Как то так?
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import pandas as pd
df = pd.read_csv('data - data.csv')
del df['Unnamed: 0']
df['Combined_Meds'] = df.astype(str).values.sum(axis=1)
df['Combined_Meds'] = df['Combined_Meds'].str.replace('nan', '', regex=False)
cols = list(df.columns)
cols = [cols[-1]] + cols[:-1]
df = df[cols]
df.sample(10)