Phenylpropanolamine increases plasma caffeine levels

Mixed lactate and caffeine compound increases satellite cell activity and anabolic signals for muscle hypertrophy

We examined whether a mixed lactate and caffeine compound (LC) could effectively elicit proliferation and differentiation of satellite cells or activate anabolic signals in skeletal muscles. We cultured C2C12 cells with either lactate or LC for 6 h. We found that lactate significantly increased myogenin and follistatin protein levels and phosphorylation of P70S6K while decreasing the levels of myostatin relative to the control. LC significantly increased protein levels of Pax7, MyoD, and Ki67 in addition to myogenin, relative to control. LC also significantly increased follistatin expression relative to control and stimulated phosphorylation of mTOR and P70S6K. In an in vivo study, male F344/DuCrlCrlj rats were assigned to control (Sed, n = 10), exercise (Ex, n = 12), and LC supplementation (LCEx, n = 13) groups. LC was orally administered daily. The LCEx and Ex groups were exercised on a treadmill, running for 30 min at low intensity every other day for 4 wk. The LCEx group experienced a significant increase in the mass of the gastrocnemius (GA) and tibialis anterior (TA) relative to both the Sed and Ex groups. Furthermore, the LCEx group showed a significant increase in the total DNA content of TA compared with the Sed group. The LCEx group experienced a significant increase in myogenin and follistatin expression of GA relative to the Ex group. These results suggest that administration of LC can effectively increase muscle mass concomitant with elevated numbers of myonuclei, even with low-intensity exercise training, via activated satellite cells and anabolic signals.

Dispositional study of opioids in mice pretreated with sympathomimetic agents

Brain and plasma levels of morphine and codeine were determined by an assay method involving solid-phase extraction and ion-pair reversed phase HPLC. Detection was by a variable wavelength UV-detector (for codeine) and an amperometric electrochemical detector (for morphine) coupled in series. Ephedrine or phenylpropanolamine pretreatment did not interfere with the plasma disposition of morphine, evidenced by overlapping plasma concentration-time profiles. Brain opioid levels were equally unaffected by sympathomimetic pretreatment. The relative ratios of brain to plasma concentrations at the time corresponding to the respective peak anti-nociceptive activity for morphine and codeine revealed no significant differences. It is concluded that single doses of ephedrine and phenylpropanolamine do not affect the disposition of morphine and codeine in mice.

Absence of QTc-Interval-Prolonging or Hemodynamic Effects of a Single Dose of Bitter-Orange Extract in Healthy Subjects

STUDY OBJECTIVE

To evaluate the hemodynamic and electrocardiographic effects of a single dose of commercially available bitter-orange dried-fruit extract, which is increasingly being used in dietary supplements.

DESIGN

Randomized, double-blind, placebo-controlled, crossover study.

SETTING

University of Connecticut, Storrs Campus.

SUBJECTS

Eighteen healthy volunteers aged 18 years or older.

INTERVENTION

Subjects were given either placebo or bitter-orange dried-fruit extract (450 mg standardized to 27 mg of m- or p-synephrine) in phase 1. The opposite treatment was given during phase 2 after a washout period of at least 7 days.

MEASUREMENTS AND MAIN RESULTS

The rate-corrected QT (QTc) interval and blood pressure were measured before dosing and at 1, 3, 5, and 8 hours after dosing. Mean+/-SD values of the maximum postdose values were compared between groups. Subjects receiving bitter-orange extract versus those receiving placebo had similar postdose QTc intervals (402+/-29 vs 403+/-24 msec, p=0.653), systolic blood pressure (114+/-10 vs 115+/-8 mm Hg, p=0.686) and diastolic blood pressure (68+/-9 vs 68+/-8, p=0.879).

CONCLUSION

Bitter-orange dried-fruit extract standardized to m- or p-synephrine 27 mg did not significantly alter the QTc interval or blood pressure after a single dose was administered. Future studies are necessary to ensure the safety of this herbal product with multiple doses.

Electrocardiographic effects of an Ephedra-Free, multicomponent weight-loss supplement in healthy volunteers

STUDY OBJECTIVE

Metabolife 356, an ephedra-containing weight-loss product, substantially increases the corrected QT (QTc) interval. Metabolife Ephedra Free, a similar supplement, contains caffeine and extracts of green tea, garcinia cambogia, and yerba mate. Its electrocardiographic (ECG) effects are not known. Therefore, we sought to determine the effect of this supplement on the QTc interval.

DESIGN

Randomized, double-blind, placebo-controlled, crossover study.

SETTING

University of Connecticut, Storrs Campus.

SUBJECTS

Twenty healthy volunteers. Intervention. A single capsule containing half the normal recommended dose of Metabolife Ephedra Free or matching placebo was administered in crossover fashion, with a 7-day washout period between treatments.

MEASUREMENTS AND MAIN RESULTS

Baseline and three postdose ECG measurements were obtained, and QTc intervals were measured over a 5-hour study period. No significant differences in the QTc interval or other ECG variables were observed between the Metabolife Ephedra Free and placebo groups.

CONCLUSION

At half the recommended single dose, Metabolife Ephedra Free does not affect the QTc interval or other ECG variables over 5 hours. Dose-response studies and studies of longer duration should be conducted.

Pharmacokinetic interactions between phenylpropanolamine, caffeine and chlorpheniramine in rats

As the mechanism involved in the serious adverse effects associated with phenylpropanolamine (PPA) has not yet been clarified, and as PPA in usual cases is not being ingested without other drugs combination, the aim of this study was to characterize the possibility of pharmacokinetic interactions between PPA and most often combined drugs existing in the same dosage. The pharmacokinetics of PPA in rat brain and blood were evaluated when administered alone (group I), combined with caffeine (group II), combined with chlorpheniramine (group III), combined with both caffeine and chlorpheniramine (group IV) and finally when existed in one of the available OTC products (group V). This product contains multiple ingredients of PPA, caffeine and chlorpheniramine. In brain the pharmacokinetic parameters of PPA were significantly affected with the combined administration of caffeine and/or chlorpheniramine. The single intraperitoneal administration of caffeine (5 mg/kg) with PPA (2.5 mg/kg) to rats caused 1.6-fold increase in the AUC of PPA in brain compared to the single administration of PPA, and was comparable to the 1.5-fold increase caused by chlorpheniramine (0.4 mg/kg). The multiple combinations caused an increase in the AUC by 1.9-fold, which is comparable to the increase in the AUC of PPA obtained from the OTC product (2.2-fold). On the other hand, there was no significant difference in the pharmacokinetics of PPA in blood between the groups except for the C(max) of PPA in groups I and IV. The observed adverse effects associated with PPA use could be related to the significant increase in its levels in the brain.

Clinically significant pharmacokinetic interactions between dietary caffeine and medications

Caffeine from dietary sources (mainly coffee, tea and soft drinks) is the most frequently and widely consumed CNS stimulant in the world today. Because of its enormous popularity, the consumption of caffeine is generally thought to be safe and long term caffeine intake may be disregarded as a medical problem. However, it is clear that this compound has many of the features usually associated with a drug of abuse. Furthermore, physicians should be aware of the possible contribution of dietary caffeine to the presenting signs and symptoms of patients. The toxic effects of caffeine are extensions of their pharmacological effects. The most serious caffeine-related CNS effects include seizures and delirium. Other symptoms affecting the cardiovascular system range from moderate increases in heart rate to more severe cardiac arrhythmia. Although tolerance develops to many of the pharmacological effects of caffeine, tolerance may be overwhelmed by the nonlinear accumulation of caffeine when its metabolism becomes saturated. This might occur with high levels of consumption or as the result of a pharmacokinetic interaction between caffeine and over-the-counter or prescription medications. The polycyclic aromatic hydrocarbon-inducible cytochrome P450 (CYP) 1A2 participates in the metabolism of caffeine as well as of a number of clinically important drugs. A number of drugs, including certain selective serotonin reuptake inhibitors (particularly fluvoxamine), antiarrhythmics (mexiletine), antipsychotics (clozapine), psoralens, idrocilamide and phenylpropanolamine, bronchodilators (furafylline and theophylline) and quinolones (enoxacin), have been reported to be potent inhibitors of this isoenzyme. This has important clinical implications, since drugs that are metabolised by, or bind to, the same CYP enzyme have a high potential for pharmacokinetic interactions due to inhibition of drug metabolism. Thus, pharmacokinetic interactions at the CYP1A2 enzyme level may cause toxic effects during concomitant administration of caffeine and certain drugs used for cardiovascular, CNS (an excessive dietary intake of caffeine has also been observed in psychiatric patients), gastrointestinal, infectious, respiratory and skin disorders. Unless a lack of interaction has already been demonstrated for the potentially interacting drug, dietary caffeine intake should be considered when planning, or assessing response to, drug therapy. Some of the reported interactions of caffeine, irrespective of clinical relevance, might inadvertently cause athletes to exceed the urinary caffeine concentration limit set by sports authorities at 12 mg/L. Finally, caffeine is a useful and reliable probe drug for the assessment of CYP1A2 activity, which is of considerable interest for metabolic studies in human populations.

Over-the-counter stimulants: abuse and addiction

A widely held belief is that amphetamine-like stimulants have abuse potential, but addiction to these drugs is seldom mentioned. We describe seven patients who fulfilled criteria for amphetamine-like abuse or dependence, based on the fourth edition of the Diagnostic and Statistical Manual of Mental Disorders. This case series lends clinical support to the research findings that amphetamine-like drugs are reinforcing and therefore can be addictive. The use of standardized criteria to classify excessive over-the-counter stimulant use as abuse or dependence distinguishes these case reports from others in the medical literature. Public concern about the misuse of this class of drugs is discussed. We propose that clinicians use standardized criteria to diagnose accurately abuse of or dependence on over-the-counter stimulants for a better understanding of the extent of this problem.

Caffeine test assessment for measuring liver function in critically ill patients

Caffeine elimination was studied in 73 patients admitted to an intensive care unit, 33 of whom had liver disease. Mean plasma clearance of caffeine in patients with no liver disease (1.30 +/- 0.79 ml/kg/min) was significantly higher than in patients with liver disease (0.39 +/- 0.23 ml/kg/min). Mean half-life of caffeine in patients with liver disease (23.96 +/- 12.19 h) was significantly higher than in patients with no liver disease (7.25 +/- 3.04 h). No significant differences in distribution volumes were found. Receptor-operator curves (ROC) for plasma clearance and the half-life of elimination of caffeine showed a high diagnostic value. Therefore, the parameters for caffeine biotransformation, i.e. Cl and t1/2, are useful for assessing liver function in the population studied.

The discriminative stimulus properties of legal, over-the-counter stimulants administered singly and in binary and ternary combinations

Ninety-six male Sprague-Dawley rats were trained in one of seven drug versus saline (SAL) discrimination (DD) tasks under a variable-ratio 5-15 schedule of food-motivated lever press responding. Three groups of rats (n = 12/group) were trained to discriminate between one of the legal over-the-counter (OTC) stimulants--caffeine (CAF), ephedrine (EPHED), phenylpropanolamine (PPA), and SAL. Three other groups (n = 12/group) were trained to discriminate between one of three binary stimulant combinations--CAF+EPHED, CAF+PPA, EPHED+PPA, and SAL. The seventh group of rats (n = 24) was trained to discriminate between SAL and a ternary combination of the OTC stimulants, CAF+EPHED+PPA. Generalization tests were conducted with each of the OTC stimulants and the controlled stimulants--amphetamine (AMPHET) and cocaine (COC). The data suggest: 1) there is cross-generalization between some OTC combinations and controlled stimulants; 2) full generalization between the OTC and controlled stimulants were demonstrated in rats trained to discriminate two of the binary stimulant combinations from SAL; 3) drug mixtures are not perceived as new entities distinct from their component elements; 4) training dose-ratio may influence the characteristics of mixture discriminations; 5) stimulus overshadowing may be a factor determining drug mixture cues, and 6) the DD properties of aggregate drug compounds may function within a euclidean metric space. We propose that some binary OTC stimulant combinations may effectively function as a methadone-like replacement therapy in cocaine dependence.

Caffeine and the central nervous system: mechanisms of action, biochemical, metabolic and psychostimulant effects

Caffeine is the most widely consumed central-nervous-system stimulant. Three main mechanisms of action of caffeine on the central nervous system have been described. Mobilization of intracellular calcium and inhibition of specific phosphodiesterases only occur at high non-physiological concentrations of caffeine. The only likely mechanism of action of the methylxanthine is the antagonism at the level of adenosine receptors. Caffeine increases energy metabolism throughout the brain but decreases at the same time cerebral blood flow, inducing a relative brain hypoperfusion. Caffeine activates noradrenaline neurons and seems to affect the local release of dopamine. Many of the alerting effects of caffeine may be related to the action of the methylxanthine on serotonin neurons. The methylxanthine induces dose-response increases in locomotor activity in animals. Its psychostimulant action on man is, however, often subtle and not very easy to detect. The effects of caffeine on learning, memory, performance and coordination are rather related to the methylxanthine action on arousal, vigilance and fatigue. Caffeine exerts obvious effects on anxiety and sleep which vary according to individual sensitivity to the methylxanthine. However, children in general do not appear more sensitive to methylxanthine effects than adults. The central nervous system does not seem to develop a great tolerance to the effects of caffeine although dependence and withdrawal symptoms are reported.

Dose-dependent response to phenylpropanolamine: inhibition of orthostasis

Phenylpropanolamine, a widely consumed over-the-counter drug, is known to elevate blood pressure, but the mechanism is unknown; it may be both a direct and indirect sympathomimetic. This study investigated the effects of 75-mg sustained-release phenylpropanolamine, 75-mg phenylpropanolamine plus 400-mg caffeine, and 150-mg phenylpropanolamine on blood pressure, plasma norepinephrine, and epinephrine levels in 16 normotensive subjects in a double-blind, placebo-controlled crossover design. Mean peak phenylpropanolamine levels of 317 +/- 26, 152 +/- 17, and 157 +/- 17 ng/mL for 150-mg phenylpropanolamine, 75-mg phenylpropanolamine, and 75-mg phenylpropanolamine plus 400-mg caffeine, respectively, were reached at about 3.6 hours after dosing. The maximal increases in supine diastolic blood pressures after all three phenylpropanolamine-containing drugs were almost three times that after placebo (P less than .05), but peak blood pressures occurred at about 2.3 hours earlier than peak phenylpropanolamine levels. Blood pressure increases correlated with phenylpropanolamine plasma levels (r = .49 for systolic blood pressure and r = .34 for diastolic blood pressure; P less than .0001 for both). Norepinephrine levels increased after the administration of 150-mg phenylpropanolamine and 75-mg phenylpropanolamine plus 400-mg caffeine; norepinephrine increases correlated with phenylpropanolamine levels (r = .34, P less than .0001). The expected increment in norepinephrine induced by standing was significantly decreased by phenylpropanolamine in a dose-dependent mode. The study supports the idea that phenylpropanolamine as both a direct (at alpha -1 and alpha-2 receptors) and an indirect sympathomimetic agent.