Tricyclic antidepressants levodopa

Orthostatic hypotension Antihypertensives Diuretics Levodopa Tricyclic antidepressants... 

Opioids, benzodiazepines, barbiturates, corticosteroids, dopamine agonists (e.g., amantadine, bromocriptine, levodopa, pergolide, pramipexole, ropinirole), H2-receptor antagonists, anticholinergics (e.g., diphenhydramine, trihexylphenidyl), P-adrenergic blockers, clonidine, methyldopa, carbamazepine, phenytoin, baclofen, cyclobenzaprine, lithium, antidepressants (e.g., tricyclic antidepressants, selective serotonin reuptake inhibitors), and interleukin-2... 

Antihypertensives, diuretics, antipsychotics, tricyclic antidepressants, levodopa, dopamine agonists, a-blockers Corticosteroids NSAIDs, anticoagulants -Blockers (non-selective)... 

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. 

Levodopa or dopamine agonists produce diverse dyskinesias as a dose-related phenomenon in patients with Parkinson s disease dose reduction reverses them. Chorea may also develop in patients receiving phenytoin, carbamazepine, amphetamines, lithium, and oral contraceptives, and it resolves with discontinuance of the offending medication. Dystonia has resulted from administration of dopaminergic agents, lithium, serotonin reuptake inhibitors, carbamazepine, and metoclopramide and postural tremor from theophylline, caffeine, lithium, valproic acid, thyroid hormone, tricyclic antidepressants, and isoproterenol. 

Rasagiline Inhibits MAO-B selectively, higher doses also inhibit MAO-A Increases dopamine stores in neurons may have neuroprotective effects Parkinson s disease adjunctive to levodopa smooths levodopa response Oral Toxicity interactions may cause serotonin syndrome with meperidine, and theoretically also with selective serotonin reuptake inhibitors, tricyclic antidepressants... 

The anticholinergic effects of imipramine and other tricyclic antidepressants can delay gastrointestinal motility enough to interfere with the absorption of various other drugs. Such was the case in an experimental study of the absorption of levodopa in four healthy subjects (177). It is likely that this effect may interfere with absorption of other drugs, especially those, such as chlorpromazine, that are extensively metabolized in the gut. 

Interactions. With nonselective monoamine oxidase inhibitors (MAOI), the monoamine dopamine formed from levodopa is protected from destruction it accumulates and also follows the normal path of conversion to noradrenaline (norepinephrine), by dopamine (J-hydroxylase severe hypertension results. The interaction with the selective MAO-B inhibitor, selegiline, is possibly therapeutic (see below). Tricyclic antidepressants are safe. Levodopa antagonises the effects of antipsychotics (dopamine receptor blockers). Some antihypertensives enhance hypotensive effects of levodopa. Metabolites of dopamine in the urine interfere with some tests for phaeochromocytoma, and in such patients it is best to measure the plasma catecholamines directly. 

Clinically important, potentially hazardous interactions with amitriptyline, amoxapine, amphetamines, bupropion, citalopram, clomipramine, cyproheptadine, desipramine, dextroamphetamine, dextromethorphan, diethylpropion, dopamine, doxepin, entacapone, ephedra, ephedrine, epinephrine, fluoxetine, fluvoxamine, ginseng, imipramine, levodopa, mazindol, meperidine, methamphetamine, nefazodone, nortriptyline, paroxetine, phendimetrazine, phentermine, phenylephrine, pizotifen, propoxyphene, protriptyline, pseudoephedrine, rizatriptan, sertraline, sibutramine, sumatriptan, sympathomimetics, tramadol, tricyclic antidepressants, trimipramine, tryptophan, venlafaxine, zolmitriptan... 

Antidepressants selective serotonin reuptake inhibitors, tricyclic antidepressants Antihypertensives felodipine Antibiotics quinolones, isoniazid Bronchodilators albuterol, theophylline Corticosteroids prednisone Dopa agonists levodopa Herbals ma huang, ginseng, ephedra Nonsteroidal anti-inflammatory drugs ibuprofen Stimulants amphetamines, methylphenidate, caffeine, cocaine Sympathomimetics pseudoephedrine Thyroid hormones levothyroxine Toxicity anticholinergics, antihistamines, digoxin Withdrawal alcohol, sedatives... 

Symptoms t BP, arrhythmias, excitation, hyperthermia ° Drugs releasers (i.e., tyramine), tricyclic antidepressants (TCAs), agonists, levodopa... 

Remember that levodopa is a precursor of norepinephrine and epinephrine as well as dopamine and that norepinephrine and epinephrine are metabolized primarily by monoamine oxidase type A. In the presence of nonselective inhibitors of monoamine oxidases, levodopa may cause a hypertensive crisis. Though not contraindicated in Parkinson s disease, tricyclic antidepressants may interfere with the effectiveness of levodopa. The answer is (D). 

Information seems to be limited to these reports. Concurrent use is normally successful and uneventful. However, be alert for the possibility of a hypertensive reaction, which resolves if the tricyclic antidepressant is withdrawn. See also Levodopa+Antimuscarinics , p.682 for interactions due to the antimuscarinic adverse effects of tricyclic antidepressants. 

Edwards M. Adverse interaction of levodopa with tricyclic antidepressants. Practitioner (1982)226, 1447 and 1449. 

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... 

Erectile dysfunction (ED), the inability to achieve or maintain a penile erection sufficient to permit satisfactory sexual intercourse, is estimated to affect over 100 million men worldwide, with a prevalence of 39% in those of 40 years. Its numerous causes include cardiovascular disease, diabetes mellitus and other endocrine disorders, alcohol and substance abuse, and psychological factors (14%). While the evidence is not conclusive, drug therapy is thought to underlie 25% of cases, notably from antidepressants (SSRI and tricyclic), phenothiazines, cypro-terone acetate, fibrates, levodopa, histamine H -receptor blockers, phenytoin, carbamazepine, allopurinol, indomethacin, and possibly adrenoceptor blockers and thiazide diuretics. 

The concurrent use of levodopa and the tricyclics is usuaiiy une-ventfui aithough two unexplained hypertensive crises have occurred when imipramine or amitriptyline was used with ievodopa/carbidopa. See also Levodopa + Antimuscarinics , p.682 for interactions due to the antimuscarinic effects of tricyciic antidepressants. 

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