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Abstract

The pharmacokinetics of diphenhydramine (DPHM) was compared in camels (n = 8) and horses (n = 6) following intravenous (i.v.) administration of a dose of 0.625 mg/kg body weight. In addition, the metabolism and urinary detection time of DPHM was evaluated in camels. The data obtained (median and range in brackets) in camels and horses, respectively, were as follows. The terminal elimination half lives (h) were 1.58 (1.13-2.58) and 6.11 (4.80-14.1), and the total body clearances (L/h per kg) were 1.42 (1.13-1.74) and 0.79 (0.66-0.90). The volumes of distribution at steady state (L/kg) were 2.38 (1.58-4.43) and 5.98 (4.60-8.31) and the volumes of the central compartment of the two compartment pharmacokinetic model were 1.58 (0.80-2.54) and 2.48 (1.79-3.17). All the pharmacokinetic parameters in camels were significantly different from those of horses. Five metabolites of DPHM were tentatively identified in the camel's urine. Two metabolites, diphenylmethoxyacetic acid and 1-(4-hydroxyphenyl)-phenylmethoxyacetic acid, were present in the acid fraction. Two metabolites, desamino-DPHM and diphenylmethanol, were identified in the basic fraction, in addition to DPHM itself, which was present mainly as a conjugate. Even after enzymatic hydrolysis, DPHM could be detected for up to 24 h in camels after an i.v. dose of 0.625 mg/kg body weight.

Development and validation of a liquid chromatography/tandem mass spectrometry assay for the simultaneous determination of d-amphetamine and diphenhydramine in beagle dog plasma and its application to a pharmacokinetic study

“…The maximum plasma con- Table 6. Studies on the pharmacokinetics of diphenhydramine have been reported in rabbits [9], sheep [20], human beings [19], camels and horses [33], except beagle dogs. There is only one literature on the pharmacokinetics of amphetamine in beagle dogs, reported by March et al [11], and the pharmacokinetic parameters after an oral administration of 10 mg of 'immediate- 11.6 ± 3.9 6.5 ± 0.8 AUC 0− (g h/mL) 3.8 ± 1.6 9.2 ± 3.1 AUC 0−∞ (g h/mL) 4.1 ± 2.1 9.5 ± 3.2 release' amphetamine dose are as follows: C max = 86.6 ng/mL, T max = 1 h, AUC 0− = 0.56 g h/mL, AUC 0−∞ = 0.67 g h/mL.…”

Pharmacokinetics of diphenhydramine following single‐dose intravenous and oral administration in non‐fasted adult horses

“…Pharmacokinetics of intravenously administered diphenhydramine have been previously reported in horses (Wasfi et al, 2003). When pharmacokinetic parameters are normalized for dose, most results are not similar between our study and the one by Wasfi et al Several differences exist to the current study including a higher dose administered in the current study (0.625 versus 1.0 mg/kg BW), method of analysis (gas chromatography-mass spectrometry versus liquid chromatography-tandem mass spectrometry), pharmacokinetic compartmental model utilized, and duration of sampling after administration (12 vs. 48 h).…”

“…diphenhydramine, and cetirizine, knowledge of their pharmacokinetics and pharmacodynamics is gradually being elucidated (Knych et al, 2016(Knych et al, , 2019Olsén et al, 2007Olsén et al, , 2008Olsén et al, , 2011. Pharmacokinetics of intravenously administered diphenhydramine have been evaluated in adult horses in one study (Wasfi et al, 2003); however, this is not a feasible route of administration for long-term use or by laypersons. In the study by Wasfi et al,a 0.625 mg/kg dose was utilized, whereas a maximum intravenous (IV) dose of 1 mg/kg has been reported for horses.…”

Preliminary Investigation of Bovine Whole Blood Xenotransfusion as a Therapeutic Modality for the Treatment of Anemia in Goats

“…In small animal medicine, the antihistamine diphenhydramine is the drug commonly used to prevent acute febrile and allergic transfusion reactions (25). Currently, there are no pharmacokinetic studies describing diphenhydramine in goats, although there are references among ruminant species for sheep (26) and camels (27). Future work should consider evaluating the effect of an antihistamine on reactions from xenotransfusion in goats (28).…”