Table 3

Description and frequency of selected Contraindicated, Avoid/use alternative (Medscape and Epocrates databases) and Avoid combination-X (Lexicomp database) potential drug–drug interations

Drug combinationDescriptionNumber (%) of patients
Medscape
contraindicated
1.Erythromycin- simvastatin
Serious – use alternative
1.Carbamazepine-diazepam
2.Carbamazepine-clozapine

  1. Erythromycin- diazepam

  2. Azithromycin-dalteparin

Erythromycin base will increase the level or effect of simvastatin by affecting hepatic/intestinal enzyme CYP3A4 metabolism
Carbamazepine will decrease the level or effect of diazepam by affecting hepatic/intestinal enzyme CYP3A4 metabolism
Carbamazepine will decrease the level or effect of clozapine by affecting hepatic/intestinal enzyme CYP3A4 metabolism
Erythromycin base will increase the level or effect of diazepam by affecting hepatic/intestinal enzyme CYP3A4 metabolism
Azithromycin increases effects of dalteparin by decreasing metabolism		1 (0.03%)
19 (0.63%)
17 (0.56%)
7 (0.23%)
3 (0.1%)
Epocrates contraindicated

  1. Olanzapine-potassium chloride

  2. Haloperidol-potassium chloride


3.Clozapine-potassium chloride

  1. Lorazepam - metoclopramide

  2. Midazolam- metoclopramide

Contraindicated for solid potassium dose forms; use alternative dose forms: combination may delay solid potassium passage through gastrointestinal (GI) tract, increasing risk of ulcerative/stenotic lesions (anticholinergics slow GI transit, increasing local exposure to high potassium concentration)
Contraindicated if seizure disorder use; otherwise, use alternative or monitor respiratory rate; combination may alter seizure control; may increase risk of profound central nervous system (CNS) and respiratory depression, psychomotor impairment		8 (0.19%)
6 (0.14%)
4 (0.10%)
3 (0.07%)
3 (0.07%)
Lexicomp
Avoid combination
1.Diazepam-olanzapine
2.Midazolam-olanzapine
3.Lorazepam-olanzapine
4.Bromazepam-olanzapine
5.Clozapine-olanzapine		Avoid concomitant use of parenteral benzodiazepines and intramuscular (IM) olanzapine due to risks of additive adverse effects (eg,cardiorespiratory depression, excessive sedation). Additive pharmacologic effects might also be expected with oral use of these agents, but specific recommendations for management are lacking
Consider alternatives to this combination whenever possible. If combined, monitor closely for signs and symptoms of gastrointestinal hypomotility (eg, constipation, nausea, abdominal distension or pain, vomiting) and consider prophylactic laxative treatment		48 (9.39%)
36 (7.04%)
32 (6.26%)
27 (5.28%)
25 (4.89%)