Drug Interaction Report

Using dextromethorphan together with doxylamine may increase side effects such as dizziness, drowsiness, confusion, and difficulty concentrating. Some people, especially the elderly, may also experience impairment in thinking, judgment, and motor coordination. You should avoid or limit the use of alcohol while being treated with these medications. Also avoid activities requiring mental alertness such as driving or operating hazardous machinery until you know how the medications affect you. Talk to your doctor if you have any questions or concerns. It is important to tell your doctor about all other medications you use, including vitamins and herbs. Do not stop using any medications without first talking to your doctor.

Consumer information for this interaction is not currently available.

MONITOR: Coadministration with maribavir may increase the plasma concentrations of drugs that are substrates of the P-glycoprotein (P-gp) and/or breast cancer resistance protein (BCRP) efflux transporters, both of which have been shown to be inhibited in vitro by maribavir at clinically relevant concentrations. Inhibition of transporter-mediated efflux in the intestine and possibly other organs such as the liver and kidney can increase the systemic bioavailability and decrease the clearance of affected substrates. When a single 0.5 mg dose of digoxin, a sensitive P-gp substrate, was coadministered with maribavir 400 mg twice daily in 18 study subjects, mean digoxin peak plasma concentration (Cmax) and systemic exposure (AUC) increased by 25% and 21%, respectively, compared to digoxin administered alone. There are no clinical data regarding the use of maribavir with BCRP substrates, but increases in plasma concentrations of sensitive substrates such as rosuvastatin are expected according to the prescribing information.

MANAGEMENT: Caution is advised when maribavir is prescribed with drugs that are P-gp and/or BCRP substrates, particularly sensitive substrates or those with a narrow therapeutic range. Clinical and laboratory monitoring as well as dosage adjustments may be appropriate for some drugs whenever maribavir is added to or withdrawn from therapy. The prescribing information for concomitant medications should be consulted to assess the benefits versus risks of coadministration of P-gp/BCRP inhibitors and for any dosage adjustments that may be required.

Ask your doctor before using acetaminophen together with ethanol (alcohol). This can cause serious side effects that affect your liver. Call your doctor immediately if you experience a fever, chills, joint pain or swelling, excessive tiredness or weakness, unusual bleeding or bruising, skin rash or itching, loss of appetite, nausea, vomiting, or yellowing of the skin or the whites of your eyes. If your doctor does prescribe these medications together, you may need a dose adjustment or special tests to safely take both medications. It is important to tell your doctor about all other medications you use, including vitamins and herbs. Do not stop using any medications without first talking to your doctor.

Alcohol can increase the nervous system side effects of dextromethorphan such as dizziness, drowsiness, and difficulty concentrating. Some people may also experience impairment in thinking and judgment. You should avoid or limit the use of alcohol while being treated with dextromethorphan. Do not use more than the recommended dose of dextromethorphan, and avoid activities requiring mental alertness such as driving or operating hazardous machinery until you know how the medication affects you. Talk to your doctor or pharmacist if you have any questions or concerns.

Alcohol can increase the nervous system side effects of doxylamine such as dizziness, drowsiness, and difficulty concentrating. Some people may also experience impairment in thinking and judgment. You should avoid or limit the use of alcohol while being treated with doxylamine. Do not use more than the recommended dose of doxylamine, and avoid activities requiring mental alertness such as driving or operating hazardous machinery until you know how the medication affects you. Talk to your doctor or pharmacist if you have any questions or concerns.

Both pseudoephedrine and caffeine can increase blood pressure and heart rate, and combining them may enhance these effects. Talk to your doctor before using these medications, especially if you have a history of high blood pressure or heart disease. You may need a dose adjustment or more frequent monitoring by your doctor to safely use both medications. Contact your doctor if your condition changes or you experience increased side effects. It is important to tell your doctor about all other medications you use, including vitamins and herbs. Do not stop using any medications without first talking to your doctor.

Consumer information for this interaction is not currently available.

MONITOR: Smoking cessation may lead to elevated plasma concentrations and enhanced pharmacologic effects of drugs that are substrates of CYP450 1A2 (and possibly CYP450 1A1) and/or certain drugs with a narrow therapeutic index (e.g., flecainide, pentazocine). One proposed mechanism is related to the loss of CYP450 1A2 and 1A1 induction by polycyclic aromatic hydrocarbons in tobacco smoke; when smoking cessation agents are initiated and smoking stops, the metabolism of certain drugs may decrease leading to increased plasma concentrations. The mechanism by which smoking cessation affects narrow therapeutic index drugs that are not known substrates of CYP450 1A2 or 1A1 is unknown. The clinical significance of this interaction is unknown as clinical data are lacking.

MANAGEMENT: Until more information is available, caution is advisable if smoking cessation agents are used concomitantly with drugs that are substrates of CYP450 1A2 or 1A1 and/or those with a narrow therapeutic range. Patients receiving smoking cessation agents may require periodic dose adjustments and closer clinical and laboratory monitoring of medications that are substrates of CYP450 1A2 or 1A1.