Levodopa drug interactions

Cohon, M.S. "Drug Interactions Involving Levodopa". Rev. Drug Interactions (1974), 1, 45-62. 

Some drug interactions observed with levodopa. 

Many other infrequent symptoms and abnormal laboratory findings have been associated with levodopa treatment. Metabolites cause the urine to turn reddish and then black. Many drug interactions are possible few are confirmed, but this possibility should be watched. Some monoamine oxidase inhibitors reported effective in Parkinson s disease caused hypertensive reactions in combination with levodopa, but tricyclic antidepressants... 

Levodopa interacts with many different drugs. When levodopa is used with phenytoin, reserpine, and papaverine, there is a decrease in response to levodopa The risk of a hypertensive crisis increases when levodopa is used with the monoamine oxidase inhibitors (see Chap. 31). Foods high in pyridoxine (vitamin B6) or vitamin B6 preparations reverse the effect of levodopa However, when carbidopa is used with levodopa, pyridoxine has no effect on the action of levodopa hi fact, when levodopa and carbidopa are given together, pyridoxine may be prescribed to decrease the adverse effects associated with levodopa... 

Drug/Food interactions Administration of a single dose of the extended-release form with food increased the extent of levodopa availability by 50% and increased peak levodopa concentrations by 25%. 

Pyridoxine [Vitamin B ] [Vitamin B Supplement] U e Rx prevention of vit B6 deficiency Action Vit supl Dose Adults. Deficiency 10-20 mg/d PO Drug-induced neuritis 100-200 mg/d 25-100 mg/d prophylaxis Peds. 5-25 mg/d x 3 wk Caution [A (C if doses exceed RDA), +] Contra Component aUCTgy Disp Tabs 25, 50, 100 mg inj 100 mg/mL SE Allergic Rxns, HA, N Interactions -1- Effects OF levodopa, phenobarbital, phenytoin EMS Can be used as an antidote for isoniazid poisoning OD May cause sensory nerve damage (numbness, tingling, reduced sensation) and coordination problems Sxs are usually revised aft stopping pyridoxine symptomatic and supportive... 

A growing number of drugs are used that affect the many neurotransmitters in the brain benzodiazepines and others act on GABAergic transmission antidepressants, such as monoamine oxidase inhibitors and tricyclic antidepressants, are thought to increase the concentration of transmitter amines in the brain and so elevate mood—these will also act at peripheral nerve terminals, so interactions with them are a combination of peripheral and central actions. Levodopa (L-dopa) increases central as well as peripheral dopamine, and the newer class of psychoactive drugs, the selective serotonin reuptake inhibitors (SSRIs) of which the ubiquitous fluoxetine (Prozac) is best known, act in a similar way on serotonergic pathways. 

Neither selegiline nor rasagiline should be taken by patients receiving meperidine. They should be used with care in patients receiving tricyclic antidepressants or serotonin reuptake inhibitors because of the theoretical risk of acute toxic interactions of the serotonin syndrome type (see Chapter 16), but this is rarely encountered in practice. The adverse effects of levodopa may be increased by these drugs. 

Metaproterenol (Alupent, Metaprel) [Bronchodilator/ Beta-Adrenergic Agonist] Uses Asthma reversible bronchospasm Action Sympathomimetic bronchodilator Dose Adults. Neb 0.2-0.3 mL in 2.5-3.0 mL of NS Peds. Neb 0.1-0.2 mL/kg of a 5% soln in 2.5 mL NS Caution [C, /-] Contra Tach, other arrhythmias Disp Aerosol 0.65 mg/inhal soln for inhal 0.4, 0.6% tabs 10, 20 mg syrup 10 mg/5 mL SE Nervousness, tremors (common), tach, HTN Interactions T Effects W/ sympathomimetic drugs, xanthines T risk of arrhythmias W/ cardiac glycosides, halothane, levodopa, theophylline, thyroid hormones T HTN W/ MAOIs effects W/ BBs EMS Separate additional aerosol use by 5 min fewer 3i effects than isoproterenol longer-acting monitor lung sounds before/after administration... 

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