Table 4 Level of pDDIs and potential adverse outcome with respective combined prescribed medications (N = 224)

Fluoxetine -Amitriptyline

10(4.5)

Serious

Fluoxetine increases the effect of amitriptyline by affecting CYP2C19.

Fluoxetine and amitriptyline both increase serotonin levels. Avoid use in combination.

Carbamazepine-diazepam

8(3.6)

Serious

Carbamazepine will decrease the level or effect of diazepam by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug.

Carbamazepine-haloperidol

7(3.1)

Serious

Carbamazepine will decrease the level or effect of haloperidol by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug.

Fluoxetine-Risperidone

6(2.7)

Serious

Fluoxetine will increase the level or effect of risperidone by affecting hepatic enzyme CYP2D6 metabolism. Avoid or Use Alternate Drug.

Fluoxetine-Haloperidol

5(2.2)

Serious

Fluoxetine will increase the level or effect of haloperidol by affecting hepatic enzyme CYP2D6 metabolism. Avoid or Use Alternate Drug.

Chlorpromazine-Amitriptyline

5(2.2)

Serious

Chlorpromazine and amitriptyline both increase QTc interval. Avoid or Use Alternate Drug.

Chlorpromazine-Haloperidol

4(1.8)

Serious

chlorpromazine and haloperidol both increase QTc interval. Avoid or Use Alternate Drug.

Fluoxetine-cimetidine

4(1.8)

Serious

Fluoxetine will increase the level or effect of cimetidine by affecting hepatic enzyme CYP2C19 metabolism. Avoid or Use Alternate Drug.

Fluphenazine deaconate-haloperidol

3(1.3)

Serious

fluphenazine and haloperidol both increase QTc interval. Avoid or Use Alternate Drug.

Chlorpromazine-Trihexyphenidyl

45(20.1)

Significant

Chlorpromazine increases effects of trihexyphenidyl by pharmacodynamic synergism. Use Caution/Monitor. Potential for additive anticholinergic effects.

Haloperidol-Trihexyphenidyl

32(14.3)

Significant

haloperidol increases effects of trihexyphenidyl by pharmacodynamic synergism. Use Caution/Monitor. Potential for additive anticholinergic effects.

Trifluoperazine-trihexyphenidyl

25(11.2)

Significant

trifluoperazine increases effects of trihexyphenidyl by pharmacodynamic synergism. Use Caution/Monitor. Potential for additive anticholinergic effects.

Fluphenazine decanoate-trihexyphenidyl

22(9.8)

Significant

Fluphenazine increases effects of trihexyphenidyl by pharmacodynamic synergism. Use Caution/Monitor. Potential for additive anticholinergic effects.

Fluoxetine- Amitriptyline

10(4.5)

Amitriptyline and fluoxetine both increase QTc interval. Modify Therapy/Monitor Closely.

Carbamazepine-diazepam

8(3.6)

Significant

Carbamazepine decreases levels of diazepam by increasing metabolism. Use Caution/Monitor.

Carbamazepine-haloperidol

7 (3.6)

Significant

Carbamazepine decreases levels of haloperidol by increasing metabolism. Use Caution/Monitor.

Fluoxetine-Risperidone

6(2.7)

Significant

Fluoxetine and risperidone both increase QTc interval. Use Caution/Monitor.

Fluoxetine-Haloperidol

5(2.2)

Significant

Fluoxetine and haloperidol both increase QTc interval. Modify Therapy/Monitor Closely.

Chlorpromazine-Amitriptyline

5(2.2)

Significant

Chlorpromazine and amitriptyline both increase sedation. Use Caution/Monitor.

Chlorpromazine-Haloperidol

4(1.8)

Significant

-Chlorpromazine and haloperidol both increase sedation. Use Caution/Monitor.

-chlorpromazine and haloperidol both increase antidopaminergic effects, including extrapyramidal symptoms and neuroleptic malignant syndrome. Use Caution/Monitor.

Fluphenazine-haloperidol

3(1.3))

Significant

Fluphenazine and haloperidol both increase sedation. Use Caution/Monitor.

-Fluphenazine and haloperidol both increase antidopaminergic effects, including extrapyramidal symptoms and neuroleptic malignant syndrome. Use Caution/Monitor.