Yes, for some
adults (mature minors are ineligible in this particular case) presenting with a psychiatric condition, it is possible to access euthanasia if a physician determines that they meet all of the criteria outlined under the law. However, it is not a quick and clear cut procedure and it is even stated that euthanasia is
not a right and that a physician is
free to refuse:
"L'euthanasie n'est cependant pas un droit : introduire une demande d'euthanasie ne garantit pas que celle-ci soit pratiquée. Même si toutes les conditions légales sont réunies, le médecin est libre d'accepter ou de refuser de pratiquer une euthanasie. S'il refuse, il est tenu d'en informer en temps utile le patient ou la personne de confiance éventuelle en précisant les raisons de son choix. Le patient peut alors se tourner vers un autre médecin."
In the case of those suffering from mental illnesses, there are multiple assessments and one is usually required to wait for months before receiving a response. It is not something that is taken lightly and there is special care take to ensure that a patient's condition is in fact irredeemable.
Injection, huh? I hate needles.
In most jurisdictions where euthanasia is available, there is usually an option for oral administration of the medications used in ending the patient's life. In Belgium specifically, there is even a recipe that makes the oral formulation of barbiturates more palatable (ex: sugary syrups, star anise etc). In these regimens, metoclopramide is also the antiemetic of choice and I suspect that this is why it appears in the Peaceful Pill Handbook.