tNeratinib (NER) and pelitinib (PEL) are irreversible tyrosine kinase inhibitors (TKIs) that have beenrecently employed in cancer treatment. Apigenin (API), among other flavonoids, is known to haveantioxidant, anti-proliferative, and carcinogenic effect. API can potentiate the antitumor effect ofchemotherapeutic agents and/or alleviate the side effects of many anticancer agents. Since TKIs aremostly metabolized by CYP3A4 enzymes and that API could alter the enzymatic activity, potential druginteractions could be expected following their co-aministration.

Background: Ombitasvir/paritaprevir/ritonavir/dasabuvir (Viekira Pak®) are the newest medicines approved for use in the treatment of hepatitis C virus (HCV) and are available in tablet form as an oral combination. Specifically, these agents are indicated in the treatment of HCV in patients with genotype 1 infection. Due to the therapeutic importance and increased use of Viekira Pak, proper methods for its determination in bulk and pharmaceutical formulations must be developed.

Tamoxifen (TAM) is a non-steroidal estrogen receptor antagonist that enhances erlotinib (ERL)-inducedcytotoxicity in the treatment of NSCLC. ERL and TAM are metabolized by CYP3A4 enzymes. In addition,both drugs have the potential of altering the enzymatic activity through either inhibition (ERL) or induc-tion (TAM). Thus it was expected that pharmacokinetics (PK) drug–drug interactions (DDIs) could beencountered following their co-administration.

A new rapid and simple stability-indicating spectrofluorimetric method has been developed for the determination of two irreversible tyrosine kinase inhibitors (TKIs), neratinib (NER) and pelitinib (PEL). The method is based upon measurement of the native fluorescence intensity of both drugs at λex 270 nm in aqueous borate buffer solutions (pH 10.5). The fluorescence intensity