Excipients medication interactions

A less wordy definition appears in the Oxford Concise Medical Reference Dictionary as . . . a substance that is combined with a drug to render it suitable for administration for example in the form of pills. Excipients should have no pharmacological actions themselves . There are, however, indications that in certain situations, excipients do interact with the drug... 

Selected food hypersensitivity and medication interaction mainly due to one or more excipients may also preclude use of certain medications as listed in Table 4.3. 

Transdermal delivery of certain APIs is now common for the treatment of some medical conditions, and there are several excipients that are promoted as transdermal penetration enhancers. One of the earlier materials developed was laurocapram (Azone ). There is a detrimental interaction between laurocapram and mineral oil (liquid paraffin) whereby when both are included in the same formulation, the skin penetration-enhancing properties of laurocapram are lost. Such interactions have implications for extemporaneous mixing of different cream and ointment formulations in the pharmacy. 

Water may be considered a diluent in liquid presentations as it provides the required dose in a volume that can be accurately dispensed or administered. It is also invariably present in medications for topical or transdermal application. Water can be one of the most problematic companion materials in a dosage form because of its capability to promote hydrolysis, act as a vehicle for other molecular interactions, or simply be a medium for microbial growth. Such properties illustrate how a material that resolves one problem may pose others that in turn require the presence of additional excipients. 

Product quality can be compromised during manufacture, transport, storage or use. The causes of deterioration can be manifold and product-specific. They include microbial spoilage or chemical transformation of the active or physical changes that alter performance in vivo. Deterioration can compromise safety or make the medication less attractive, which means it may not be used. Excipients can contribute to or cause such changes unless carefully screened for possible interactions in preformulation studies. 

Previous occurrence of cystitis more than twice in last 12 months High temperature (may be pyelonephritis) Pregnant or breast-feeding Hypersensitivity to trimethoprim or any excipients of the tablets Known renal impairment Known blood dyscrasias Children Men Non-sexually active women Interaction with current medication If patient refuses to give consent... 

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