Other examples include terfenadine (Seldane, Seldane-D), astemizole (Hismanal), cisapride (Propulsid, withdrawn in many countries for prolonging the QT time) and pimozide (Orap). Theophylline, which is used mostly in asthma, is also contraindicated. Erythromycin and doxycycline can have a synergistic effect when combined and kill bacteria (E. coli) with a higher potency than the sum of the two drugs together. This synergistic relationship is only temporary. After approximately 72 hours, the relationship shifts to become antagonistic, whereby a 50/50 combination of the two drugs kills less bacteria than if the two drugs were administered separately.It may alter the effectiveness of combined oral contraceptive pills because of its effect on the gut flora. A review found that when erythromycin was given with certain oral contraceptives, there was an increase in the maximum serum concentrations and AUC of estradiol and dienogest.Erythromycin is an inhibitor of the cytochrome P450 system, which means it can have a rapid effect on levels of other drugs metabolised by this system, e.g., warfarin. Pharmacology
Mechanism of action
Erythromycin displays bacteriostatic activity or inhibits growth of bacteria, especially at higher concentrations. By binding to the 50s subunit of the bacterial  rRNA complex, protein synthesis and subsequent structure and function processes critical for life or replication are inhibited. Erythromycin interferes with aminoacyl translocation, preventing the transfer of the tRNA bound at the A site of the rRNA complex to the P site of the rRNA complex.
PDGFβ receptor) proteins that contribute to the development and/or progression of IMF.A mutation in one of the two NOTCH3 genes has been reported to occur in a single family with autosomal dominant inheritance of IMF: 9 of this familys members had IMF plus the mutation while 7 of its members did not have IMF or the mutation. Since the mutated NOTCH3 gene in this family produces an overactive neurogenic locus notch homolog protein 3 product that in cell culture studies increases the expression of the PDGFRB genes product, the PDGFβ receptor, this NOTCH3 mutation may promote the development and/or progression of IMF in a manner similar to PDGFRB mutant genes, i.e. by increasing the number and therefore overall activity of the PDGFβ receptor. Further studies are needed to define NOTCH3 gene mutations frequency of occurrence in, and contribution to the development of, IMF. Solitary IMF tumors
Solitary IMF tumors represent 50 to 74% of all IMF cases. These tumors commonly present with a mass that infiltrates the surrounding tissue in the head and neck areas (e.g. in the ethmoid sinus/maxillary sinus, infratemporal fossa, tongue, hard palate, behind an ear, or temporal bone); less commonly in other sites such as the scapula/axilla area, lower back, or soft tissue/bone in the lower leg; and also less commonly in visceral organs such as the pancreas, spleen, lung, or heart. Solitary IMF tumors often (i.e. 25 to 61% of cases in different studies) regress spontaneously.