Methadone Ammonium chloride

Methadone Hydrochloride Visual incompatibilities of methadone hydrochloride were observed with solutions of aminophylline, ammonium chloride, amylo-barbitone sodium, chlorothiazide sodium, heparin sodium, nitrofurantoin sodium, novobiocin, pentobarbitone sodium, phenobarbitone sodium, phenytoin sodium, quinalbarbitone sodium, sodium bicarbonate, sodium iodide, sulfadiazine sodium, sulfafurazole diethanolamine, or thiopentone sodium. 

Urinary methadone clearance is increased if the urine is made acid (e.g. by giving ammonium chloride) and reduced if it is made alkaline (e.g. by giving sodium bicarbonate). The urinary clearance of dextropropoxyphene (propoxyphene) and pethidine (meperidine) may also be increased by acidification of the urine. 

A pharmacokinetic study in 5 healthy subjects given a 10-mg intramuscular dose of methadone found that the plasma half-life was 19.5 hours when the urine was made acidic (pH 5.2) with ammonium chloride, compared with 42.1 hours when the urine was made alkaline (pH 7.8) with sodium bicarbonate. The clearance of the methadone fell from 134 to 91.9 mL/minute when the urine was changed from acidic to alkaline. ... 

The effect of urinary pH on the clearance of methadone is an established interaction, but of uncertain importance. Be alert for any evidence of reduced methadone effects in patients whose urine becomes acidic because they are taking large doses of ammonium chloride. Lowering the urinary pH to 5 with ammonium chloride to increase the clearance can also be used to treat toxicity. Theoretically, urinary alkalinisers such as sodium bicarbonate and acetazolamide may increase the effect of methadone. 

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