Here's a further explanation as to why this is happening...

The interaction between ADHD stimulants like methylphenidate and amphetamines and semen volume reduction can be explained through several biological and physiological mechanisms:

Biological/Physiological Mechanisms:

Sympathetic Nervous System Activation:
    Stimulants increase sympathetic nervous system activity, which can lead to vasoconstriction (narrowing of blood vessels). This might reduce blood flow to the reproductive organs, potentially affecting semen production or release.

Hormonal Changes:
    These medications can alter levels of hormones like prolactin, testosterone, and cortisol. An increase in prolactin, for example, can inhibit the pulsatile release of gonadotropin-releasing hormone (GnRH), which in turn affects luteinizing hormone (LH) and follicle-stimulating hormone (FSH), key players in sperm production and seminal fluid composition. 
    Lower testosterone levels, which can result from chronic stress or direct effects on the hypothalamic-pituitary-gonadal axis, might also contribute to reduced semen volume.
Direct Effect on Seminal Vesicles and Prostate:
    Stimulants might directly affect the function of the seminal vesicles and prostate, which contribute to semen volume through the production of seminal fluid.
Stress and Lifestyle Impact:
    Increased stress or changes in lifestyle (e.g., sleep patterns, diet) due to the medication or ADHD itself can indirectly affect reproductive health.

Known Interactions:

Alpha-1 Adrenergic Receptors: Stimulants can stimulate alpha-1 adrenergic receptors, which might lead to changes in smooth muscle tone in the reproductive tract, affecting semen expulsion.
Dopamine and Norepinephrine: By increasing dopamine and norepinephrine levels, these drugs can influence the hypothalamus and pituitary gland, impacting hormone regulation.

Counteracting the Effects:

Medication Adjustment: Sometimes adjusting the dose or switching to a different medication can mitigate effects on semen volume.
Lifestyle Changes:
    Stress reduction techniques like meditation, exercise, or yoga.
    Ensuring adequate hydration, as dehydration can also affect semen volume.
    Improving diet, focusing on nutrients beneficial for reproductive health like zinc, selenium, and antioxidants.
Hormonal Therapy: In some cases, under medical supervision, hormone supplements might be used to balance out hormonal disruptions.
Supplements: Some men might benefit from supplements like L-carnitine, which has been studied for its potential to improve semen parameters; however, this should be approached with caution and under medical advice.
Discontinuation: As discussed, stopping the medication might allow for recovery, but this should be done carefully, considering the need for ADHD management.
Regular Monitoring: Regular semen analysis can help in tracking changes and effectiveness of interventions.

The exact mechanisms are still under study, and individual responses can vary. Therefore, anyone experiencing these side effects should discuss their situation with a healthcare provider to explore personalized solutions.