Trimethobenzamide (trade names Tebamide, Tigan) is an antiemetic used to prevent nausea and vomiting. Trimethobenzamide is an antagonist of the D2 receptor, that affects the chemoreceptor trigger zone (CTZ) of the medulla oblongata to suppress nausea and vomiting. The oral bioavailability of trimethobenzamide is 60% to 100%. The time to peak is about 45 minutes after oral administration and; I.M. about 30 minutes after intramuscular administration. The onset action of trimethobenzamide for antiemetic effects is 10-40 minutes after oral administration and; 15-35 minutes after intramuscular administration. The duration of action is 3-4 hours. Trimethobenzamide is generally considered the most potent antiemetic that does not have effects on the serotonergic, dopaminergic, or histaminergic systems, so it has a lower likelihood of causing undesired side effects. Possible side effects include drowsiness, dizziness, headache, diarrhea, muscle cramps, and blurred vision. More serious adverse effects include skin rash, tremors, parkinsonism, and jaundice.

Diphenidol, a nonphenothiazinic antiemetic agent used primarily in patients with Meniere disease and labyrinthopathies to treat vomiting and vertigo, is considered to be a relatively safe drug. Since it was first approved in the United States in 1967, this drug has been widely used in Latin America and Asia and has contributed to sporadic suicidal and accidental poisonings in mainland China and Taiwan. The mechanism by which diphenidol exerts its antiemetic and antivertigo effects is not precisely known. It is thought to diminish vestibular stimulation and depress labyrinthine function and as an antimuscarinic agent. An action on the medullary chemoreceptive trigger zone may also be involved in the antiemetic effect. Diphenidol has no significant sedative, tranquilizing, or antihistaminic action. It has a weak peripheral anticholinergic effect. Diphenidol is used to relieve or prevent nausea, vomiting, and dizziness caused by certain medical problems.

Meclizine, a piperazine-derivative H1-receptor antagonist similar to buclizine, cyclizine, and hydroxyzine, is used as an antivertigo/antiemetic agent. Meclizine is used in the management of nausea, vomiting, and dizziness associated with motion sickness and vertigo in diseases affecting the vestibular apparatus. Along with its actions as an antagonist at H1-receptors, meclizine also possesses anticholinergic, central nervous system depressant, and local anesthetic effects. Meclizine depresses labyrinth excitability and vestibular stimulation and may affect the medullary chemoreceptor trigger zone. It is sold under the brand names Bonine, Bonamine, Antivert, Postafen, Sea Legs, and Dramamine II.

Diphenidol, a nonphenothiazinic antiemetic agent used primarily in patients with Meniere disease and labyrinthopathies to treat vomiting and vertigo, is considered to be a relatively safe drug. Since it was first approved in the United States in 1967, this drug has been widely used in Latin America and Asia and has contributed to sporadic suicidal and accidental poisonings in mainland China and Taiwan. The mechanism by which diphenidol exerts its antiemetic and antivertigo effects is not precisely known. It is thought to diminish vestibular stimulation and depress labyrinthine function and as an antimuscarinic agent. An action on the medullary chemoreceptive trigger zone may also be involved in the antiemetic effect. Diphenidol has no significant sedative, tranquilizing, or antihistaminic action. It has a weak peripheral anticholinergic effect. Diphenidol is used to relieve or prevent nausea, vomiting, and dizziness caused by certain medical problems.