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Drug Interactions between atropine / phenobarbital and vandetanib

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

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Interactions between your drugs

Moderate

PHENobarbital vandetanib

Applies to: atropine / phenobarbital and vandetanib

GENERALLY AVOID: Coadministration with potent inducers of CYP450 3A4 may decrease the plasma concentrations of vandetanib, which is a substrate of the isoenzyme. In 16 healthy male subjects, coadministration of rifampin (600 mg/day on days 1 to 31) and vandetanib (single 300 mg oral dose on day 10) resulted in an approximately 40% decrease in vandetanib exposure (AUC) and almost 50% decrease in half-life (from 217.6 hours to 116.3 hours) compared to vandetanib administered alone. There was no significant change in the peak plasma concentration (Cmax) of vandetanib. In the presence of rifampin, the Cmax and AUC of a metabolite, N-desmethylvandetanib, increased by 414% and 266%, respectively. Rifampin also increased the Cmax and AUC of another metabolite, vandetanib N-oxide, by approximately 179% and 126%, respectively. However, the plasma concentrations of vandetanib N-oxide were very low throughout, thus the change in absolute plasma levels induced by rifampin was actually quite small. The clinical implications of these changes are unknown. The two metabolites have shown in vitro pharmacologic activity in cellular assays against vascular endothelial growth factor and epidermal growth factor, with N-desmethylvandetanib exhibiting similar potency to parent drug and vandetanib N-oxide exhibiting less than 1/50 the activity of the parent drug.

MANAGEMENT: Concomitant use of vandetanib with potent CYP450 3A4 inducers should generally be avoided.

References

  1. Martin P, Oliver S, Robertson J, Kennedy SJ, Read J, Duvauchelle T (2011) "Pharmacokinetic drug interactions with vandetanib during cadministration with rifampicin or itraconazole." Drugs R D, 11, p. 37-51
  2. (2011) "Product Information. Vandetanib (vandetanib)." Astra-Zeneca Pharmaceuticals

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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

  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
View all 5 references

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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. 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

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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

Always consult your healthcare provider to ensure the information displayed on this page applies to your personal circumstances.

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