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Drug Interactions between atropine / phenobarbital and thiotepa

This report displays the potential drug interactions for the following 2 drugs:

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Interactions between your drugs

Moderate

PHENobarbital thiotepa

Applies to: atropine / phenobarbital and thiotepa

GENERALLY AVOID: Coadministration with strong CYP450 3A4 inducers may decrease plasma concentrations of thiotepa and increase concentrations of its active metabolite triethylenephosphoramide (TEPA). Thiotepa is a prodrug that is primarily converted to TEPA by the isoenzyme. In a study involving a 42-year-old male with relapsing germ-cell cancer, the pharmacokinetics of thiotepa and its active metabolite (TEPA) were assessed during two high-dose chemotherapy courses (cyclophosphamide 1500 mg/m2/day, thiotepa 120 mg/m2/day, and carboplatin), with phenytoin initiated five days before the second course for seizure management. In the second course, TEPA exposure increased by 115% and thiotepa exposure decreased by 29%, resulting in a thiotepa dose reduction of nearly 40% on day 3 due to the increased risk of toxicity from higher TEPA exposure.

MANAGEMENT: Given the increased risk of toxicity, concomitant use of thiotepa with strong CYP450 3A4 inducers should generally be avoided. If coadministration with a strong CYP450 3A4 inducer is required a dose reduction may be considered. Patients should also be more closely monitored for thiotepa-related toxicities such as myelosuppression, cutaneous toxicity, and neurotoxicity. Pretreatment and subsequent blood counts may be used to guide dose adjustments in accordance with product labeling.

References (5)
  1. de Jonge ME, Huitema AD, van Dam SM, Beijnen JH, Rodenhuis S (2005) "Significant induction of cyclophosphamide and thiotepa metabolism by phenytoin." Cancer Chemother Pharmacol, 55, p. 507-10
  2. (2023) "Product Information. Thiotepa (thiotepa)." Meitheal Pharmaceuticals Inc.
  3. (2023) "Product Information. Tepadina (thiotepa)." Link Medical Products Pty Ltd T/A Link Pharmaceuticals, 3
  4. (2022) "Product Information. Thiotepa (thiotepa)." MSN Laboratories Europe Ltd
  5. (2021) "Product Information. Tepadina (thiotepa)." Adienne SA

Drug and food interactions

Major

PHENobarbital food

Applies to: atropine / phenobarbital

GENERALLY AVOID: Concurrent acute use of barbiturates and ethanol may result in additive CNS effects, including impaired coordination, sedation, and death. Tolerance of these agents may occur with chronic use. The mechanism is related to inhibition of microsomal enzymes acutely and induction of hepatic microsomal enzymes chronically.

MANAGEMENT: The combination of ethanol and barbiturates should be avoided.

References (5)
  1. Gupta RC, Kofoed J (1966) "Toxological statistics for barbiturates, other sedatives, and tranquilizers in Ontario: a 10-year survey." Can Med Assoc J, 94, p. 863-5
  2. Misra PS, Lefevre A, Ishii H, Rubin E, Lieber CS (1971) "Increase of ethanol, meprobamate and pentobarbital metabolism after chronic ethanol administration in man and in rats." Am J Med, 51, p. 346-51
  3. Saario I, Linnoila M (1976) "Effect of subacute treatment with hypnotics, alone or in combination with alcohol, on psychomotor skills related to driving." Acta Pharmacol Toxicol (Copenh), 38, p. 382-92
  4. Stead AH, Moffat AC (1983) "Quantification of the interaction between barbiturates and alcohol and interpretation of fatal blood concentrations." Hum Toxicol, 2, p. 5-14
  5. Seixas FA (1979) "Drug/alcohol interactions: avert potential dangers." Geriatrics, 34, p. 89-102
Moderate

atropine food

Applies to: atropine / phenobarbital

GENERALLY AVOID: Use of anticholinergic agents with alcohol may result in sufficient impairment of attention so as to render driving and operating machinery more hazardous. In addition, the potential for abuse may be increased with the combination. The mechanism of interaction is not established but may involve additive depressant effects on the central nervous system. No effect of oral propantheline or atropine on blood alcohol levels was observed in healthy volunteers when administered before ingestion of a standard ethanol load. However, one study found impairment of attention in subjects given atropine 0.5 mg or glycopyrrolate 1 mg in combination with alcohol.

MANAGEMENT: Alcohol should generally be avoided during therapy with anticholinergic agents. Patients should be counseled to avoid activities requiring mental alertness until they know how these agents affect them.

References (1)
  1. Linnoila M (1973) "Drug effects on psychomotor skills related to driving: interaction of atropine, glycopyrrhonium and alcohol." Eur J Clin Pharmacol, 6, p. 107-12

Therapeutic duplication warnings

No warnings were found for your selected drugs.

Therapeutic duplication warnings are only returned when drugs within the same group exceed the recommended therapeutic duplication maximum.

See also

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Drug Interaction Classification

These classifications are only a guideline. The relevance of a particular drug interaction to a specific individual is difficult to determine. Always consult your healthcare provider before starting or stopping any medication.
Major Highly clinically significant. Avoid combinations; the risk of the interaction outweighs the benefit.
Moderate Moderately clinically significant. Usually avoid combinations; use it only under special circumstances.
Minor Minimally clinically significant. Minimize risk; assess risk and consider an alternative drug, take steps to circumvent the interaction risk and/or institute a monitoring plan.
Unknown No interaction information available.

Further information

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