Drug General Information (ID: DDI1Z5RDSJ)
  Drug Name Thiethylperazine Drug Info Doxepin (topical) Drug Info
  Drug Type Small molecule Small molecule
  Therapeutic Class Antiemetics Antidepressants
  Structure

 Mechanism of Thiethylperazine-Doxepin (topical) Interaction (Severity Level: Moderate)
     Competitive inhibition of metabolic enzyme Click to Show/Hide Mechanism Graph
Could Not Find 2D Structure
      Drug Name Thiethylperazine Doxepin (topical)
      Mechanism CYP450 2D6 substrate CYP450 2D6 substrate
      Key Mechanism Factor 1
Factor Name Cytochrome P450 2D6
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Structure Sequence
MGLEALVPLAVIVAIFLLLVDLMHRRQRWAARYPPGPLPLPGLGNLLHVDFQNTPYCFDQLRRRFGDVFSLQLAWTPVVVLNGLAAVREALVTHGEDTADRPPVPITQILGFGPRSQGVFLARYGPAWREQRRFSVSTLRNLGLGKKSLEQWVTEEAACLCAAFANHSGRPFRPNGLLDKAVSNVIASLTCGRRFEYDDPRFLRLLDLAQEGLKEESGFLREVLNAVPVLLHIPALAGKVLRFQKAFLTQLDELLTEHRMTWDPAQPPRDLTEAFLAEMEKAKGNPESSFNDENLRIVVADLFSAGMVTTSTTLAWGLLLMILHPDVQRRVQQEIDDVIGQVRRPEMGDQAHMPYTTAVIHEVQRFGDIVPLGVTHMTSRDIEVQGFRIPKGTTLITNLSSVLKDEAVWEKPFRFHPEHFLDAQGHFVKPEAFLPFSAGRRACLGEPLARMELFLFFTSLLQHFSFSVPTGQPRPSHHGVFAFLVSPSPYELCAVPR
Gene Name CYP2D6
Uniprot ID CP2D6_HUMAN
KEGG Pathway hsa:1565
Protein Family Cytochrome P450 family
Protein Function
A cytochrome P450 monooxygenase involved in the metabolism of fatty acids, steroids and retinoids (PubMed:18698000, PubMed:19965576, PubMed:20972997, PubMed:21289075, PubMed:21576599). Mechanistically, uses molecular oxygen inserting one oxygen atom into a substrate, and reducing the second into a water molecule, with two electrons provided by NADPH via cytochrome P450 reductase (NADPH--hemoprotein reductase) (PubMed:18698000, PubMed:19965576, PubMed:20972997, PubMed:21289075, PubMed:21576599). Catalyzes the epoxidation of double bonds of polyunsaturated fatty acids (PUFA) (PubMed:19965576, PubMed:20972997). Metabolizes endocannabinoid arachidonoylethanolamide (anandamide) to 20-hydroxyeicosatetraenoic acid ethanolamide (20-HETE-EA) and 8,9-, 11,12-, and 14,15-epoxyeicosatrienoic acid ethanolamides (EpETrE-EAs), potentially modulating endocannabinoid system signaling (PubMed:18698000, PubMed:21289075). Catalyzes the hydroxylation of carbon-hydrogen bonds. Metabolizes cholesterol toward 25-hydroxycholesterol, a physiological regulator of cellular cholesterol homeostasis (PubMed:21576599). Catalyzes the oxidative transformations of all-trans retinol to all-trans retinal, a precursor for the active form all-trans-retinoic acid (PubMed:10681376). Also involved in the oxidative metabolism of drugs such as antiarrhythmics, adrenoceptor antagonists, and tricyclic antidepressants.
    Click to Show/Hide
      Mechanism Description
  • Increased plasma concentrations of Thiethylperazine and Doxepin (topical) due to competitive inhibition of the same metabolic pathway

Recommended Action
      Management Concurrent use of phenothiazines and TCAs should be approached with caution, particularly in the elderly and those with underlying organic brain disease, who tend to be more sensitive to the central anticholinergic effects of these drugs and in whom toxicity symptoms may be easily overlooked. Patients should be advised to notify their physician promptly if they experience potential symptoms of anticholinergic intoxication (e.g., abdominal pain, fever, heat intolerance, blurred vision, confusion, hallucinations) or cardiovascular toxicity (e.g., dizziness, palpitations, arrhythmias, syncope). Ambulatory patients should be counseled to avoid activities requiring mental alertness until they know how these agents affect them.

References
1 Lee BS "Possibility of hyperpyrexia with antipsychotic and anticholinergic drugs." J Clin Psychiatry 47 (1986): 571. [PMID: 3771507]
2 Siris SG, Cooper TB, Rifkin AE, Brenner R, Lieberman JA "Plasma imipramine concentrations in patients receiving concomitant fluphenazine decanoate." Am J Psychiatry 139 (1982): 104-6. [PMID: 7055248]
3 Vandel S, Sandoz M, Vandel B, Bonin B, Allers G, Volmat R "Biotransformation of amitriptyline in man: interaction with phenothiazines." Neuropsychobiology 15 (1986): 15-9. [PMID: 2873526]