Ammonium chloride Amfetamines

When a dmg is in its unionised form it will more readily diffuse from the urine to the blood. In an acidic urine, acidic drugs will diffuse back into the blood from the urine. Acidic compounds such as nitrofurantoin are excreted faster when the urinary pH is alkaline. Amfetamine, imipramine and amitriptyline are excreted more rapidly in acidic urine. The control of urinary pH in studies of pharmacokinetics is thus vital. It is difficult, however, to find compounds to use by the oral route for deliberate adjustment of urinary pH. Sodium bicarbonate and ammonium chloride may be used but are unpalatable. Intravenous administration of acidifying salt solutions presents one approach, especially for the forced diuresis of basic dmgs in cases of poisoning. 

Conversely, the elimination of basic drugs such as amfetamine, antihistamines, morphine and tricyclic antidepressants can be increased by making tubular filtrate more acidic by administration of ammonium chloride. 

The urinary excretion of amfetamines is increased by urinary acidifiers (ammonium chloride) and reduced by urinary alkalinisers (sodium bicarbonate). 

A study in 6 healthy subjects given dexamfetamine 10 to 15 mg found that when the urine was made alkaline (pH of about 8) by giving sodium bicarbonate, only 3% of the original dose of amfetamine was excreted over a 16-hour period, eompared with 55% when the urine was made acidic (pH of about 5) by taking ammonium chloride. Similar results have been reported elsewhere for amfetamine, dexamfetamine and metamfe-tamine. A further study found that the effects of amfetamine were increased and prolonged in subjects with alkaline urine. Psychoses resulting from amfetamine retention in patients with alkaline mine has been described. ... 

A well established and well understood interaction but reports of problems in practice seem rare. The interaction has been exploited to increase the clearance of amfetamines in cases of overdose by acidifying the urine with ammonium chloride. Conversely it can represent an undesirable interaction if therapeutic doses of amfetamines are excreted too rapidly. Care is needed to ensure that amfetamine toxicity does not develop if the urine is made alkaline with sodium bicarbonate or another urinary alkaliniser, acetazolamide. 

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