STEP 6C. Examine any medications, recreational drugs or alcohol for potential testosterone-lowering qualities.
Yes, almost all recreational drugs (and alcohol) can lower testosterone, which is something I cover in the following links:
Painkillers lower testosterone as well. Of course, there are legitimate uses for painkillers, but there are also tons of men addicted to them as well and hammering their hormones while they are at it.
Intuitively, I think that many men realize that these supposed "feel good" drugs are hard on our hormones, so the above is probably no surprise. However, what I often find on The Peak Testosterone Forum, is that many guys do not realize that legitimate, FDA-approved pharmaceuticals can also significantly lower testosterone as well. Why in the world would the FDA approve a drug that lowered testosterone without a warning label, right? Well, it just doesn't work that way. There a MANY drugs out there that lower testosterone and, making matters worse, most doctors do not know about it.
In modern, urbanized societies, it is very common for men over 40 to be on more than one medication and, of course, this just increase one's odds even more. Here are the 13 Major Classes of Drugs that can Decrease Baseline Testosterone Levels (and there are undoubtedly more):
CAUTION: Do NOT discontinue any medication without discussing it first with your doctor. In many cases, dosage can be reduced or an alternative medication found, but this should be discussed with your physician first.
1. Antipsychotics. These are especially hard on testosterone through a variety of pathways but are notorious for raising prolactin levels. Of course, prolactin fights testosterone and libido and if it goes too high will lead to sexual dysfunction in many ways. For more information, see my link on Testosterone and the Antipsychotics.
2. Opiate Paikillers (Percocet, Vicodin, Morphine, etc.). These all will tend to lower testosterone via inhibition of LH (leutinizing hormone), the molecule released by the pituitary to signal the testes to increase testosterone production. One review noted that "a large majority of men consuming sustained-action opioids have symptomatic androgen deficiency which apparently responds to replacement therapy. Opioid-induced androgen deficiency is frequently overlooked." 
3. Antifungal (Clotrimazole, Nizoral and Ketoconazole). Even something as simple as trying to get rid of a fungal infection can lower testosterone levels appreciably.  We have had a number of complaints on our forum about clortrimazole, especially when applied directly to the scrotum or penis. Look at what these posters wrote:
"The doctors claimed that I would not need to get circumcised and that I could use this cream as long as I needed to. I was never warned about any possible side-effects. At about the one year mark of daily clotrimazole use, I began applying the clotrimazole cream to my scrotum and the surrounding areas as I began to get jock itch. About a year and 8 months into this, I began to lose lean weight for unknown reasons. I noticed that I had lost about 24 lbs of lean weight with basically zero change in diet or exercise routine (or lack thereof). I also noticed that my strength had also decreased quite a bit. Doors that were once light became heavy and my 112 lb girlfriend seemed to be harder to pickup. I chalked all of this up to stress from a new job and aging (I was 26 at the time - too young for any of this stuff to start happening). I asked doctors what was happening and they had no answers...At about the 2.4 years mark, I started doing research on the relationship between testosterone and clotrimazole. The first journal article I found indicated that clotrimazole is a potent inhibitor of the P450 cytochrome enzyme. P450, as I'm sure you all know, is an enzyme directly involved in testosterone metabolism." 
"I just wanted to post saying the same thing about clotrimazole cream. I used it for only a few weeks back in July last year for jock itch, but it was applied near the scrotum. After using the cream for a few weeks I noticed my scrotum had shrunk in size! My testicles don't hang low anymore (about half as low as they used to), even in a hot shower they just do not hang low anymore, even 7/8 months later! For me I have no doubt it was caused by the cream, it was such an obvious change after 2 weeks of use! :( but fortunately I didn't get any other side effects. Its a shame the anti androgenic side effects are so potent because it did clear up the fungal infection a treat. I've had some sort of weird non itchy fungal infection on the head of my penis for years now, but I'm scared to treat it with anymore antifungal creams because the clotrimazole cream permanently shrunk my scrotum! I wish I never used the stuff!" 
I don't see a lot of reports like this out on the web, but there is some scary research on the subject. Check this out the title of this journal article: "Clotrimazole is a selective and potent inhibitor of rat cytochrome P450 3A subfamily-related testosterone metabolism." 
4. Arrythmias (Amiodarone). This drug for heart arrthymia has high iodine content and can interfere with thyroid function, which, in turn, could lower testosterone. 
5. Lithium. Of course, lithium can be a life saver for someone with bipolar disorder.  However, this can interfere with the thyroid and lead to hypothyroisim, which in turn can interfere with testosterone production. 
6. Diabetic (Sulfonylurea). These drugs sometimes used to treat type II diabetes can result in hypothyroidism and, therefore, potentially, a drop in testosterone. 
7. Oxycodone (Oxycontin). This pain medication tends to raise prolactin and in some men may lower testosterone.  It also can have a side effect of very significantly lowering testosterone in some sensitive men as well.
8. Dopamine Antagonists (Chlorpromazine, Compazine, etc.). Anything that interferes with dopamine levels can easily diminish T levels. These psychotropics are no exceptions.
NOTE: I cover some of the famous "anti-aphrodisiac", libido-reducing medications at the bottom of my link on Male Libido Supplements.
9. Antihypertensives (Beta Blockers). Several studies have shown that beta blockers, a very common class of medications for high blood pressure can lower testosterone. For example one study found that atenolol, metoprolol, pindolol and propranolol all led to decreased testosterone levels. Propranolol was found the above study to be the worst. 
Did you know you can inexpensively do your own testing for many hormones? The industry leaders is Discounted Labs..
10. Valium (Diazepam). One theme you may have noticed: almost any medication that affects the brain and/or brain function significantly tends to lower testosterone. Valium, the famous tranqualizer, is no exception and appears to tranqulize the testes as well. 
CAUTION: There are a wide variety of toxins, pesticides, endocrine disruptors, xenoestrogens, excitotoxins and other chemicals that can be considered "drugs" even though they are not pharmaceuticals. I give significant coverage to these on my site at this link on Nasty Chemicals That Can Lower Testosterone.
11. Anticonvulsants. These drugs commonly used to treat epilepsy lead to an interesting phenomenon: an increase in total testosterone but a decrease in free testosterone.  This situation arises from an increase in SHBG. So who wins? The increased total T or the decreased free? Unfortunately, in the above study, the loss of free testosterone correlated well with decreased sexual activity levels.
12. Tagamet (Cimitidine). Strange as it may seem, this H2 Agonist Blocker for stomach issues actually directly lowers testosterone production.  In fact, one animal study labelled it as an antiandrogen.  Can't be any more clear that that, eh?
13. Antidepressants (SSRI's). SSRI's are notorious for lowering libido and leading to sexual dysfunction in both men and women. Depression itself is notorious for lowering testosterone, something I discuss in my link on Depression and Testosterone, likely due to its increase in cortisol levels as a stressor. This makes it difficult to tease out if SSRI's actually lower testosterone, since it is a side effect of the very illness these medications are trying to treat. And, indeed, one study actually found that SSRI's may increase T levels in men. 
However, more recent research showed very much the opposite. Some studies have shown that most SSRI's significantly affect liver enzymes and thus some postulate that they slow down the time to clear estrogen (estradiol), i.e. allow for estradiol to build up.  One report noticed a wide variety of SSRI's that resulted in lower free T levels as well. 
But the most damning evidence came from studies on Prozac, which shows that, particularly in those who use it longer term, that testosterone levels do tend to drop. See my page on Testosterone and Prozac for more information.
1) http://www.umm.edu/patiented/articles/ what_causes_hypothyroidism_000038_2.htm
3) Journal of Pain and Symptom Management, Feb 1994, 9(2):126 131, "Altered sexual function and decreased testosterone in patients receiving intraspinal opioids"
4) Current Opinion in Endocrinology & Diabetes, Jun 2006, 13(3):262-266, "Opioid-induced androgen deficiency"
6) Systems Biology in Reproductive Medicine, 1979, 3(1):31-35, "Effect of diazepam on serum testosterone and the ventral prostate gland in male rats"
7) Arch Sex Behav, 1988 Jun, 17(3):241-55, "Beta-blocker effects on sexual function in normal males"8) J Neurol Neurosurg Psychiatry, 1983, 46:824-826, "Sex hormones, sexual activity and plasma anticonvulsant levels in male epileptics"
9) Eur J Clin Pharmacol, 1985, 29(4):489-93, "Effect of a single administration of ketoconazole on total and physiologically free plasma testosterone and 17 beta-oestradiol levels in healthy male volunteers"
10) Arch Intern Med. 1985;145(5):920-922, "Cimetidine Blocks Testosterone Synthesis"
11) Gastroenterology, 1979, 76(3):504-508, "Cimetidine is an antiandrogen in the rat"
12) Journal of psychosomatic research, 03/2012, 72(3):205-13, "Salivary testosterone: associations with depression, anxiety disorders, and antidepressant use in a large cohort study"
13) European Neuropsychopharmacology, Apr 2006, 16(3):178 186, "The effect of tricyclic antidepressants, selective serotonin reuptake inhibitors (SSRIs) and newer antidepressant drugs on the activity and level of rat CYP3A"
16) Drug Metab Dispos, 2001 Jun, 29(6):837-42, "Clotrimazole is a selective and potent inhibitor of rat cytochrome P450 3A subfamily-related testosterone metabolism"