studies suggest a cytotoxic role of L-DOPA. Although the drug is generally harmless to humans, some studies in rats have shown an increase in cytotoxic markers in rat cell lines “pheochromocytoma PC12” after treatment with the drug. Other researchers have observed toxic effects in cell lines from nerve cells, quinone generation, and subsequent self-oxidation and cell death.
Supplements containing L-DOPA
Many herbal supplements contain standardized doses of L-DOPA and are available without a prescription. They are gaining popularity in the United States, their online sales are growing. The largest plant source of L-DOPA is the tropical legume Mucuna pruriens, also known as “Velvet Bean”.
