Impotence, or erectile dysfunction, or ED, means the inability of man to get and sustain an erection of the penis that is firm enough for sexual intercourse. A multitude of psychological and physical factors play into erections. Various prescription medications and legal and illegal drugs can inhibit the pathways of sexual response, causing erectile dysfunction.
Blood Pressure Medication
Sexual excitement causes blood to flood into the penis, filling spongy spaces called the corpora cavernosa. The increased blood pressure in the penis causes an erection and temporarily traps the blood to sustain it. Any factor that compromises blood flow to the penis, including some medications that lower blood pressure to treat hypertension, or high blood pressure, can cause ED. The Merck Manual lists specific blood pressure drugs like clonidine and spironolactone as well as broad classes like beta blockers and thiazides that can cause ED. In addition to lowering blood pressure, spironolactone interferes with receptors that bind to testosterone, a major component of the male sexual response. Beta blockers, including acebutolol and nadolol among others, open blood vessels and dampen the force and rate of the heartbeat. Thiazides are a type of diuretics, medications that remove excess water from the blood. Lower blood volume means lower blood pressure. Examples of thiazides include chlorothiazide and metolazone.
Central Nervous System Drugs
The brain is integrally involved in producing an erection. Sexual thoughts processed by the cortex of the brain and spinal nerves combine to stimulate the production and release of nitric oxide in the penis. Nitric oxide relaxes smooth muscles in the corpora cavernosa, opening them to a massive influx of blood that causes an erection. Anti-depressants like monoamine oxidase inhibitors, or MAOIs, selective serotonin re-uptake inhibitors, or SSRIs, and tricyclics interfere with the brain areas that control the sex drive or libido and often can cause ED.
Other Medications
The Merck Manual lists other medications that commonly cause ED. Chemotherapy drugs and anticholinergic drugs can inhibit erections. Drugs that affect testosterone levels such as GnRH analogues, anti-androgens and estrogens can decrease sex drive and lead to ED.
Recreational Drugs
The Mayo Clinic says that use of alcohol and tobacco can cause ED. Long-term heavy use of alcohol is especially risky because it acts as a depressant in the central nervous system and is associated with other risk factors for ED like heart disease. Long-term tobacco uses interferes with the ability to get and sustain an erection because over time, tobacco damages blood vessels, hardening their walls and narrowing their diameter. The Merck Manual says that artherosclerosis of the arteries of the penis commonly causes ED. Cocaine's effects on the central nervous system can inhibit erections, and amphetamines can also cause ED.
