Phenothiazines, contraindications

Stemetil is a proprietary preparation of prochlorperazine, a phenothiazine used in vertigo and labyrinthine disorders. Stemetil is available as tablets, syrup and injection. There is no contraindication to the concurrent use of paracetamol and prochlorperazine. 

Phenothiazines tend to have antimuscarinic properties and are therefore contraindicated for use in patients with closed-angle glaucoma. Antimuscarinics are contraindicated in closed-angle glaucoma as they may worsen the condition. 

Contraindications Coma, myelosuppression, hypersensitivity to other piperazine phenothiazines, severe cardiovascular disease, severe CNS depression, subcortical brain damage... 

Contraindications Angle-closure glaucoma, GI orGU obstruction, hypersensitivity to phenothiazines, severe CNS depression or coma... 

Phenothiazines and other psychotropic agents (e.g. prochlorperazine and haloperidol) are contraindicated because they cause extrapyramidal symptoms despite being potentially efficacious. 

Bromocriptine is also available as an oral formulation, but oral administration to horses has not been reported. This drug should not be used in pregnant or lactating animals because of its effects on prolactin and lactation. Concomitant administration of bromocriptine and the phenothiazine tranquilizers or reserpine is contraindicated. 

The hemodynamic effects of the phenothiazines can be significant. Acepromazine is associated with decreased systolic, mean and diastolic blood pressures (Marroum et al 1994). The heart rate is usually unchanged after acepromazine administration. The fall in blood pressure is a result of decreased total peripheral resistance caused by antagonism of adrenoceptors in the vasculature. Despite a fall in blood pressure, administration of acepromazine (0.05 mg/kg) can be associated with improved cardiac output, as stroke volume increases with the decrease in peripheral resistance (Steffey et al 1985). This would not be the case in a horse that is volume depleted as a result of colic or blood loss and acepromazine is contraindicated in these cases because of the potential for the development of extreme hypotension and cardiovascular collapse. There can be significant individual variability in the degree of hypotension that results from the... 

Phenothiazines may decrease the seizure threshold in small animal patients and are contraindicated in dogs and cats with seizure disorders. Although in the horse, seizure disorders are rare (see Ch. 9) and the influence of these drugs on the seizure threshold is unknown, the phenothiazines should be avoided in horses with a history of seizures. Phenothiazines are also contraindicated in animals recently exposed to organophosphate insecticides because of the potential to enhance the toxicity to these drugs (Fernandez et al 1975). In addition, the concomitant administration of phenothiazines and procaine or procaine benzylpenicillin is not advised because of the potential to enhance the adverse effects of procaine (Chapman et al 1992). 

Adults After cyanosis is overcome, atropine sulfate should be used, 2 mg i.v. Doses should be repeated at 5-10 min intervals until signs of atropin-ization appear. This should be maintained for 24 h or longer if necessary. 2-PAM (pralidoxime chloride) should be given. Adult dose 1 g, slowly, intravenously. Contraindicated are morphine, aminophylline, theophylline, phenothiazine tranquilizers, and barbiturates. 

Phenothiazine derivatives potentiate the acute toxicity of OPs (Arter-berry et al. 1962). Individuals treated with phenothiazine derivatives should avoid occupations with high exposure risk to insecticides. Phenothiazines appear contraindicated in treating insecticide-related delirium. 

Dopamine-receptor antagonists having antipsychotic properties, such as phenothiazine, butyrophenone, and thioxanthene derivatives, and Gl-stimulant drugs, such as metoclopramide, are contraindicated with pergolide. The... 

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