Although not specifically identified in studies with tinidazole, the following drug interactions were reported for metronidazole, a chemically-related nitroimidazole. Therefore, these drug interactions may occur with tinidazole.
Potential effects of tinidazole on other drugs
Warfarin and other oral coumarin anticoagulants
As with metronidazole, tinidazole may enhance the effect of warfarin and other coumarin anticoagulants, resulting in a prolongation of prothrombin time. The dosage of oral anticoagulants may need to be adjusted during tinidazole co-administration and up to 8 days after discontinuation.
Alcohols, disulfiram
Alcoholic beverages and preparations containing ethanol or propylene glycol should be avoided during tinidazole therapy and for 3 days afterward because abdominal cramps, nausea, vomiting, headaches, and flushing may occur. Psychotic reactions have been reported in alcoholic patients using metronidazole and disulfiram concurrently. Though no similar reactions have been reported with tinidazole, tinidazole should not be given to patients who have taken disulfiram within the last two weeks.
Lithium
Metronidazole has been reported to elevate serum lithium levels. It is not known if tinidazole shares this property with metronidazole, but consideration should be given to measuring serum lithium and creatinine levels after several days of simultaneous lithium and tinidazole treatment to detect potential lithium intoxication.
Phenytoin, fosphenytoin
Concomitant administration of oral metronidazole and intravenous phenytoin was reported to result in prolongation of the half-life and reduction in the clearance of phenytoin. Metronidazole did not significantly affect the pharmacokinetics of orally-administered phenytoin.
Cyclosporine, tacrolimus
There are several case reports suggesting that metronidazole has the potential to increase the levels of cyclosporine and tacrolimus. During tinidazole coadministration with either of these drugs, the patient should be monitored for signs of calcineurin-inhibitor associated toxicities.
Fluorouracil
Metronidazole was shown to decrease the clearance of fluorouracil, resulting in an increase in side-effects without an increase in therapeutic benefits. If the concomitant use of tinidazole and fluorouracil cannot be avoided, the patient should be monitored for fluorouracil-associated toxicities.
Potential effects of other drugs on tinidazole
CYP3A4 inducers and inhibitors
Simultaneous administration of tinidazole with drugs that induce liver microsomal enzymes, i.e., CYP3A4 inducers such as phenobarbital, rifampin, phenytoin, and fosphenytoin (a pro-drug of phenytoin), may accelerate the elimination of tinidazole, decreasing the plasma level of tinidazole. Simultaneous administration of drugs that inhibit the activity of liver microsomal enzymes, i.e., CYP3A4 inhibitors such as cimetidine and ketoconazole, may prolong the half-life and decrease the plasma clearance of tinidazole, increasing the plasma concentrations of tinidazole.
Cholestyramine
Cholestyramine was shown to decrease the oral bioavailability of metronidazole by 21%. Thus, it is advisable to separate dosing of cholestyramine and tinidazole to minimize any potential effect on the oral bioavailability of tinidazole.
Oxytetracycline
Oxytetracycline was reported to antagonize the therapeutic effect of metronidazole.
Laboratory test interactions
Tinidazole, like metronidazole, may interfere with certain types of determinations of serum chemistry values, such as aspartate aminotransferase (AST, SGOT), alanine aminotransferase (ALT, SGPT), lactate dehydrogenase (LDH), triglycerides, and hexokinase glucose. Values of zero may be observed. All of the assays in which interference has been reported involve enzymatic coupling of the assay to oxidation-reduction of nicotinamide adenine dinucleotide (NAD+ ↔ NADH). Potential interference is due to the similarity of absorbance peaks of NADH and tinidazole.
Tinidazole, like metronidazole, may produce transient leukopenia and neutropenia; however, no persistent hematological abnormalities attributable to tinidazole have been observed in clinical studies. Total and differential leukocyte counts are recommended if retreatment is necessary.
Important Safety Information
WARNING: POTENTIAL RISK FOR CARCINOGENICITY
Carcinogenicity has been seen in mice and rats treated chronically with metronidazole, another nitroimidazole agent. Although such data have not been reported for tinidazole, the two drugs are structurally related and have similar biologic effects. Its use should be reserved for the conditions described in INDICATIONS AND USAGE.
Tindamax® is a prescription antibiotic used to treat certain infections caused by bacteria and parasites. It is approved for treating trichomoniasis, also known as "trich," and bacterial vaginosis, or "BV" (in non-pregnant, adult women). It is also approved for treating giardiasis, also known as "giardia," amebiasis, and amebic liver abscess in patients age 3 and older.
Important Safety Information
Tindamax® is not for everyone. You should not take Tindamax® if you are in the first trimester of pregnancy. If you are nursing, Tindamax® can pass through your breast milk, so you should not take it unless you stop breastfeeding during your prescription and for 3 days after your last dose.
Tindamax® can lead to a temporary reduction in your white blood cells, so if you have been diagnosed with a blood disorder, talk to your doctor before starting a prescription.
Do not take Tindamax® if you have a history of sensitivity to tinidazole or related drugs in the nitroimidazole family. Reactions can range from mild itching, hives, or fever to Stevens-Johnson syndrome, which is a rare, life-threatening skin condition.
Certain drugs may interact with Tindamax®, so always tell your doctor about the medications you're taking before you start a prescription.
Take each dose of Tindamax® with food to lessen the risk of stomach upset and other GI side effects. Avoid any alcoholic beverages while taking Tindamax® and for 3 days afterward.
If you are undergoing hemodialysis while taking Tindamax® on the same day, consult your doctor for the appropriate dose of Tindamax®. An additional half-dose of Tindamax® at the end of dialysis may be recommended.
Antibacterial drugs, including Tindamax®, do not treat viral infections such as the common cold. When taking Tindamax® to treat a bacterial infection, it is very common to feel better early in your prescription; however, you should keep taking the medication as directed and for as long as directed by your doctor. Skipping doses or not taking all of your medication can make Tindamax® less effective. It can also allow the bacteria to build up resistance to the drug, so that it won't be treatable with Tindamax® or similar drugs in the future.
The most common side effects of Tindamax® are a metallic or bitter taste, nausea, weakness, fatigue, discomfort, indigestion, cramps, vomiting, loss of appetite, headache, dizziness, and constipation.
Some patients taking Tindamax® may also develop a yeast infection, which can require treatment with an anti-fungal drug. Talk to your doctor if you notice any unusual symptoms.
Certain patients taking Tindamax® have experienced seizures or nerve problems, with symptoms such as numbness or tingling of the hands or feet. Other side effects included vertigo, unsteady movements, insomnia, or drowsiness. Stop taking Tindamax® if you develop any abnormal symptoms.
Tinidazole, the key ingredient in Tindamax®, is related to a drug called metronidazole, which has been linked to cancer in lab rats and mice that received the drug over long periods of time. Although these effects have not been reported for tinidazole, the two drugs are chemically related and have similar effects on the body. Therefore, Tindamax® should only be used to treat infections it has been approved to treat.
To report negative side effects, contact Mission Pharmacal Company at 1-800-298-1087 or the FDA at 1-800-FDA-1088 or www.fda.gov/medwatch.
