Sydepres Drug Interactions

The possibility should be borne in mind that phenothiazines may: Increase the central nervous system depression produced by drugs eg, alcohol, hypnotics, sedatives or strong analgesics; antagonize the action of adrenaline and other sympathomimetic agents and reverse the blood-pressure lowering effects of adrenergic-blocking agents eg, guanethidine and clonidine; impair the antiparkinsonian effect of L-dopa, the effect of anticonvulsants, metabolism of tricyclic antidepressants and the control of diabetes; increase the effect of anticoagulants; interact with lithium.
Anti-parkinsonian drugs may enhance anticholinergic effects.
Phenothiazine may enhance the cardiac depressant effects of quinidine, the absorption of corticosteroids and digoxin and neuromuscular blocking agents.
ACE Inhibitors, hypotension-producing medications, other (concurrent use with phenothiazines may produce severe hypotension with postural syncope).
Beta-adrenergic blocking agents: Concurrent use of beta-blockers, possibly including ophthalmic, with phenothiazines may result in an increased plasma concentration of each medication because of inhibition of metabolism; this may result in additive hypotensive effects, irreversible retinopathy, cardiac arrhythmias, and tardive dyskinesia.
Anticholinergics or other medications with anticholinergic action: Concurrent use with phenothiazine may intensify anticholinergic side effects, especially confusion, hallucinations, and nightmares, because of the phenothiazines secondary anticholinergic effects; medications with anticholinergic effects may potentiate the hyperpyretic effect of phenothiazines, especially when environmental temperatures are high, by preventing sweating as cooling mechanism; this effect could lead to heat stroke; also, patients should be advised to report occurrence of gastrointestinal problems since paralytic ileus may occur with concurrent therapy.
Antacids, aluminum- or magnesium-containing or Antidiarrheal, absorbent: Concurrent use of these medications with phenothiazines may inhibit the absorption of orally administered phenothiazines; simultaneous use should be avoided.
Amphetamines: Stimulants effects may be decreased when amphetamines are used concurrently with phenothiazine since phenothiazines produce alpha-adrenergic blockade; also, the antipsychotic effectiveness of phenothiazines may be reduced.