In our latest question and answer, the pharmacist discusses whether or not Truvada is negatively affected by being on a keto diet.
I am on a ketogenic diet and have had an unplanned risky sex exposure - I may need Truvada or the PEP protocol. Can being a month in on keto diet result in serious illness if I take PEP? I am thinking of people talking about liver stuff, acidosis, kidneys - and can’t find any info. If it is problematic, how long would it take to shift my diet back to carbohydrate burning?
There isn't much data to go on regarding whether or not being on a ketogenic diet (i.e. no/low carbs) negatively affects prescription medication...and this is certainly the case for Truvada (emtricitabine; tenofovir disoproxil fumarate).
The theory is that since keto diets cause an increase in ketone bodies (which are used as an efficient fuel for the brain in the absence of carbohydrates), there may be an improvement in cognitive performance in those suffering from cognitive decline due to certain disease states (e.g. Alzheimer's disease, HIV, etc...).
One study, published in the Journal of Psychiatry and Behavioral Sciences, concluded:
Thus, it is conceivable that the ketogenic diet represents a novel, low-risk intervention capable of reducing cognitive impairment prevalence and severity in a rapidly aging HIV population.
Getting back to a keto diet and its potential effect on Truvada., as stated, there are no studies that have evaluated this.
Nevertheless, in this next section, I explore some of the known effects of this diet and whether or not there could be a cause for concern.
There are few things to take into account when considering how a keto diet could affect drug therapy, including:
Let's take a look at each of these separately.
It isn't thought that a keto diet will significantly increase or decrease the concentration of most drugs.
I say 'most' drugs since some studies have reported that certain ones can be affected.
One such drug is Depakote (valproic acid).
A study published in the Journal of Clinical Pharmacy and Therapeutics tested the effects of a keto diet on the drug concentrations of several antiepileptics:
The study found that blood concentration of all the above drugs decreased, with the exception of phenobarbital, which increased slightly.
All of the changes, however, were deemed to be not statistically significant, except for valproic acid. The serum concentration of the drug decreased from 67.07 μg/mL to 51.00 μg/mL. The study concluded:
Most anti-epileptic drug serum concentrations remained stable during the KD and other related dietary therapies except those of valproic acid. Therefore, serum concentrations of valproic acid should be monitored when the KD and other dietary therapies are concomitantly administered.
The data collected in this study is certainly interesting and hopefully, will lead to more with other classes of drugs.
It is likely though, that the effect that a keto diet has valproic acid concentrations won't apply to many others.
This is because valproic acid is technically a fatty acid, derived from the naturally occurring fatty acid valeric acid. Fatty acids are exactly what our bodies utilize for energy in the absence of carbohydrates..so in a sense, in a ketogenic state, our bodies metabolize valproic acid for energy.
This, of course, will significantly decrease concentrations of the drug.
The vast majority of drugs are not fatty acids though, and therefore, shouldn't be significantly affected by being in a ketogenic state.
What is likely more concerning than whether or not a keto diet has an effect on drug concentration, is the chance of additive or increased risk of side effects.
For example, studies show that a keto diet has a range of potential physiologic effects, including:
If a drug you are taking if affected by total body water content (e.g. lithium), being on a keto diet could be concerning.
Similarly, Zonegran (zonisamide) and Topamax (topiramate) can cause the blood to be more acidic. Since a keto diet can do the same, there may be an increased risk of metabolic acidosis and kidney stones.
It is important to speak with your doctor about a keto diet if you are considering it. There could be a potential issue with your current health state, or drugs you are taking.
There haven't been any studies on the effects of a keto diet on Truvada.
Truvada contains two drugs (Emtricitabine; Tenofovir disoproxil fumarate), neither of which are fatty acids, so it shouldn't have the same problem as valproic acid does.
Something that may be of concern, however, is the fact that Truvada can negatively affect kidney function, although this is relatively uncommon.
The prescribing information for Truvada does recommend that individuals taking the drug that have a risk (or history) of kidney dysfunction should have their kidney function and related values (e.g. serum phosphorus, urine glucose, and urine protein) tested periodically.
Some sources recommend avoiding a keto diet if you have problems with your kidneys. The lack of carbs may not be the issue, but the fact that protein intake may increase can cause stress.
If you are taking Truvada, it would be wise to discuss whether or not a keto diet is safe for your current medical situation.
Regardless of whether or not you are on a keto diet, if your doctor recommends you take Truvada, or go on a PEP (post-exposure prophylaxis) protocol, the benefits of doing so most likely outweigh the risks. The potential kidney-related issues of Truvada discussed above generally only occur (if they do at all), with long-term therapy.
Just like Truvada, there isn't any data on how a keto diet could affect the drugs used in a PEP protocol. Based on the information we have available, it isn't likely to have a significant effect on them.
Nevertheless, if it is recommended to go back to eating carbs as part of your diet, your body adjusts quickly. In most cases, you'll be out of a ketogenic state with your first carb-based meal.