Unlike the didanosine chewable/dispersible tablets, didanosine gastro-resistant capsules do not contain antacids and therefore drug interactions mediated by altered gastric pH are not anticipated when didanosine gastro-resistant capsules are co-administered with medicinal products where absorption is influenced by gastric acidity. Specific interaction studies with ketoconazole showed no evidence of significant interaction.
Videx Summary of Product Characteristics, Bristol-Myers Squibb Pharmaceuticals Ltd, April 2016.

Coadministration of didanosine EC (400 mg single dose) and ketoconazole (200 mg single dose) to 21 HIV-negative subjects resulted in no change in the AUC and Cmax of ketoconazole. When the buffered formulation of ddI (375 mg twice daily for 4 days) was coadministered with ketoconazole (200 mg once daily for 4 days, 2 h before ddI) to 12 HIV-infected subjects, there was no change in ddI AUC and a 12% decrease in Cmax.
Videx Prescribing Information, Bristol-Myers Squibb Company, December 2018.

The effect of the didanosine encapsulated enteric coated beadlet formulation (400 mg) on ketoconazole (200 mg) was evaluated in 21 healthy volunteers. The geometric mean Cmax and AUC values were similar (<3% difference) when given alone or in combination and 90% CI of the ratios of the geometric means fell within the criteria defined for a lack of interaction (0.75 to 1.33). Didanosine as this formulation did not affect the pharmacokinetics of ketoconazole and the drugs may be administered simultaneously.
Lack of effect of simultaneously administered didanosine encapsulated enteric bead formulation (Videx EC) on oral absorption of indinavir, ketoconazole and ciprofloxacin. Damle BD, et al. Antimicrob Agent Chemother, 2002, 46:385-391.

The steady state pharmacokinetics of didanosine (375 mg twice daily) and ketoconazole (200 mg daily) were evaluated when given alone or in combination (ketoconazole 2 h prior to didanosine) to 12 HIV-infected subjects. There was a statistically significant reduction (12%) in didanosine Cmax when given with ketoconazole (1836 ng/ml) than alone (2094 ng/ml). Didanosine AUC was reduced by 8% when given in combination (2872 ng.h/ml) than alone (3107 ng.h/ml). There were no significant differences in ketoconazole pharmacokinetics when give alone or with didanosine. Coadministration of didanosine and ketoconazole does not result in a clinically significant interaction and it is not necessary to alter the dosing regimen of either drug as alone as ketoconazole is administered 2 h before ddI.
Pharmacokinetics of didanosine and ketoconazole after coadministration to patients seropositive for the human immunodeficiency virus. Knupp CA, et al. J Clin Pharmacol, 1993, 33: 912-917.