- Molecular NameDiphenhydramine
- SynonymDiphenhydramine Base; Diphenhydramine Hcl; Diphenhydramine Salicylate; Diphenylhydramine
- Weight255.361
- Drugbank_IDDB01075
- ACS_NO58-73-1
- Show 2D model
- LogP (experiment)3.4
- LogP (predicted, AB/LogP v2.0)3.87
- pka9.0
- LogD (pH=7, predicted)2.18
- Solubility (experiment)1 g/ml
- LogS (predicted, ACD/Labs)(ph=7)-1.11
- LogSw (predicted, AB/LogsW2.0)0.17
- Sw (mg/ml) (predicted, ACD/Labs)0.38
- No.of HBond Donors0
- No.of HBond Acceptors2
- No.of Rotatable Bonds6
- TPSA12.47
- StatusFDA approved
- AdministrationOral, parenteral (IM), parenteral (IV), topical, suppository
- PharmacologyA first generation antihistamine mainly used to treat allergies and may act as an antiemetic, sedative and hypnotic.
- Absorption_valueN/A
- Absorption (description)Readily absorbed after oral administration
- Caco_2N/A
- Bioavailability61.0
- Protein binding98.5
- Volume of distribution (VD)4.5 L/kg
- Blood/Plasma Partitioning ratio (D_blood)Plasma:whole blood ratio, about 1.3.
- MetabollsmVarious cytochrome P450 liver enzymes: CYP2D6 (80%), 3A4 (10%). Undergoes extensive first-pass metabolism by N-dealkylation and oxidative deamination to form monodesmethyl and didesmethyl metabolites, and diphenylmethoxyacetic acid which may be conjugated with glutamine or glycine.
- Half life8.5 h
- ExcretionUp to 65% of a dose is excreted in the urine in 96 h. The major urinary metabolite appears to be diphenylmethoxyacetic acid in free or conjugated form; very little is excreted as unchanged drug. Diphenhydramine crosses the placenta and is excreted in breast milk.
- Urinary Excretion1.9
- Clerance6.2 ml/min/kg
- ToxicityThe estimated minimum lethal dose is 3 g. Toxic effects may be produced by plasma concentrations greater than 1 mg/L.
- LD50 (rat)LD50=500 mg/kg
- LD50 (mouse)N/A