Generally, any distilled alcoholic beverage of 170 US proof or higher is considered to be a neutral spirit.Most yeasts cannot reproduce when the concentration of alcohol is higher than about 18%, so that is the practical limit for the strength of fermented drinks such as wine, beer, and sake. However, some strains of yeast have been developed that can reproduce in solutions of up to 25% ABV. Serving measures
Shot sizes
Shot sizes vary significantly from country to country. In the United Kingdom, serving size in licensed premises is regulated under the Weights and Measures Act (1985). A single serving size of spirits (gin, whisky, rum, and vodka) are sold in 25 ml or 35 ml quantities or multiples thereof. Beer is typically served in pints (568 ml), but is also served in half-pints or third-pints. In Israel, a single serving size of spirits is about twice as much, 50 or 60 mL. The shape of a glass can have a significant effect on how much one pours. A Cornell University study of students and bartenders pouring showed both groups pour more into short, wide glasses than into tall, slender glasses. Aiming to pour one shot of alcohol (1.5 ounces or 44.3 ml), students on average poured 45.5 ml & 59.6 ml (30% more) respectively into the tall and short glasses. The bartenders scored similarly, on average pouring 20.5% more into the short glasses. More experienced bartenders were more accurate, pouring 10.3% less alcohol than less experienced bartenders.
Resistance
Drug resistance to didanosine does develop, though slower than to zidovudine (ZDV). The most common mutation observed in vivo is L74V in the viral pol gene, which confers cross-resistance to zalcitabine; other mutations observed include K65R and M184V . Mechanism of action
Didanosine (ddI) is a nucleoside analogue of adenosine. It differs from other nucleoside analogues, because it does not have any of the regular bases, instead it has hypoxanthine attached to the sugar ring. Within the cell, ddI is phosphorylated to the active metabolite of dideoxyadenosine triphosphate, ddATP, by cellular enzymes. Like other anti-HIV nucleoside analogs, it acts as a chain terminator by incorporation and inhibits viral reverse transcriptase by competing with natural dATP. Pharmacokinetics
Oral absorption of didanosine is fairly low (42%) but rapid. Food substantially reduces didanosine bioavailability, and the drug should be administered on an empty stomach. The half-life in plasma is only 1.5 hours, but in the intracellular environment more than 12 hours. An enteric-coated formulation is now marketed as well. Elimination is predominantly renal; the kidneys actively secrete didanosine, the amount being 20% of the oral dose. History
The related pro-drug of didanosine, 2′,3′-dideoxyadenosine (ddA), was initially synthesized by Morris J. Robins (professor of Organic Chemistry at Brigham Young University) and R.K. Robins in 1964. Subsequently, Samuel Broder, Hiroaki Mitsuya, and Robert Yarchoan in the National Cancer Institute (NCI) found that ddA and ddI could inhibit HIV replication in the test tube and conducted initial clinical trials showing that didanosine had activity in patients infected with HIV.