Maybe carbonic anhyrdase inhibition, maybe lowering serotonin
Serotonin antagonists as treatment for COVID-19 / SARS – To Extract Knowledge from Matter
, and also maybe other interesting properties.
Famotidine, an Antiulcer Agent, Strongly Inhibits Helicobacter pylori and Human Carbonic Anhydrases. - PubMed - NCBI
"The high resolution X-ray structures of famotidine bound to hCA I and II revealed interesting aspects related to its CA inhibition mechanism, offering the possibility to develop antibacterials with a novel mechanism of action."
Here is @nullredvector 's thread/reference
Famotidine Has Antibiotic Actions, Esp Against E. Coli
Famotidine complexes with cobalt, maybe it complexes with other minerals ?
Famotidine, an Antiulcer Agent, Strongly Inhibits Helicobacter pylori and Human Carbonic Anhydrases. - PubMed - NCBI
"Antibacterial and antifungal activity of famotidine and its newly synthesized complex against representative bacteria: Escherichia coli, Staphilococcus aureus and Micrococcus lysodeikticus and fungi: Aspergillus niger and Candida albicans were examined. The results indicate a higher selectivity of the famotidine-Co(III) complex, as well as better growth inhibitory activity (lower MIC values (MIC, minimal inhibitory concentration)) in comparison with the drug alone."
Maybe famotidine keeps antiviral compounds from being excreted too quickly by its renal action
Effect of famotidine on ciprofloxacin pharmacokinetics after single intravenous and oral doses in rats. - PubMed - NCBI,
"These results suggest a possible reduction in the total clearance of ciprofloxacin, owing to inhibition of its renal tubular excretion by famotidine."
Maybe famotidine also is liver protective, adding to anti-shock properties in severe COVID events:
Hepatoprotective, antinociceptive and antioxidant activities of cimetidine, ranitidine and famotidine as histamine H2 receptor antagonists. - PubMed - NCBI
"...antioxidant activities of H(2) blockers have an analgesic activity and protective effect on CCl(4)-induced hepatotoxicity in mice."
Thanks. I just remembered that I had a thread on CA. The combination of anti-serotonin and CA inhibition is a rather rare property. Don't know of any other drug that has it. Let's hope famotidine production rights do not get bought out by Mr. Shkreli (or one of his non-incarcerated associates) and then get re-introduced at the low price of $999 for a box of 20 pills...
Famotidine Inhibits Carbonic Anhydrase (CA)