Sildenafil vs Tadalafil in NZ: Which ED Medication Suits You?

If you've decided to do something about erectile difficulties, the first practical decision is which medication. In NZ that almost always comes down to sildenafil (the generic of Viagra) or tadalafil (the generic of Cialis). Both are PDE5 inhibitors — they work by the same mechanism — but they behave noticeably differently in real life, and which one suits you depends on how often you have sex, how much spontaneity you want, and what other medicines you're on.

This is a NZ doctor's plain-English comparison, written for men trying to make an actual treatment decision, not a marketing piece.

How they both work

Erections start with arousal in the brain. A signal travels down to the penis, releases nitric oxide in the smooth muscle of the corpora cavernosa, which raises cGMP, which relaxes the smooth muscle and allows blood to fill. PDE5 is the enzyme that breaks cGMP down — so blocking PDE5 keeps cGMP elevated for longer and makes it easier to get and maintain an erection.

Both sildenafil and tadalafil are PDE5 inhibitors. Without arousal, neither does anything — the drug doesn't manufacture an erection, it just removes the brake that prevents one. That's the most important misunderstanding to clear up: these are not aphrodisiacs.

Sildenafil (generic Viagra)

• Onset: ~30–60 minutes after a dose
• Duration: 4–6 hours of clinical effect
• Half-life: ~4 hours
• Common doses (NZ): 25, 50, 100 mg — typically taken as needed, before planned sexual activity
• Food: Effect blunted by a heavy or high-fat meal. Take on an empty or light stomach for fastest onset.
• Regulatory status (NZ): Prescription medicine. Pharmacist-only supply (without a doctor's script) is permitted in limited circumstances under Medsafe rules — confirm with a pharmacist what's available locally.

Sildenafil was the original PDE5 inhibitor — approved in the late 1990s — and most NZ men starting ED treatment have been on it at some point. It works, it's predictable, and it's well-tolerated. The trade-off is timing: you take a tablet, wait 45 minutes to an hour, and have a 4–6 hour window to act. For some couples that's fine. For others the planning kills the mood.

Tadalafil (generic Cialis)

• Onset: ~30 minutes (faster than sildenafil for some men, similar for others)
• Duration: Up to 36 hours of clinical effect from a single on-demand dose
• Half-life: ~17.5 hours (much longer than sildenafil)
• Common doses (NZ):
  • On-demand: 10 or 20 mg before planned activity
  • Daily low-dose: 2.5 or 5 mg once a day — keeps you continuously responsive
• Food: Effect is not meaningfully affected by food. You can eat normally.
• Regulatory status (NZ): Prescription medicine.

Tadalafil's long duration is the headline feature. A single 10 or 20 mg dose covers a long weekend; the daily low-dose 5 mg pattern removes planning altogether — you're simply always responsive when arousal happens. Tadalafil daily is also licensed for lower urinary tract symptoms (LUTS) from benign prostatic hyperplasia (BPH), so it sometimes addresses two problems at once in older men.

Side-by-side

Who suits which

A reasonable starting framework:

• Sex less than once a week, planned encounters, no BPH symptoms: Sildenafil on-demand. Cheap, predictable, half-tab if it's enough, full tab if it isn't.
• Sex more than twice a week, value spontaneity: Tadalafil daily 5 mg. The dose stays in your system; you're simply responsive when needed, with no tablet-timing involved.
• Want long-window flexibility without daily dosing: Tadalafil 10–20 mg on-demand — a Saturday-morning dose covers the weekend.
• You also have BPH symptoms (urinary hesitancy, weak stream, nocturia): Tadalafil daily 5 mg — addresses both.
• You're sensitive to PDE5 side effects (flushing, headache, nasal congestion): start with a lower dose of whichever — sildenafil 25 mg or tadalafil 10 mg — and titrate up only if needed.

Both medications are very effective for the majority of men with mild-to-moderate ED. They are not equally effective for everyone, and trial-and-error is normal — it's reasonable to try one for 4–6 attempts at the correct dose before deciding it isn't working for you.

Combining with TRT

If you're on TRT and still have ED symptoms, the cause is usually not insufficient testosterone. Once testosterone is in the normal range, the residual ED is most often vascular, neurological, or psychological — and PDE5 inhibitors are first-line.

Tadalafil daily 5 mg is often the cleanest add-on for men on TRT: it removes timing variables, addresses any BPH overlap if present, and works alongside the testosterone restoration. There is no clinical interaction between sildenafil or tadalafil and any of the funded testosterone formulations.

Side effects

Both drugs share the same side-effect profile, with frequency varying by dose:

• Common: Headache, facial flushing, nasal congestion, indigestion. Usually mild and dose-related; often settles within a few uses.
• Less common: Back or muscle ache (more with tadalafil — usually settles within 24 hours), visual changes (bluish tint, brightness — more with sildenafil and uncommon), tinnitus.
• Rare but serious: Priapism (an erection lasting more than 4 hours — a medical emergency, go to ED), sudden hearing loss, NAION (a non-arteritic anterior ischaemic optic neuropathy — sudden vision loss in one eye, very rare).

If either causes significant adverse symptoms, the answer is usually to try the other one — many men tolerate one well and the other poorly.

Interactions you must know about

The single most important interaction is nitrates. PDE5 inhibitors combined with nitrates (GTN spray or tablets for angina, isosorbide mononitrate or dinitrate) cause dangerous hypotension — this combination has caused deaths. Absolute contraindication.

• Never take sildenafil or tadalafil if you use nitrates for chest pain.
• Don't take a nitrate within 24 hours of a sildenafil dose, or within 48 hours of a tadalafil dose. Tell paramedics if you've taken either and they're considering GTN.

Other interactions to flag with your prescriber:

• Alpha-blockers (tamsulosin, doxazosin for BPH or hypertension) — can cause additive blood-pressure drop; usually manageable with timing and dose adjustment.
• CYP3A4 inhibitors (ketoconazole, erythromycin, ritonavir, grapefruit juice in large amounts) — slow the drug's metabolism, raising effective dose.
• Riociguat (a pulmonary hypertension drug) — contraindicated.

When PDE5 inhibitors don't work

If the maximum tolerated dose of one PDE5 inhibitor doesn't produce a usable erection, the answer is usually not to keep increasing the dose. The workup shifts to:

• Cardiovascular assessment (ED is often the first warning sign of vascular disease)
• Testosterone bloods (especially if libido is also low)
• Diabetes / metabolic screen
• Medication review (SSRIs, beta-blockers and other commonly-prescribed drugs can drive ED)
• Psychological factors — particularly relevant if you wake with morning erections but can't perform with a partner

Beyond PDE5 inhibitors, the second-line options in NZ include intracavernosal injection (alprostadil), vacuum erection devices, and surgical options for refractory cases. We can refer to urology when needed.

A separate category worth flagging: porn-induced ED (PIED) in younger men. If you're under 40, get morning erections, can perform solo but not with a partner, the cause is often not pharmacological. See the PIED article.

What we do at Enhanced Men

For men presenting with ED:

• Workup first — quick assessment of cardiovascular risk, testosterone status, medications, and pattern of dysfunction. Identifying the cause matters more than picking the tablet.
• PDE5 inhibitor script — sildenafil or tadalafil at the appropriate starting dose, with a clear titration plan
• Daily tadalafil for men who'd benefit (frequency, BPH overlap, want spontaneity)
• Referral when ED is a flag for vascular disease or when first-line treatment isn't working

The consult is the cost. The medication itself is on the standard NZ prescription pathway.

FAQ

Can I get sildenafil over the counter in NZ? Pharmacist-only supply of sildenafil exists in limited circumstances under Medsafe rules — depends on dose, history and screening. For most men a prescription is the practical route, particularly when there are cardiovascular risk factors or other medications involved.

Can I take both sildenafil and tadalafil? No — never combine PDE5 inhibitors. Use one at a time. If switching between them, leave at least the longer drug's half-life clearance period (24–36 hours after a tadalafil dose before taking sildenafil).

Will I become dependent on them? PDE5 inhibitors are not addictive. They don't change your underlying erectile function. Many men use them initially for confidence, find performance returns with successful encounters, and reduce or stop without difficulty.

Can I drink alcohol with them? Moderate alcohol is fine. Heavy alcohol on its own reduces erectile function — the drug won't override that.

How long can I take them for? Long-term daily tadalafil has been studied for years in BPH populations without safety signals. On-demand sildenafil has decades of post-marketing data. Both are appropriate for ongoing use under prescription.

What about the recreational use angle? PDE5 inhibitors are sometimes used recreationally, including stacked with stimulants. This is a meaningfully different risk profile — cardiovascular events have been reported. We don't support or prescribe for this use case.

References (NZ-specific)

• New Zealand Formulary — sildenafil monograph (nzf.org.nz)
• New Zealand Formulary — tadalafil monograph (nzf.org.nz)
• Medsafe NZ — Viagra (sildenafil) data sheet
• Medsafe NZ — Cialis (tadalafil) data sheet
• European Association of Urology — EAU Guidelines on Male Sexual Dysfunction
• British Society for Sexual Medicine — Guidelines on the Management of Erectile Dysfunction

This article is general health information and does not replace personalised medical advice. ED can be a sign of underlying cardiovascular, hormonal or psychological conditions that need a clinical assessment, not just a script — particularly if it's new, progressive, or appearing before 50.