Updated: Aug 21
One day your medication is 'working' and then the next you don't feel like it's doing anything at all. Or perhaps it has stopped 'working' all together or you never really felt it 'worked' at all. Sound familiar? In this post we look at how your diet could be impacting the effectiveness of dexamphetamine (dex).
Is your diet particularly acidic? Acidic foods (including vitamin C supplements) decrease the absorption of dex, reducing its effect. Acidic foods also tend to make urine more acidic too, which increases the rate dex is released from the body, again decreasing the effectiveness. Normally around 30% of all dex you take is excreted in the urine. However highly acidic urine (around pH 4-5) will result in as much as 75% of the dex being eliminated from the body! That would make a huge difference to the effectiveness of dex. Whereas a low acid or alkaline urine (around pH 8) will result in less than 5% of dex being eliminated via your urine.
Antacids like Rennies or Tumms help alkaline stomach acid, so too does simple bicarbonate soda - because even on an empty stomach the absorption of dex can be reduced. Just thinking about food produces gastric acid which has a very low pH.
Dexamphetamine is a finicky medication, it is more effective when you are hydrated so drink plenty of water (not soft drinks, fruit juice or caffeine drinks as these are all highly acidic - sorry guys so too is chocolate) and do not take it with food. The general timeframe is to take dex at least 45min before food and no sooner than 2 hours after food. It is also best to avoid alcohol.
You will find many different Acidic/Alkaline food lists online to help you choose better food options and if you want to check the pH level of your urine you can pick up pH test strips from your chemist rather cheaply. Always speak to your doctor first about how you can get the best out of your medication and ALWAYS remember to tell all of your treating doctors what medication you are already taking (don't assume they know). Dex interacts with various vitamins/minerals and medications - including some very common antidepressants so if your doctor doesn't offer information don't be afraid to ask.
From the Dexamphetamine Product Information: Acidifying Agents: Gastrointestinal acidifying agents (guanethidine, reserpine, glutamic acid hydrochloride, ascorbic acid, fruit juices etc) lower absorption of amfetamines. Urinary acidifying agents (ammonium chloride, sodium acid phosphate etc) increase the concentration of the ionised species of the amfetamine molecule, thereby increasing urinary excretion. Both groups of agents lower blood levels and the efficacy of amfetamines. Alkalising Agents: Gastrointestinal alkalising agents (sodium bicarbonate etc) increase absorption of amfetamines. Urinary alkalising agents (acetazolamide and some thiazides) increase the concentration of the non-ionised species of the amfetamine molecule thereby decreasing urinary excretion. Click here for more information about interactions with other medications from the TGA's Dexamphetamine product information.
For more technical reading on drug metabolism: Urinary excretion of d-amphetamine following oral doses in humans: implications for urine drug testing
Duration of Detectable Methamphetamine and Amphetamine Excretion in Urine after Controlled Oral Administration of Methamphetamine to Humans *first published in 2013 on Hypersomnolence Australia's original website