Drug Interaction Report

MONITOR: Central nervous system- and/or respiratory-depressant effects may be additively or synergistically increased in patients taking multiple drugs that cause these effects, especially in elderly or debilitated patients. Sedation and impairment of attention, judgment, thinking, and psychomotor skills may increase.

MANAGEMENT: During concomitant use of these drugs, patients should be monitored for potentially excessive or prolonged CNS and respiratory depression. Cautious dosage titration may be required, particularly at treatment initiation. Ambulatory patients should be counseled to avoid hazardous activities requiring mental alertness and motor coordination until they know how these agents affect them, and to notify their physician if they experience excessive or prolonged CNS effects that interfere with their normal activities.

ADJUST DOSING INTERVAL: Alkalinization of the urine may decrease the plasma concentration of some tetracyclines. The mechanism is not completely understood, but may involve increased renal elimination of tetracyclines when the urine becomes alkalinized. Information is available for doxycycline, tetracycline, and sodium bicarbonate only.

MANAGEMENT: If these drugs must be used together, an alternating dosing schedule is recommended (three to four hours apart).

GENERALLY AVOID: Alcohol may potentiate some of the pharmacologic effects of CNS-active agents. Use in combination may result in additive central nervous system depression and/or impairment of judgment, thinking, and psychomotor skills.

MANAGEMENT: Patients receiving CNS-active agents should be warned of this interaction and advised to avoid or limit consumption of alcohol. Ambulatory patients should be counseled to avoid hazardous activities requiring complete mental alertness and motor coordination until they know how these agents affect them, and to notify their physician if they experience excessive or prolonged CNS effects that interfere with their normal activities.

GENERALLY AVOID: Ethanol may potentiate the central nervous system (CNS) depressant effects of opioid analgesics. Concomitant use may result in additive CNS depression and impairment of judgment, thinking, and psychomotor skills. In more severe cases, hypotension, respiratory depression, profound sedation, coma, or even death may occur.

MANAGEMENT: Concomitant use of opioid analgesics with ethanol should be avoided.

GENERALLY AVOID: The oral bioavailability of quinolone and tetracycline antibiotics may be reduced by concurrent administration of preparations containing polyvalent cations such as aluminum, calcium, iron, magnesium, and zinc. Therapeutic failure may result. The proposed mechanism is chelation of quinolone and tetracycline antibiotics by di- and trivalent cations, forming an insoluble complex that is poorly absorbed from the gastrointestinal tract. Reduced gastrointestinal absorption of the cations should also be considered.

MANAGEMENT: Concomitant administration of oral quinolone and tetracycline antibiotics with preparations containing aluminum, calcium, iron, magnesium, and/or zinc salts should generally be avoided. Otherwise, the times of administration should be staggered by as much as possible to minimize the potential for interaction. Quinolones should typically be dosed either 2 to 4 hours before or 4 to 6 hours after polyvalent cation preparations, depending on the quinolone and formulation. Likewise, tetracyclines and polyvalent cation preparations should typically be administered 2 to 4 hours apart. The prescribing information for the antibiotic should be consulted for more specific dosing recommendations.

MONITOR: Coadministration of two or more sympathomimetic agents may increase the risk of adverse effects such as nervousness, irritability, and increased heart rate. Central nervous system (CNS) stimulants, particularly amphetamines, can potentiate the adrenergic response to vasopressors and other sympathomimetic agents. Additive increases in blood pressure and heart rate may occur due to enhanced peripheral sympathetic activity.

MANAGEMENT: Caution is advised if two or more sympathomimetic agents are coadministered. Pulse and blood pressure should be closely monitored.