**3. Results**

#### *3.1. Clinical and Demographic and Characteristics of Patients*

Data were obtained from 112 CKD patients, 69 (61.6%) females and 43 (38.4%) males. The mean age of this study population was 77.1 ± 10.4 years: 11 patients (10.0%) were between 30 and 60 years, 8 (7.1%) were between 61 and 70 years, 44 (39.3%) were between 71 and 80 years, and 49 (43.7%) were older than 80 years (Table 1).


**Table 1.** Characteristics of the study population (n = 112).

The most common comorbid conditions (Table 1) were hypertension in 52 patients (46.4%), diabetes mellitus in 25 (22.3%), dyslipidemia in 33 (29.5%), anemia in 13 (11.6%), and hyperuricemia in 11 (9.8%).

#### *3.2. Prevalence and Pattern of Potential Drug–Drug Interactions*

A total number of 957 prescribed medications were identified. The minimum number of prescribed medications per patient was 1, the maximum was 17, and the mean number was

8.6 ± 3.4 medications. Only one patient was not taking any medication. The most commonly prescribed medications were omeprazole (30.6%), acetaminophen (30.6%), salicylic acid (26.1%), bisoprolol (25.2%), furosemide (22.5%), and allopurinol (21.6%).

Among 111 individuals 928 pDDIs were identified, and 67 (60.3%) patients showed 1–10 pDDIs, while 34 (30.6%) presented more than 10. Only 10 patients (9%) did not have any interaction (Table 2).


**Table 2.** Frequency of potential drug–drug interactions (pDDIs) per patient (n = 111 \*).

\* One patient had not taken any drugs.

According to the Lexicomp® severity classification, 11 (1.2%) pDDIs were Type A (no known interaction), 84 (9.1%) were Type B (mild severity), 717 (77.3%) were Type C (moderate severity), 106 (11.4%) were Type D (major severity), and 10 (1.1%) were Type X (avoid drug combination) (Table 3).

**Table 3.** Severity of potential drug–drug interactions (pDDIs; n = 928) among studied chronic kidney disease (CKD) patients.


Table 4 shows the most frequent pDDIs by severity group: levothyroxine + omeprazole with 9 cases in the Type B group (10.7%), acenocoumarol + omeprazole with 11 cases in Type C (1.5%), and acenocoumarol + allopurinol with 8 cases in Type D (7.5%).


**Table 4.** Most frequent potential drug–drug interactions (pDDIs) by severity group.

In addition, Type X (avoid drug combination) pDDIs were found in 10 CKD patients (Table 5).


**Table 5.** Potential drug–drug interactions Type X (avoid drug combination) found in the studied CKD patients.

It was also observed that some drugs were present in a large number of pDDIs such as hydrochlorothiazide (15%), acetylsalicylic acid (10%), or furosemide (9%). The most frequent drugs present in pDDIs in the study group are shown in Figure 1.

**Figure 1.** Frequency of main drugs with potential drug–drug interactions (n = 928).

#### *3.3. Factors Associated with Potential Drug–Drug Interactions on CKD Patients*

Age and concomitant drugs were significantly associated with the number of pDDIs (*p* < 0.05; Table 6). In contrast, demographic and clinical variables, such as gender, CKD stage, or the number of chronic comorbid diseases were not significantly associated with the number of pDDIs (Table 6).


**Table 6.** Potential drug–drug interactions (pDDIs) among 111 \* CKD patients according to demographic and clinical variables groups.

\* One patient had not taken any drugs; \*\* according to the classification of chronic kidney disease from Kidney Disease: Improving Global Outcomes (KDIGO); 1 ANOVA Kruskal–Wallis test; 2 Mann–Whitney *t*-test.
