Tyramine Pressor Test Research Articles

Tyramine Pressor Sensitivity During Treatment With the Selegiline Transdermal System 6 mg/24 h in Healthy Subjects

The oral tyramine pressor test was administered to healthy males during treatment with a selegiline transdermal system (STS; 6 mg/24 h). The tyramine sensitivity factor (TSF) was calculated from the ratio of baseline and on-treatment tyramine pressor doses. The tyramine sensitivity factor value following 9 days of treatment with the selegiline transdermal system was 1.85 +/- 0.10. Extended treatment, 33 days, produced a small, clinically non-meaningful increase in this value. The tyramine sensitivity factor for the selegiline transdermal system was similar to that following treatment with 10 mg/d of oral selegiline capsules but more than 20 times less than observed during tranylcypromine treatment. A larger increase in the tyramine sensitivity factor was observed following extended selegiline transdermal system treatment at a higher dose (12 mg/24 h), which was significantly decreased following coadministration of tyramine capsules with a meal. These results suggest a wide tyramine safety margin for the selegiline transdermal system and provide evidence that the 6-mg/24-h selegiline transdermal system can be administered safely without dietary tyramine restrictions.

Effect of oral linezolid on the pressor response to intravenous tyramine

To investigate the effect of monoamine oxidase A inhibition from a single oral dose of linezolid on the pressor response to intravenous (i.v.) tyramine, using positive and negative controls to validate the methodology. This placebo-controlled, three-period crossover study was conducted in 12 healthy male volunteers. Each volunteer received either one oral dose of moclobemide (300 mg), linezolid (600 mg), or placebo tablet followed by an i.v. tyramine pressor test until an increase in systolic blood pressure of at least 30 mmHg above baseline occurred. Each study day was separated by a 7-day washout period. The dose of tyramine required to raise the blood pressure by 30 mmHg (TYR30) was calculated for each oral treatment by linear interpolation between log-transformed doses of i.v. tyramine. The influence of body mass index (BMI) on TYR30 was also investigated. The tyramine sensitivity factor (ratio of the geometric least square mean TYR30 for placebo and active oral treatment) was 1.8 [90% confidence interval (CI) 1.6, 2.0, P < 0.0001] for linezolid and 2.1 (90% CI 1.8, 2.4, P < 0.0001) for the positive control moclobemide. BMI had a statistically significant effect on TYR30. There was a significant difference in the pressor response to i.v. tyramine between linezolid and placebo. Moclobemide (positive control) and linezolid have a similar pressor response to i.v. tyramine. The statistically significant effect of BMI on TYR30 underlines the advantage of within-individual comparisons of treatments in order to reduce variability and provide more accurate treatment estimates.

Tyramine-Induced cardiac arrhythmias

Five out of 12 physically healthy patients with depression undergoing a tyramine pressor test developed cardiac arrhythmias. These arrhythmias occurred in drug-free patients in three out of 12 infusions following as little as 0.03 mg/kg of tyramine and after moclobemide, a reversible inhibitor of monoamine oxidase-A, in four out of 14 tyramine infusions with as little as 0.04 mg/kg of tyramine. The arrhythmias seen were independent of patient's age and occurred both before and after 30 mmHg elevations in systolic blood pressure. Electrocardiographic abnormalities and arrhythmias seen were a loss of p waves, sinus tachycardia, frequent atrial ectopic beats, atrial premature beats, Wenckebach phenomenon, junctional rhythm, ventricular ectopics, varying QRS configurations, and ventricular bigeminy. Tyramine, both oral and intravenous, caused similar reproducible changes in dogs, though not in rats, mice or guinea pigs. Practical implications are that tyramine pressor testing in humans should be performed cautiously and only with adequate cardiac monitoring and resuscitation facilities at hand. These findings suggest that a normal dietary component can induce serious cardiac arrhythmias, and that a low-tyramine diet may be of value for patients who are susceptible to cardiac arrhythmias.

Interaction between orally administered tyramine and moclobemide

This article describes a standardized oral tyramine pressor test designed to give information on safety aspects in the real everyday life situation where tyramine is ingested only with food. Results showed that significantly higher doses of tyramine were required to raise standing blood pressure by at least 30 mmHg (TYR 30) when it was taken with food than when subjects fasted. The same test was then conducted in 8 healthy volunteers during treatment with moclobemide 200 mg 3 times daily and tranylcypromine 10 mg 3 times daily. With moclobemide the mean TYR 30 dose was 306 mg, and the ratio of this to baseline was 5.0. With tranylcypromine, however, the mean TYR 30 dose was only 35 mg and the TSF ratio 38.2. The potentiation by tranylcypromine was thus 7.6 times greater than that of moclobemide. When tyramine was given in the food under treatment with MAO inhibitors, the TYR 30 doses were larger than those obtained under fasting conditions, but the TSF ratios were not altered. When the tyramine was given in a protein-rich or a lipid-rich meal, the previously established TYR 30 had significantly less effect on the blood pressure. The lowest TYR 30 dose during moclobemide treatment is at least 150 mg tyramine, an amount contained in about 300 g strong cheese or 100 g of yeast extract. These quantities are unlikely to be consumed in a normal meal. The corresponding TYR 30 dose for tranylcypromine, however, is only 20 mg tyramine, which can easily be contained in a fairly normal portion of strong cheese (40 g).(ABSTRACT TRUNCATED AT 250 WORDS)

Tyramine and New Monoamine Oxidase Inhibitor Drugs

The hypertensive crisis induced by the ingestion of cheese in subjects undergoing treatment with monoamine oxidase inhibitors (MAOIs) led to their virtual disappearance in many parts of the world. Three strategies to try and diminish the risk of this reaction have been developed: the combination of current (irreversible and non-selective) MAOIs with tricyclic antidepressants, the use of new selective MAOIs, and the use of new reversible MAOIs. The relative effectiveness of these different approaches can be assessed by the tyramine pressor test. The introduction of reversible and selective monoamine oxidase-A (MAO-A) inhibitors looks especially promising clinically.

Oral Tyramine Pressor Test and the Safety of Monoamine Oxidase Inhibitor Drugs

The pressor effect of orally administered tyramine (TYR) has been evaluated in 124 tests of 49 healthy unmedicated volunteers, in 99 tests of 29 subjects treated with the reversible selective monoamine oxidase (MAO) A inhibitor brofaromine (BROF), and in 73 tests of 12 subjects treated with tranylcypromine (TCP). In unmedicated subjects, pressor doses of TYR to raise systolic blood pressure (BP) by 30 mm Hg (PD30) ranged between 200 and 800 mg of TYR. There was no correlation of PD30 with sex, age, or weight. In repeated tests, the intraindividual coefficient of variation of the PD30 (+/- SD) was 10 +/- 9%. During treatment for 8 to 16 days with the two MAO inhibitors (MAOIs) BROF and TCP, seven-fold and 56-fold increases of TYR pressor sensitivity were estimated. A significant correlation was found between the individual PD30 before and during MAO inhibition with BROF. Cheese with a pressor content equal to the PD30 of TYR raised the systolic BP in only three of 10 volunteers during BROF inconsistently by not more than 20 mm. Therefore, the probability of "cheese reactions" during treatment with this reversible MAOI seems to be small. For complete normalization of oral pressor responsiveness, delays of 8 and 30 days after the last doses of BROF and TCP, respectively, are needed. The total incidence of systolic BP elevations by more than 60 mm Hg was 13% in a total of 296 oral tests given to 49 subjects. This incidence of easily controllable hypertensive reactions is outweighed by the importance of the test as predictor of clinical risks for drugs with TYR potentiating effects.

Results of an open clinical trial of brofaromine (CGP 11 305 A), a competitive, selective, and short-acting inhibitor of MAO-A in major endogenous depression.

In an open clinical trial the authors treated 18 hospitalized patients suffering from endogenous depression with brofaromine (CGP 11305A), a competitive, selective, and short-acting inhibitor of type A monoamine oxidase (MAO). Four patients were defined as good responders, as they had a final HAMD score of between 0 and 7 points. Four patients were judged as improved, with final HAMD scores of between 8 and 15 points, while the remaining eight patients failed to respond (final HAMD score greater than or equal to 16 points). The major observations were a beneficial influence on drive in most patients, while paranoid symptoms worsened markedly, rendering the substance contraindicated in psychotic depression. Brofaromine appears to be safe and well tolerated and largely free of side effects. As objectified by the tyramine pressor test, dietary restrictions during brofaromine treatment require less stringency than is the case with conventional MAO inhibitors. The specificity of brofaromine to inhibit deamination is limited to MAO-A, since no reduction in platelet MAO activity was measurable. Sleep EEG recordings in a subset of patients reveals that the amount of rapid eye movement (REM) sleep is significantly reduced during brofaromine treatment.

Correlations between serum ami- and nortriptyline concentrations and psychomotor performance.

Correlations of serum nortriptyline (NT) and amitriptyline (AT) levels with psychomotor performance choice reaction performance, eye-hand coordination, and divided attention was studied in two experiments each with 20 healthy subjects. In the first experiment serum NT level was measured with an isotope derivative method after treatment for 14 days with NT. In the second trial plasma AT and NT concentrations were measured with gas-chromatography after treatment for 14 days with AT. No linear correlations between the levels of the antidepressants and performance variables were found. Low levels of NT (less than 50 ng/ml) tended to shorten reaction time, and intermediate levels (50--80 ng/ml) to prolong it, when compared with the reaction times during placebo. The correlation between serum NT levels and the increase of the tyramine dose in the tyramine pressor test was not significant. A new assay method for AT and NT is presented.